Publications | Matter Assembly Computation Lab

2024

Mechanical Characterization and Constitutive Modeling of 3D Printable Soft Materials

Lawrence Smith, and Robert MacCurdy

3D Printing and Additive Manufacturing, 2024

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Numerical modeling of soft matter has the potential to enable exploration of the soft robotic field’s next frontier: human/machine cooperative design. However, access to material models suitable for predicting the behavior of soft matter is limited, and analysts typically conduct their own mechanical characterization on every new material they work with. In this work we present detailed mechanical characterization of 14 3D-printable soft materials suitable for fabricating soft robots. To allow the extension of this work by other researchers, our test procedures, raw data, constitutive model coefficients, and code used for curve fitting is freely available at www.SoRoForge.com.
@article{doi:10.1089/3dp.2023.0010, author = {Smith, Lawrence and MacCurdy, Robert}, title = {Mechanical Characterization and Constitutive Modeling of 3D Printable Soft Materials}, journal = {3D Printing and Additive Manufacturing}, volume = {11}, number = {3}, pages = {e1209-e1212}, year = {2024}, doi = {10.1089/3dp.2023.0010}, url = {https://doi.org/10.1089/3dp.2023.0010}, eprint = {https://doi.org/10.1089/3dp.2023.0010} }

Membrane-Assisted Thermal Inkjet (MA-TIJ) Droplet Ejection for TIJ-Incompatible Inks

Brandon Hayes, Heiko Kabutz, Kaushik Jayaram, and Robert MacCurdy

Bulletin of the American Physical Society, 2024

@article{hayes2024membrane,
  title = {Membrane-Assisted Thermal Inkjet (MA-TIJ) Droplet Ejection for TIJ-Incompatible Inks},
  author = {Hayes, Brandon and Kabutz, Heiko and Jayaram, Kaushik and MacCurdy, Robert},
  journal = {Bulletin of the American Physical Society},
  year = {2024},
  publisher = {APS}
}

High-Accuracy Global Wildlife Tracking With Small Satellites

Zachary Manchester, Robert MacCurdy, Fausto Vega, Jacob Levenson, and James Phillips

In 2024 Ocean Sciences Meeting, 2024

Bib

@inproceedings{manchester2024high,
  title = {High-Accuracy Global Wildlife Tracking With Small Satellites},
  author = {Manchester, Zachary and MacCurdy, Robert and Vega, Fausto and Levenson, Jacob and Phillips, James},
  booktitle = {2024 Ocean Sciences Meeting},
  year = {2024},
  organization = {AGU}
}

An Architecture Study for Low-Power Satellite-Based Wildlife Tracking

Fausto Vega, James Phillips, Kathryn Lampo, Robert MacCurdy, and Zachary Manchester

In 2024 IEEE Aerospace Conference, 2024

DOI Bib

@inproceedings{10521172,
  author = {Vega, Fausto and Phillips, James and Lampo, Kathryn and MacCurdy, Robert and Manchester, Zachary},
  booktitle = {2024 IEEE Aerospace Conference},
  title = {An Architecture Study for Low-Power Satellite-Based Wildlife Tracking},
  year = {2024},
  volume = {},
  number = {},
  pages = {1-15},
  keywords = {Time-frequency analysis;Costs;Satellite broadcasting;Radio transmitters;Wildlife;Small satellites;Transportation},
  doi = {10.1109/AERO58975.2024.10521172}
}

Characterization of organic fouling on thermal bubble-driven micro-pumps

Brandon Hayes, Cillian Murphy, Janeth Marquez Rubio, Daimean Solis, Kaushik Jayaram, and 1 more author

Biofouling, 2024

Bib

@article{hayes2024characterization,
  title = {Characterization of organic fouling on thermal bubble-driven micro-pumps},
  author = {Hayes, Brandon and Murphy, Cillian and Marquez Rubio, Janeth and Solis, Daimean and Jayaram, Kaushik and MacCurdy, Robert},
  journal = {Biofouling},
  pages = {1--15},
  year = {2024},
  publisher = {Taylor \& Francis}
}

OpenVCAD: An open source volumetric multi-material geometry compiler

Charles Wade, Graham Williams, Sean Connelly, Braden Kopec, and Robert MacCurdy

Additive Manufacturing, 2024

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Modern additive manufacturing has made significant advancements in multi-material fabrication techniques that allow for position-specific control of material deposition. With these advancements, design tools have fallen behind machine capabilities in specifying volumetric information. Traditionally, design and fabrication workflows have expressed multi-material objects as several single-material bodies. By storing only the information about the surfaces of the geometries, information about the volumetric composition of the solids is unrepresented. The intense interest in compliant mechanisms and meta-materials demands a new design method that can support architecting material distribution throughout an object. To address these needs, we present OpenVCAD, an open-source volumetric design compiler with multi-material capabilities. OpenVCAD provides a scriptable suite of geometric and material design methods that enable efficient representation of object with complex geometry and material distributions. OpenVCAD allows functional specification of multi-material volumes that are parameterized on spatial locations, yielding complex multi-material distributions that would be impossible to describe using alternative methods. This paper will present the OpenVCAD pipeline, compare it to related work, and demonstrate its use through the design and manufacturing of functionally graded multi-material components.
@article{OpenVCAD, title = {OpenVCAD: An open source volumetric multi-material geometry compiler}, journal = {Additive Manufacturing}, pages = {103912}, year = {2024}, issn = {2214-8604}, doi = {https://doi.org/10.1016/j.addma.2023.103912}, url = {https://www.sciencedirect.com/science/article/pii/S2214860423005250}, author = {Wade, Charles and Williams, Graham and Connelly, Sean and Kopec, Braden and MacCurdy, Robert}, keywords = {Volumetric design, Multi-material additive manufacturing, Meta-materials, Lattice-structures, InkJet 3D printing, Functional grading}, }
Tunable Metamaterials for Impact Mitigation

Advanced Materials Technologies, 2024

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Abstract Traditional methods of shielding fragile goods and human tissues from impact energy rely on isotropic foam materials. The mechanical properties of these foams are inferior to an emerging class of metamaterials called plate lattices, which have predominantly been fabricated in simple 2.5-dimensional geometries using conventional methods that constrain the feasible design space. In this work, additive manufacturing is used to relax these constraints and realize plate lattice metamaterials with nontrivial, locally varying geometry. The limitations of traditional computer-aided design tools are circumvented and allow the simulation of complex buckling and collapse behaviors without a manual meshing step. By validating these simulations against experimental data from tests on fabricated samples, sweeping exploration of the plate lattice design space is enabled. Numerical and experimental tests demonstrate plate lattices absorb up to six times more impact energy at equivalent densities relative to foams and shield objects from impacts ten times more energetic while transmitting equivalent peak stresses. In contrast to previous investigations of plate lattice metamaterials, designs with nonuniform geometric prebuckling in the out-of-plane direction is explored and showed that these designs exhibit 10% higher energy absorption efficiency on average and 25% higher in the highest-performing design.
@article{https://doi.org/10.1002/admt.202301668, year = {2024}, publisher = {Wiley-VCH GmbH}, author = {}, title = {Tunable Metamaterials for Impact Mitigation}, journal = {Advanced Materials Technologies}, volume = {n/a}, number = {n/a}, pages = {2301668}, keywords = {additive manufacturing, computational design, impact mitigation, metamaterials}, doi = {https://doi.org/10.1002/admt.202301668}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admt.202301668}, eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/admt.202301668}, }
Digital Multiphase Composites via Additive Manufacturing

Lawrence T. Smith, and Robert B. MacCurdy

Advanced Materials, 2024

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Abstract Mechanical properties of traditional engineering materials are typically coupled to each other, presenting a challenge to practitioners with multi-dimensional material property requirements. In this work, continuous, independent control over multiple mechanical properties is demonstrated in composite materials realized using additive manufacturing. For the first time, composites additively manufactured from rigid plastic, soft elastomer, and liquid constituents are experimentally characterized, demonstrating materials which span four orders of magnitude in modulus and two orders of magnitude in toughness. By forming analytical mappings between relative concentrations of constituents at the microscale and resulting macroscale material properties, inverse material design is enabled; the method is showcased by printing artifacts with prescribed toughness and elasticity distributions. The properties of these composites are placed in the context of biological tissues, showing they have promise as mechanically plausible tissue mimics.
@article{https://doi.org/10.1002/adma.202308491, year = {2024}, publisher = {Wiley-VCH GmbH}, author = {Smith, Lawrence T. and MacCurdy, Robert B.}, title = {Digital Multiphase Composites via Additive Manufacturing}, journal = {Advanced Materials}, volume = {n/a}, number = {n/a}, pages = {2308491}, keywords = {additive manufacturing, digital composites, material characterization, multiphase materials}, doi = {https://doi.org/10.1002/adma.202308491}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202308491}, eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202308491}, }

2023

An OpenFOAM framework to model thermal bubble-driven micro-pumps

Whiting G. L. Hayes B., and MacCurdy R.

Physics of Fluids, Jun 2023

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Thermal bubble-driven micro-pumps (also known as inertial pumps) are an upcoming micro-pump technology that can be integrated directly into micro/mesofluidic channels to displace fluid without moving parts. These micro-pumps are high-power resistors that locally vaporize a thin layer of fluid above the resistor surface to form a high-pressure vapor bubble which performs mechanical work. Despite their geometric simplicity, thermal bubble-driven micro-pumps are complex to model due to the multiphysics couplings of Joule heating, thermal bubble nucleation, phase change, and multiphase flow. As such, most simulation approaches simplify the physics by neglecting Joule heating, nucleation, and phase change effects as done in this study. To date, there are no readily available, reduced physics open-source modeling tools that can resolve both pre-collapse (defined as when the bubble is expanding and collapsing) and post-collapse (defined as when the bubble has re-dissolved back into the subcooled fluid) bubble and flow dynamics. In this study, an OpenFOAM framework for modeling thermal bubble-driven micro-pumps is presented, validated, and applied. The developed OpenFOAM model agrees with both experimental data and commercial computational fluid dynamics (CFD) software, FLOW-3D. Additionally, we assess the shape of the transient velocity profile during a pump cycle for the first time and find that it varies substantially from theoretical Poiseuille flow during pre-collapse but is within 25\% of the theoretical flow profile during post-collapse. We find that this deviation is due to flow never becoming fully developed during each pump cycle. We envision the developed OpenFOAM framework as an open-source CFD toolkit for microfluidic designers to simulate devices with thermal bubble-driven micro-pumps.
@article{10.1063/5.0155615, year = {2023}, publisher = {Phys. Fluids 10.1063/5.0155615}, author = {Hayes B., Whiting G. L. and R., MacCurdy}, title = {An OpenFOAM framework to model thermal bubble-driven micro-pumps}, journal = {Physics of Fluids}, volume = {35}, number = {6}, pages = {062013}, month = jun, issn = {1070-6631}, doi = {10.1063/5.0155615}, url = {https://doi.org/10.1063/5.0155615}, eprint = {https://pubs.aip.org/aip/pof/article-pdf/doi/10.1063/5.0155615/18016336/062013\_1\_5.0155615.pdf} }

2022

Rapid Fabrication of Low-Cost Thermal Bubble-Driven Micro-Pumps

Micromachines, Jun 2022

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Thermal bubble-driven micro-pumps are an upcoming actuation technology that can be directly integrated into micro/mesofluidic channels to displace fluid without any moving parts. These pumps consist of high power micro-resistors, which we term thermal micro-pump (TMP) resistors, that locally boil fluid at the resistor surface in microseconds creating a vapor bubble to perform mechanical work. Conventional fabrication approaches of thermal bubble-driven micro-pumps and associated microfluidics have utilized semiconductor micro-fabrication techniques requiring expensive tooling with long turn around times on the order of weeks to months. In this study, we present a low-cost approach to rapidly fabricate and test thermal bubble-driven micro-pumps with associated microfluidics utilizing commercial substrates (indium tin oxide, ITO, and fluorine doped tin oxide, FTO, coated glass) and tooling (laser cutter). The presented fabrication approach greatly reduces the turn around time from weeks/months for conventional micro-fabrication to a matter of hours/days allowing acceleration of thermal bubble-driven micro-pump research and development (R&D) learning cycles.
@article{mi13101634, year = {2022}, publisher = { Emerging Micro and Nano Technologies in Advanced Point of Care (POC) Innovations}, author = {}, title = {Rapid Fabrication of Low-Cost Thermal Bubble-Driven Micro-Pumps}, journal = {Micromachines}, volume = {13}, number = {10}, article-number = {1634}, url = {https://www.mdpi.com/2072-666X/13/10/1634}, pubmedid = {36295987}, issn = {2072-666X}, doi = {10.3390/mi13101634}, }
Liquid–solid co-printing of multi-material 3D fluidic devices via material jetting

Brandon Hayes, Travis Hainsworth, and Robert MacCurdy

Additive Manufacturing, Jun 2022

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Multi-material material jetting additive manufacturing processes deposit micro-scale droplets of different model and support materials to build three-dimensional (3D) parts layer by layer. Recent efforts have demonstrated that liquids can act as support materials, which can be easily purged from micro/milli-channels, and as working fluids, which permanently remain in a structure, yet the lack of a detailed understanding of the print process and mechanism has limited widespread applications of liquid printing. In this study, an “all in one go” multi-material print process, herein termed liquid–solid co-printing in which non photo-curable and photo-curable liquid droplets are simultaneous deposited, is extensively characterized. The mechanism of liquid–solid co-printing is explained via experimental high speed imaging and computational fluid dynamic (CFD) studies. This work shows that a liquid’s surface tension can support jetted photopolymer micro-droplets which photo-polymerize on the liquid surface to form a solid layer of material. Design rules for liquid–solid co-printing of micro/milli-fluidic devices are presented as well as case studies of planar, 3D, and multi-material micro/mesofluidic structures such as mixers, droplet generators, highly branching structures, and an integrated one-way flap valve. We envision the liquid–solid co-printing process as a key new capability in additive manufacturing to enable simple and rapid fabrication of 3D, integrated print-in-place multi-material fluidic circuits and hydraulic structures with applications including micro/mesofluidic circuits, electrochemical transistors, lab-on-a-chip devices, and robotics.
@article{HAYES2022102785, year = {2022}, publisher = {Additive Manufacturing}, author = {Hayes, Brandon and Hainsworth, Travis and MacCurdy, Robert}, title = {Liquid–solid co-printing of multi-material 3D fluidic devices via material jetting}, journal = {Additive Manufacturing}, volume = {55}, pages = {102785}, issn = {2214-8604}, doi = {https://doi.org/10.1016/j.addma.2022.102785}, url = {https://www.sciencedirect.com/science/article/pii/S2214860422001890}, keywords = {Additive manufacturing, Mesofluidics, Modeling and simulation, Multi-material, Material jetting}, }
Stretching the Boundary: Shell Finite Elements for Pneumatic Soft Actuators

Lawrence Smith, Jacob Haimes, and Robert MacCurdy

In 2022 IEEE 5th International Conference on Soft Robotics (RoboSoft), Jun 2022

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Many soft robotics researchers use numerical simulation; all of them wish their simulations would run faster. In this paper we highlight an attractive option for simulating pneumatic soft actuator designs: zero-thickness shell finite elements. These offer a favorable balance between predictive accuracy and computational cost relative to standard approaches. We find that shell finite elements offer a 7x reduction in analysis time while accurately predicting the behavior of a wide variety of soft actuators. The benefits conferred by shell finite element analysis are especially valuable in contexts where simulation speed is as important as absolute accuracy, such as automated design, optimization, and real-time control.
@inproceedings{9762108, year = {2022}, publisher = {IEEE 5th International Conference on Soft Robotics}, author = {Smith, Lawrence and Haimes, Jacob and MacCurdy, Robert}, booktitle = {2022 IEEE 5th International Conference on Soft Robotics (RoboSoft)}, title = {Stretching the Boundary: Shell Finite Elements for Pneumatic Soft Actuators}, volume = {}, number = {}, pages = {403-408}, doi = {10.1109/RoboSoft54090.2022.9762108}, }
Simulating Electrohydraulic Soft Actuator Assemblies Via Reduced Order Modeling

Travis Hainsworth, Ingemar Schmidt, Vani Sundaram, Gregory L. Whiting, Christoph Keplinger, and 1 more author

In 2022 IEEE 5th International Conference on Soft Robotics (RoboSoft), Jun 2022

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Soft robots compliment traditional rigid robots by expanding their capabilities to interact with the physical world. A robot made with compliant, soft materials can benefit from their inherent continuum mechanics to achieve interactions with the environment that a rigid robot may find difficult. This can include grasping delicate objects, navigating through variable terrain, or working alongside humans in a safer manner. The flexible, adaptable nature of soft robots provide these benefits, but they also make predicting their actuated response a difficult, computationally-intensive task. Here we provide a non-linear, reduced order model informed by collected data on hydraulically amplified self-healing electrostatic actuators (HASELs). With this reduced order model, we simulate robots comprised of multiple actuators in an effort to rapidly eval- uate potential design candidates without the need for time- consuming manufacturing. The simulation leverages a reduced- order model of HASELs based on a parallel mass spring damper (MSD) representation, made of two non-linear springs, and a damper; this data-driven parameter identification aids model fidelity. We construct a robotic manipulator actuated via six HASELs and show that the simulations driven by the non-linear MSD models accurately predict the robot’s physical behavior on a macro scale. While this work focuses on a specific actuator type, the approach shown here could be extended to other linearly expanding soft actuators. Using this method, soft robotic assemblies actuated via HASELs can be rapidly evaluated in simulation before a laborious manufacturing process, which in turn will allow for faster design iterations to create more effective robots.
@inproceedings{9762073, year = {2022}, publisher = {IEEE 5th International Conference on Soft Robotics}, author = {Hainsworth, Travis and Schmidt, Ingemar and Sundaram, Vani and Whiting, Gregory L. and Keplinger, Christoph and MacCurdy, Robert}, booktitle = {2022 IEEE 5th International Conference on Soft Robotics (RoboSoft)}, title = {Simulating Electrohydraulic Soft Actuator Assemblies Via Reduced Order Modeling}, volume = {}, number = {}, pages = {21-28}, doi = {10.1109/RoboSoft54090.2022.9762073} }
Automated Synthesis of Bending Pneumatic Soft Actuators

Lawrence Smith, Travis Hainsworth, Jacob Haimes, and Robert MacCurdy

In 2022 IEEE 5th International Conference on Soft Robotics (RoboSoft), Jun 2022

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Soft robotics embraces the design philosophy of function through morphology. Therefore defining the affordances of a soft robotic structure is equivalent to determining the composition and distribution of the materials that make up the robot. This design process has historically been dominated by human intuition and labor-intensive experimentation. However, the design space of multi-material continuum structures is infinite. Automation tools to accelerate soft robot design could enable new designs to be created on-demand, specific to a need, more rapidly and at lower cost than would be possible using human labor alone. In this work we formulate the soft robot design problem as a multi-objective optimization task. We demonstrate a design automation system for bending soft actuators which integrates multi-objective heuristic search with a powerful generative encoding that converts high level design goals, compliance and forcefulness in our case, into mechanical designs automatically. These designs can be directly fabricated using a 3-D printer. We compare numerous simulated results from our optimization and a physical instance fabricated via 3-D printing with a broad survey of contemporary results from the soft robotics literature.
@inproceedings{9762105, year = {2022}, publisher = {IEEE 5th International Conference on Soft Robotics}, author = {Smith, Lawrence and Hainsworth, Travis and Haimes, Jacob and MacCurdy, Robert}, booktitle = {2022 IEEE 5th International Conference on Soft Robotics (RoboSoft)}, title = {Automated Synthesis of Bending Pneumatic Soft Actuators}, volume = {}, number = {}, pages = {358-363}, doi = {10.1109/RoboSoft54090.2022.9762105}, }
Voxel Printing Anatomy: Design and Fabrication of Realistic, Presurgical Planning Models through Bitmap Printing

Nicholas M. Jacobson, Lawrence Smith, Jane Brusilovsky, Erik Carrera, Hayden McClain, and 1 more author

Journal of Visualized Experiments, Jun 2022

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Most applications of 3-dimensional (3D) printing for presurgical planning have been limited to bony structures and simple morphological descriptions of complex organs due to the fundamental limitations in accuracy, quality, and efficiency of the current modeling paradigm. This has largely ignored the soft tissue critical to most surgical specialties where the interior of an object matters and anatomical boundaries transition gradually. Therefore, the needs of the biomedical industry to replicate human tissue, which displays multiple scales of organization and varying material distributions, necessitate new forms of representation. Presented here is a novel technique to create 3D models directly from medical images, which are superior in spatial and contrast resolution to current 3D modeling methods and contain previously unachievable spatial fidelity and soft tissue differentiation. Also presented are empirical measurements of novel, additively manufactured composites that span the gamut of material stiffnesses seen in soft biological tissues from MRI and CT. These unique volumetric design and printing methods allow for deterministic and continuous adjustment of material stiffness and color. This capability enables an entirely new application of additive manufacturing to presurgical planning: mechanical realism. As a natural complement to existing models that provide appearance matching, these new models also allow medical professionals to "feel" the spatially varying material properties of a tissue simulant-a critical addition to a field in which tactile sensation plays a key role.
@article{Jacobson2022, year = {2022}, publisher = {JoVE Journal of Visualized Experiments}, author = {Jacobson, Nicholas M. and Smith, Lawrence and Brusilovsky, Jane and Carrera, Erik and McClain, Hayden and Maccurdy, Robert}, doi = {10.3791/63214}, file = {:C\:/Users/Lawrence/Dropbox/BIG SYNC/papers/jove-protocol-63214-voxel-printing-anatomy-design-fabrication-realistic-presurgical.pdf:pdf}, issn = {1940087X}, journal = {Journal of Visualized Experiments}, number = {February}, pages = {1--15}, pmid = {35225265}, title = {Voxel Printing Anatomy: Design and Fabrication of Realistic, Presurgical Planning Models through Bitmap Printing}, volume = {180}, }

2021

Electro-Osmotic Gripper Characterization for Layered Assembly

Cheryl Perich, Robert MacCurdy, Ashley Macner, Joni Mici, Paul Steen, and 1 more author

3D Printing and Additive Manufacturing, Jun 2021

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Layered assembly is a voxel-based additive manufacturing process that relies on parallel grasping of voxels to produce multi-material parts. Although there exists substantial diversity in mechanisms of gripping, there still exists a lack of consistency, accuracy, and efficacy in positioning very large numbers of milli-, micro-, and nano-scale objects. We demonstrate the use of parallel electro-osmotic grippers to selectively transport multiple millimeter-sized voxels simultaneously. In contrast to previous research focused on using arrays of droplets to grab a single substrate, each element in the array is individually controlled via capillary effects, which are, in turn, controlled by an electric field to create predetermined patterns of droplets to pick and place selected objects. The demonstrated fluidic pick-and-place method has two key advantages: It is suitable for transport of fragile and complex objects due to the lack of mechanical contact, and it easily parallelizes to arbitrary array sizes for massively parallel pick-and-place. This work demonstrates a 25-element parallel assembly of 1.5-mm spheres with 95–98% grasping reliability, in a variety of geometric patterns. Experimental performance was validated against both analytical and computational models. The results suggest that electro-osmotic droplet arrays may enable the additive manufacturing of multi-material objects containing millions of components in the same print bed.
@article{perich2021electro, year = {2021}, publisher = {Mary Ann Liebert, Inc., publishers 140 Huguenot Street, 3rd Floor New~…}, title = {Electro-Osmotic Gripper Characterization for Layered Assembly}, author = {Perich, Cheryl and MacCurdy, Robert and Macner, Ashley and Mici, Joni and Steen, Paul and Lipson, Hod}, journal = {3D Printing and Additive Manufacturing}, }
A Seamless Workflow for Design and Fabrication of Multimaterial Pneumatic Soft Actuators

Lawrence Smith, Travis Hainsworth, Zachary Jordan, Xavier Bell, and Robert MacCurdy

In 2021 IEEE 17th International Conference on Automation Science and Engineering (CASE), Jun 2021

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Soft robotic actuators offer a range of attractive features relative to traditional rigid robots including inherently safer human-robot interaction and robustness to unexpected or extreme loading conditions. Soft robots are challenging to design and fabricate, and most actuators are designed by trial and error and fabricated using labor-intensive multi-step casting processes. We present an integrated collection of software tools that address several limitations in the existing design and fabrication workflow for pneumatic soft actuators. We use implicit geometry functions to specify geometry and material distribution, a GUI-based software tool for interactive exploration of computational network representations of these implicit functions, and an automated tool for generating rapid simulation results of candidate designs. We prioritize seamless connectivity between all stages of the design and fabrication process, and elimination of steps that require human intervention. The software tools presented here integrate with existing capabilities for multimaterial additive manufacturing, and are also forward-compatible with emerging automated design techniques. The workflow presented here is intended as a community resource, and aimed at lowering barriers for the discovery of novel soft actuators by experts and novice users. The data gathered from human-interaction with this tool will be used by future automation tools to enable fully-automated soft actuator design based on high-level specifications.
@inproceedings{9551668, year = {2021}, publisher = {IEEE 17th International Conference on Automation Science and Engineering}, author = {Smith, Lawrence and Hainsworth, Travis and Jordan, Zachary and Bell, Xavier and MacCurdy, Robert}, booktitle = {2021 IEEE 17th International Conference on Automation Science and Engineering (CASE)}, title = {A Seamless Workflow for Design and Fabrication of Multimaterial Pneumatic Soft Actuators}, volume = {}, number = {}, pages = {718-723}, doi = {10.1109/CASE49439.2021.9551668}, }
Modeling of contactless bubble–bubble interactions in microchannels with integrated inertial pumps

B. Hayes, G. L. Whiting, and R. MacCurdy

Physics of Fluids, Jun 2021

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In this study, the non-linear effect of contactless bubble-bubble interactions in inertial micro-pumps is characterized via reduced parameter one-dimensional and three-dimensional computational fluid dynamics (3D CFD) modeling. A one-dimensional pump model is developed to account for contactless bubble-bubble interactions, and the accuracy of the developed one-dimensional model is assessed via commercial volume of fluid CFD software, FLOW-3D. The FLOW-3D CFD model is validated against experimental bubble dynamics images as well as experimental pump data. Pre-collapse and post-collapse bubble and flow dynamics for two resistors in a channel have been successfully explained by the modified one-dimensional model. The net pumping effect design space is characterized as a function of resistor placement and firing time delay. The one-dimensional model accurately predicts cumulative flow for simultaneous resistor firing with inner-channel resistor placements (0.2L < x < 0.8L where L is the channel length) as well as delayed resistor firing with inner-channel resistor placements when the time delay is greater than the time required for the vapor bubble to fill the channel cross-section. In general, one-dimensional model accuracy suffers at near-reservoir resistor placements and short time delays which we propose is a result of 3D bubble-reservoir interactions and transverse bubble growth interactions respectively that are not captured by the one-dimensional model. We find that the one- dimensional model accuracy improves for smaller channel heights. We envision the developed one-dimensional model as a first-order rapid design tool for inertial pump based microfluidic systems operating in the contactless bubble-bubble interaction non-linear regime.
@article{doi:10.1063/5.0041924, year = {2021}, publisher = {American Institute of Physics}, author = {Hayes, B. and Whiting, G. L. and MacCurdy, R.}, title = {Modeling of contactless bubble–bubble interactions in microchannels with integrated inertial pumps}, journal = {Physics of Fluids}, volume = {33}, number = {4}, pages = {042002}, doi = {10.1063/5.0041924}, url = { https://doi.org/10.1063/5.0041924}, eprint = { https://doi.org/10.1063/5.0041924}, }

2020

A Fabrication Free, 3D Printed, Multi-Material, Self-Sensing Soft Actuator

Travis Hainsworth, Lawrence Smith, Sebastian Alexander, and Robert MacCurdy

IEEE Robotics and Automation Letters, Jun 2020

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Soft robotics offers a range of attractive features relative to traditional rigid robots, including rapid customiza- tion, inherently safer human-robot interactions, and continuous passive dynamics that enable morphological computation. Here we present an actuator with an integrated print-in-place strain sensor which is produced entirely via multi-material additive manufacturing and requires no post processing or manual fabrication steps. One natural application of this technology is the end effector of robotic arms; incorporating deformable actuators into a gripping mechanism allows for the safe integration of robotic assistance in human-occupied settings. While numerous soft robot actuators have been implemented without feedback, force sensing and proprioception are valuable signals to leverage in extending the capabilities of these systems. Prior approaches to integrating sensors into soft robot components have relied on manual processes, or specialized fabrication tools. Our work shows a novel method for automatically manufacturing soft pneumatically-driven actuators with embedded sensors through readily available 3D printing tools with no human fabrication required. Automatically manufacturing these sensor-actuator sys- tems enables more complex, capable, and integrate-able designs, because the labor of assembly is eliminated; actuator-sensor designs that would be tedious or impossible to manufacture become tractable with our approach.
@article{hainsworth2020fabrication, year = {2020}, publisher = {IEEE}, author = {Hainsworth, Travis and Smith, Lawrence and Alexander, Sebastian and MacCurdy, Robert}, journal = {IEEE Robotics and Automation Letters}, volume = {5}, title = {A Fabrication Free, 3D Printed, Multi-Material, Self-Sensing Soft Actuator}, number = {3}, pages = {4118--4125}, }
The surprising creativity of digital evolution: A collection of anecdotes from the evolutionary computation and artificial life research communities

Joel Lehman, Jeff Clune, Dusan Misevic, Christoph Adami, Lee Altenberg, and 6 more authors

Artificial Life, Jun 2020

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Evolution provides a creative fount of complex and subtle adaptations that often surprise the scientists who discover them. However, the creativity of evolution is not limited to the natural world: artificial organisms evolving in computational environments have also elicited surprise and wonder from the researchers studying them. The process of evolution is an algorithmic process that transcends the substrate in which it occurs. Indeed, many researchers in the field of digital evolution can provide examples of how their evolving algorithms and organisms have creatively subverted their expectations or intentions, exposed unrecognized bugs in their code, produced unexpectedly adaptations, or engaged in behaviors and outcomes uncannily convergent with ones found in nature. Such stories routinely reveal surprise and creativity by evolution in these digital worlds, but they rarely fit into the standard scientific narrative. Instead they are often treated as mere obstacles to be overcome, rather than results that warrant study in their own right. Bugs are fixed, experiments are refocused, and one-off surprises are collapsed into a single data point. The stories themselves are traded among researchers through oral tradition, but that mode of information transmission is inefficient and prone to error and outright loss. Moreover, the fact that these stories tend to be shared only among practitioners means that many natural scientists do not realize how interesting and lifelike digital organisms are and how natural their evolution can be. To our knowledge, no collection of such anecdotes has been published before. This paper is the crowd-sourced product of researchers in the fields of artificial life and evolutionary computation who have provided first-hand accounts of such cases. It thus serves as a written, fact-checked collection of scientifically important and even entertaining stories. In doing so we also present here substantial evidence that the existence and importance of evolutionary surprises extends beyond the natural world, and may indeed be a universal property of all complex evolving systems.
@article{lehman2020surprising, year = {2020}, publisher = {MIT Press}, title = {The surprising creativity of digital evolution: A collection of anecdotes from the evolutionary computation and artificial life research communities}, author = {Lehman, Joel and Clune, Jeff and Misevic, Dusan and Adami, Christoph and Altenberg, Lee and Beaulieu, Julie and Bentley, Peter J and Bernard, Samuel and Beslon, Guillaume and Bryson, David M and others}, journal = {Artificial Life}, volume = {26}, number = {2}, pages = {274--306}, }

2018

Automated Wildlife Radio Tracking

Robert B MacCurdy, Allert I Bijleveld, Richard M Gabrielson, and Kathryn A Cortopassi

Handbook of Position Location: Theory, Practice, and Advances, Second Edition, Jun 2018

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Radio direction-finding techniques have been widely employed by the wildlife track- ing community because they offer powerful, flexible tools for monitoring animal movements and behavior. Reductions in the size and power consumption of GPS chipsets have recently allowed GPS location-finding techniques to also be applied to wildlife monitoring. Despite their successes, these approaches still have signifi- cant shortcomings, primarily due to the energy constraints imposed by the allowable mass of the electrochemical battery that can be carried by the animal. This require- ment causes tag lifetimes to be shorter than desired. Attaching a tracking collar is a risky procedure for all participants, and maximizing the tag service intervals is extremely important. This is true even for large animals, which can carry significant tag mass without behavior disruptions. Therefore, disturbances to the animal (which are primarily driven by tag energy consumption), followed closely by cost are the primary design requirements. These requirements motivate a new tracking system, based on time-of-arrival (TOA) measurements. This system is similar in many respects to GPS; the primary difference is that in this system the mobile asset to be tracked emits, rather than receives, signals. Although transmitting a radiofrequency signal is often the most power-intensive operation for a tag, this choice yields a system with average tag energy requirements that are lower than any current radio-tracking method. Though this chapter focuses on the application of this technology to monitor- ing animal movements, the same set of design criteria apply to generic asset tracking, and we believe that there is a universal need for a local terrestrial tracking system that offers precise positioning with tiny, cheap, long-lived tracking tags.
@article{maccurdy2018automated, year = {2018}, publisher = {Wiley Online Library}, title = {Automated Wildlife Radio Tracking}, author = {MacCurdy, Robert B and Bijleveld, Allert I and Gabrielson, Richard M and Cortopassi, Kathryn A}, journal = {Handbook of Position Location: Theory, Practice, and Advances, Second Edition}, pages = {1219--1261}, }
Handedness in shearing auxetics creates rigid and compliant structures

Jeffrey Ian Lipton, Robert MacCurdy, Zachary Manchester, Lillian Chin, Daniel Cellucci, and 1 more author

Science, Jun 2018

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In nature, repeated base units produce handed structures that selectively bond to make rigid or compliant materials. Auxetic tilings are scale-independent frameworks made from repeated unit cells that expand under tension. We discovered how to produce handedness in auxetic unit cells that shear as they expand by changing the symmetries and alignments of auxetic tilings. Using the symmetry and alignment rules that we developed, we made handed shearing auxetics that tile planes, cylinders, and spheres. By compositing the handed shearing auxetics in a manner inspired by keratin and collagen, we produce both compliant structures that expand while twisting and deployable structures that can rigidly lock. This work opens up new possibilities in designing chemical frameworks, medical devices like stents, robotic systems, and deployable engineering structures.
@article{Lipton2018, year = {2018}, publisher = {American Association for the Advancement of Science}, author = {Lipton, Jeffrey Ian and MacCurdy, Robert and Manchester, Zachary and Chin, Lillian and Cellucci, Daniel and Rus, Daniela}, title = {Handedness in shearing auxetics creates rigid and compliant structures}, journal = {Science}, volume = {360}, pages = {632--635}, number = {6389}, doi = {10.1126/science.aar4586}, eprint = {http://science.sciencemag.org/content/360/6389/632.full.pdf}, issn = {0036-8075}, owner = {RobM}, }
Compliant Electric Actuators Based on Handed Shearing Auxetics

In Proceedings of IEEE-RAS International Conference on Soft Robotics (RoboSoft), Jun 2018

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In this paper, we explore a new class of electric motor-driven compliant actuators based on handed shearing auxetic cylinders. This technique combines the benefits of compliant bodies from soft robotic actuators with the simplicity of direct coupling to electric motors. We demonstrate the effectiveness of this technique by creating linear actuators, a four degree-of-freedom robotic platform, and a soft robotic gripper. We compare the soft robotic gripper against a state of the art pneumatic soft gripper, finding similar grasping performance in a significantly smaller and more energy-efficient package.
@inproceedings{LillianChin2018, year = {2018}, publisher = {IEEE}, author = {}, title = {Compliant Electric Actuators Based on Handed Shearing Auxetics}, booktitle = {Proceedings of IEEE-RAS International Conference on Soft Robotics (RoboSoft)}, journal = {IEEE-RAS International Conference on Soft Robotics (RoboSoft)}, }
Exploration of underwater life with an acoustically controlled soft robotic fish

Robert K. Katzschmann, Joseph DelPreto, Robert MacCurdy, and Daniela Rus

Science Robotics, Jun 2018

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Closeup exploration of underwater life requires new forms of interaction, using biomimetic creatures that are capable of agile swimming maneuvers, equipped with cameras, and supported by remote human operation. Cur- rent robotic prototypes do not provide adequate platforms for studying marine life in their natural habitats. This work presents the design, fabrication, control, and oceanic testing of a soft robotic fish that can swim in three di- mensions to continuously record the aquatic life it is following or engaging. Using a miniaturized acoustic com- munication module, a diver can direct the fish by sending commands such as speed, turning angle, and dynamic vertical diving. This work builds on previous generations of robotic fish that were restricted to one plane in shallow water and lacked remote control. Experimental results gathered from tests along coral reefs in the Pacific Ocean show that the robotic fish can successfully navigate around aquatic life at depths ranging from 0 to 18 meters. Furthermore, our robotic fish exhibits a lifelike undulating tail motion enabled by a soft robotic actuator design that can potentially facilitate a more natural integration into the ocean environment. We believe that our study advances beyond what is currently achievable using traditional thruster-based and tethered autonomous under- water vehicles, demonstrating methods that can be used in the future for studying the interactions of aquatic life and ocean dynamics.
@article{Katzschmanneaar3449, year = {2018}, publisher = {Science Robotics}, author = {Katzschmann, Robert K. and DelPreto, Joseph and MacCurdy, Robert and Rus, Daniela}, title = {Exploration of underwater life with an acoustically controlled soft robotic fish}, journal = {Science Robotics}, volume = {3}, number = {16}, doi = {10.1126/scirobotics.aar3449}, eprint = {http://robotics.sciencemag.org/content/3/16/eaar3449.full.pdf}, file = {:C\:\\Dropbox (Personal)\\Junction\\Documents\\Refs & Journal Articles\\MyPubs\\2018_Katzschmann-Exploration of underwater life with an acoustically controlled soft robot fish.pdf:PDF}, owner = {RobM}, }

2017

Trouble on takeoff: Crude oil on feathers reduces escape performance of shorebirds

Jun 2017

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The ability to takeoff quickly and accelerate away from predators is crucial to bird survival. Crude oil can disrupt the fine structure and function of feathers, and here we tested for the first time how small amounts of oil on the trailing edges of the wings and tail of Western sandpipers (Calidris mauri) affected takeoff flight performance. In oiled birds, the distance travelled during the first 0.4 s after takeoff was reduced by 29%, and takeoff angle was decreased by 10° compared to unoiled birds. Three-axis accelerometry indicated that oiled sandpipers produced less mechanical power output per wingbeat during the initial phase of flight. Slower and lower takeoff would make oiled birds more likely to be targeted and captured by predators, reducing survival and facilitating the exposure of predators to oil. Whereas the direct mortality of heavily-oiled birds is often obvious and can be quantified, our results show that there are significant sub-lethal effects of small amounts crude oil on feathers, which must be considered in natural resource injury assessments for birds.
@article{maccurdy2017, year = {2017}, publisher = {American Association for the Advancement of Science}, title = {Trouble on takeoff: Crude oil on feathers reduces escape performance of shorebirds}, author = {}, }
1D Printing of Recyclable Robots

D. Cellucci, R. MacCurdy, H. Lipson, and S. Risi

IEEE Robotics and Automation Letters, Jun 2017

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Recent advances in 3D printing are revolutionizing manufacturing, enabling the fabrication of structures with un- precedented complexity and functionality. Yet biological systems are able to fabricate systems with far greater complexity using a process that involves assembling and folding a linear string. Here, we demonstrate a 1D printing system that uses an approach in- spired by the ribosome to fabricate a variety of specialized robotic automata from a single string of source material. This proof-of- concept system involves both a novel manufacturing platform that configures the source material using folding and a computational optimization tool that allows designs to be produced from the specification of high-level goals. We show that our 1D printing system is able to produce three distinct robots from the same source material, each of which is capable of accomplishing a specialized locomotion task. Moreover, we demonstrate the ability of the printer to use recycled material to produce new designs, enabling an autonomous manufacturing ecosystem capable of repurposing previous iterations to accomplish new tasks.
@article{Risi2017_ribo, year = {2017}, publisher = {IEEE}, author = {Cellucci, D. and MacCurdy, R. and Lipson, H. and Risi, S.}, title = {1D Printing of Recyclable Robots}, journal = {IEEE Robotics and Automation Letters}, volume = {PP}, pages = {1-1}, number = {99}, doi = {10.1109/LRA.2017.2716418}, issn = {2377-3766}, keywords = {AI-Based Methods;Assembly;Mechanism Design;Neural and Fuzzy Control}, }

2016

Printable Programmable Viscoelastic Materials for Robots

Robert MacCurdy, Jeffery Lipton, Shuguang Li, and Daniela Rus

Jun 2016

IROS (submitted)

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Impact protection and vibration isolation are an important component of the mobile robot designer’s toolkit; however, current damping materials are available only in bulk or molded form, requiring manual fabrication steps and restricting material property control. In this paper we demon- strate a new method for 3D printing viscoelastic materials with specified material properties. This method allows arbitrary net-shape material geometries to be rapidly fabricated and enables continuously varying material properties throughout the finished part. This new ability allows robot designers to tailor the properties of viscoelastic damping materials in order to reduce impact forces and isolate vibrations. We present a case study for using this material to create jumping robots with programmed levels of bouncing.
@conference{maccurdy_visco, year = {2016}, publisher = {IEEE}, author = {MacCurdy, Robert and Lipton, Jeffery and Li, Shuguang and Rus, Daniela}, title = {Printable Programmable Viscoelastic Materials for Robots}, booktitle = {2016 2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)}, note = {IROS (submitted)}, }
Printable hydraulics: A method for fabricating robots by 3D co-printing solids and liquids

R. MacCurdy, R. Katzschmann, Youbin Kim, and D. Rus

Jun 2016

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This paper introduces a novel technique for fabri- cating functional robots using 3D printers. Simultaneously de- positing photopolymers and a non-curing liquid allows complex, pre-filled fluidic channels to be fabricated. This new printing capability enables complex hydraulically actuated robots and robotic components to be automatically built, with no assem- bly required. The technique is showcased by printing linear bellows actuators, gear pumps, soft grippers and a hexapod robot, using a commercially-available 3D printer. We detail the steps required to modify the printer and describe the design constraints imposed by this new fabrication approach.
@conference{maccurdyprintedhydraulics, year = {2016}, publisher = {IEEE}, author = {MacCurdy, R. and Katzschmann, R. and Kim, Youbin and Rus, D.}, title = {Printable hydraulics: A method for fabricating robots by 3D co-printing solids and liquids}, booktitle = {2016 IEEE International Conference on Robotics and Automation (ICRA)}, pages = {3878-3885}, doi = {10.1109/ICRA.2016.7487576}, }
Understanding spatial distributions: Negative density-dependence in prey causes predators to trade-off prey quantity with quality

Allert I. Bijleveld, Robert B. MacCurdy, Ying Chi Chan, Emma Penning, Rich M. Gabrielson, and 9 more authors

Proc. R. Soc. B, Jun 2016

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Negative density-dependence is generally studied within a single trophic level, thereby neglecting its effect on higher trophic levels. The ‘functional response’ couples a predator’s intake rate to prey density. Most widespread is a type II functional response, where intake rate increases asymptotically with prey den- sity; this predicts the highest predator densities at the highest prey densities. In one of the most stringent tests of this generality to date, we measured density and quality of bivalve prey (edible cockles Cerastoderma edule) across 50 km2 of mudflat, and simultaneously, with a novel time-of-arrival methodology, tracked their avian predators (red knots Calidris canutus). Because of negative density-dependence in the individual quality of cockles, the predicted energy intake rates of red knots declined at high prey densities (a type IV, rather than a type II functional response). Resource-selection modelling revealed that red knots indeed selected areas of intermediate cockle densities where energy intake rates were maximized given their phenotype-specific digestive constraints (as indicated by gizzard mass). Because negative density- dependence is common, we question the current consensus and suggest that predators commonly maximize their energy intake rates at intermediate prey densities. Prey density alone may thus poorly predict intake rates, carrying capacity and spatial distributions of predators.
@article{allertbijleveld2015, year = {2016}, publisher = {Royal Society}, author = {Bijleveld, Allert I. and MacCurdy, Robert B. and Chan, Ying Chi and Penning, Emma and Gabrielson, Rich M. and Cluderay, John and Spaulding, Eric L. and Dekinga, Anne and Holthuijsen, Sander and ten Horn, Job and Brugge, Maarten and van Gils, Jan A. and Winkler, David W. and Piersma, Theunis}, title = {Understanding spatial distributions: Negative density-dependence in prey causes predators to trade-off prey quantity with quality}, journal = {Proc. R. Soc. B}, volume = {283}, number = {1828}, pages = {20151557}, url = {http://dx.doi.org/10.1098/rspb.2015.1557}, doi = {10.1098/rspb.2015.1557}, }

2015

A Compact Acoustic Communication Module for Remote Control Underwater

Joseph DelPreto, Robert Katzschmann, Robert MacCurdy, and Daniela Rus

In Proceedings of the 10th International Conference on Underwater Networks & Systems, Jun 2015

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This paper describes an end-to-end compact acoustic com- munication system designed for easy integration into re- motely controlled underwater operations. The system sup- ports up to 2048 commands that are encoded as 16 bit words. We present the design, hardware, and supporting algorithms for this system. A pulse-based FSK modulation scheme is presented, along with a method of demodulation requiring minimal processing power that leverages the Goertzel algo- rithm and dynamic peak detection. We packaged the system together with an intuitive user interface for remotely control- ling an autonomous underwater vehicle. We evaluated this system in the pool and in the open ocean. We present the communication data collected during experiments using the system to control an underwater robot.
@inproceedings{delpreto2015compact, year = {2015}, publisher = {WUWNet '15: Proceedings of the 10th International Conference on Underwater Networks & Systems}, author = {DelPreto, Joseph and Katzschmann, Robert and MacCurdy, Robert and Rus, Daniela}, title = {A Compact Acoustic Communication Module for Remote Control Underwater}, booktitle = {Proceedings of the 10th International Conference on Underwater Networks & Systems}, pages = {13}, }
System and Methods for Additive Manufacturing of Electromechanical Assemblies

Robert MacCurdy, and Hod Lipson

Jun 2015

PCT/US2015/026848

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A hybrid additive manufacturing approach that incorporates three-dimensional (3D) printing and placement of modules selected from a library of modules to fabricate an electromechanical assembly. By virtue of fabrication of the electromechanical assembly, mechanical properties and electrical properties of the assembly are created. The invention overcomes the material and process limitations of current printable electronics approaches, enabling complete, complex electromechanical assemblies to be fabricated.
@misc{2015_maccurdy_hybprint_pat, year = {2015}, publisher = {PCT Patent Application}, author = {MacCurdy, Robert and Lipson, Hod}, title = {System and Methods for Additive Manufacturing of Electromechanical Assemblies}, howpublished = {PCT Patent Application}, note = {PCT/US2015/026848}, }
The case for energy harvesting on wildlife in flight

Michael W Shafer, Robert MacCurdy, J Ryan Shipley, David Winkler, Christopher G Guglielmo, and 1 more author

Smart Materials and Structures, Jun 2015

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The confluence of advancements in microelectronic components and vibrational energy harvesting has opened the possibility of remote sensor units powered solely from the motion of their hosts. There are numerous applications of such systems, including the development of modern wildlife tracking/data-logging devices. These ‘bio-logging’ devices are typically mass- constrained because they must be carried by an animal. Thus, they have historically traded scientific capability for operational longevity due to restrictions on battery size. Recently, the precipitous decrease in the power requirements of microelectronics has been accompanied by advancements in the area of piezoelectric vibrational energy harvesting. These energy harvesting devices are now capable of powering the type of microelectronic circuits used in bio-logging devices. In this paper we consider the feasibility of employing these vibrational energy harvesters on flying vertebrates for the purpose of powering a bio-logging device. We show that the excess energy available from birds and bats could be harvested without adversely affecting their overall energy budget. We then present acceleration measurements taken on flying birds in a flight tunnel to understand modulation of flapping frequency during steady flight. Finally, we use a recently developed method of estimating the maximum power output from a piezoelectric energy harvester to determine the amount of power that could be practically harvested from a flying bird. The results of this analysis show that the average power output of a piezoelectric energy harvester mounted to a bird or bat could produce more than enough power to run a bio- logging device. We compare the power harvesting capabilities to the energy requirements of an example system and conclude that vibrational energy harvesting on flying birds and bats is viable and warrants further study, including testing.
@article{shafer2015case, year = {2015}, publisher = {IOP Publishing}, author = {Shafer, Michael W and MacCurdy, Robert and Shipley, J Ryan and Winkler, David and Guglielmo, Christopher G and Garcia, Ephrahim}, title = {The case for energy harvesting on wildlife in flight}, journal = {Smart Materials and Structures}, volume = {24}, number = {2}, pages = {025031}, }

2014

Hybrid printing of photopolymers and electromechanical assemblies

R MacCurdy, and H Lipson

In Proceedings of the 25th Solid Freeform Fabrication Symposium, Jun 2014

Bib

@inproceedings{MacCurdy2014a,
  year = {2014},
  publisher = {IOP Publishing},
  author = {MacCurdy, R and Lipson, H},
  title = {Hybrid printing of photopolymers and electromechanical assemblies},
  booktitle = {Proceedings of the 25th Solid Freeform Fabrication Symposium}
}

Unshackling evolution: evolving soft robots with multiple materials and a powerful generative encoding

Nick Cheney, Robert MacCurdy, Jeff Clune, and Hod Lipson

ACM SIGEVOlution, Jun 2014

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In 1994, Karl Sims’ evolved virtual creatures showed the potential of evolutionary algorithms to produce natural, complex morphologies and behaviors [30]. One might assume that nearly 20 years of improvements in computational speed and evolutionary algorithms would produce far more impressive organisms, yet the creatures evolved in the field of artificial life today are not obviously more complex, natural, or intelligent. Fig. 2 demonstrates an example of similar complexity in robots evolved 17 years apart.
@article{cheney2014unshackling, year = {2014}, author = {Cheney, Nick and MacCurdy, Robert and Clune, Jeff and Lipson, Hod}, title = {Unshackling evolution: evolving soft robots with multiple materials and a powerful generative encoding}, journal = {ACM SIGEVOlution}, publisher = {ACM}, volume = {7}, number = {1}, pages = {11--23}, }
Bitblox: A Printable Digital Material for Electromechanical Machines

Robert MacCurdy, Anthony McNicoll, and Hod Lipson

International Journal of Robotics Research, Jun 2014

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As additive manufacturing of mechanical parts gains broad acceptance, efforts to embed electronic or electromechanical components in these parts are intensifying. We discuss recent work in printable electronics and introduce an alternative, which we call Bitblox. Bitblox are small, modular, interconnecting blocks that embed simple electromechanical connectivity and functionality. Not all blocks are identical; instead the unique combinations and positions of Bitblox within an assembly determine the mechanical and electrical properties of the assembly. We describe the design details of Bitblox, compare them to similar materials, and demonstrate their use in a working three-dimensional printer through several examples.
@article{MacCurdy2014, year = {2014}, publisher = {The International Journal of Robotics Research}, author = {MacCurdy, Robert and McNicoll, Anthony and Lipson, Hod}, title = {Bitblox: A Printable Digital Material for Electromechanical Machines}, journal = {International Journal of Robotics Research}, volume = {33}, number = {10}, pages = {1342-1360}, doi = {10.1177/0278364914532149}, }

Fine-scale measurements of individual movements within bird flocks: the principles and three applications of TOA tracking

Theunis Piersma, Robert B MacCurdy, Rich M Gabrielson, John Cluderay, Anne Dekinga, and 6 more authors

Limosa, Jun 2014

Bib PDF

@article{piersma2014,
  year = {2014},
  publisher = {Limosa},
  author = {Piersma, Theunis and MacCurdy, Robert B and Gabrielson, Rich M and Cluderay, John and Dekinga, Anne and Spaulding, Eric L and Oudman, Thomas and Onrust, Jeroen and van Gils, Jan A and Winkler, David W and Bijleveld, Allert I.},
  title = {Fine-scale measurements of individual movements within bird flocks: the principles and three applications of TOA tracking},
  journal = {Limosa},
  volume = {87},
  pages = {156-167},
}

2013

Digitally controlled tracking device and related methods

Robert MacCurdy, Steve Powell, Richard Gabrielson, and David Winkler

Jun 2013

U.S. Provisional Patent No. 61/894543

Bib PDF

@misc{maccurdy2013,
  year = {2013},
  publisher = {Limosa},
  author = {MacCurdy, Robert and Powell, Steve and Gabrielson, Richard and Winkler, David},
  title = {Digitally controlled tracking device and related methods},
  note = {U.S. Provisional Patent No. 61/894543},
}

Testing of vibrational energy harvesting on flying birds

M. W. Shafer, R. MacCurdy, and E. Garcia

In In Proceedings of ASME Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS), Jun 2013

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Discrete animal-mounted sensors and tags have a wide range of potential applications for researching wild animals and their environments. The devices could be used to monitor location, metabolic output, or used as environmental monitoring sentinels. These applications are made possible by recent decreases in the size, mass, and power consumption of modern microelectronics. Despite these performance increases, for extended deployments these systems need to generate power in-situ. In this work, we explore a device that was recently deployed to test the concept of piezoelectric energy harvesting on flying birds. We explain the development of the device and introduce test results conducted on flying pigeons (Columba livia). The testing device consisted of a miniature data acquisition system, piezoelectric energy har- vester, and actuator system. The output of the energy harvester was monitored by a microcontroller and recorded throughout the flight. The energy harvester included a wireless receiver, bat- tery and linear servo. By remotely actuating the linear servo, we were able to arrest the energy harvester for portions of the flight. In doing so, we will be able to compare flight accelerations of a bird with a simple proof mass and with a dynamic mass without having to stop the flight of the bird. The comparison of these two cases allows for the assessment of the feasibility of employing vibrational energy harvesting on a flying bird. We present the initial results of this testing with regard to the harvested power and the in-flight acceleration profiles.
@inproceedings{Shafer2013, year = {2013}, publisher = {ASME 2013 Conference on Smart Materials}, author = {Shafer, M. W. and MacCurdy, R. and Garcia, E.}, title = {Testing of vibrational energy harvesting on flying birds}, booktitle = {In Proceedings of ASME Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS)}, }
Unshackling Evolution: Evolving Soft Robots with Multiple Materials and a Powerful Generative Encoding

Nick Cheney, Robert MacCurdy, Jeff Clune, and Hod Lipson

In Proceedings of the15th annual conference on genetic and evolutionary computation (GECCO), Jun 2013

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In 1994 Karl Sims showed that computational evolution can produce interesting morphologies that resemble natural or- ganisms. Despite nearly two decades of work since, evolved morphologies are not obviously more complex or natural, and the field seems to have hit a complexity ceiling. One hypothesis for the lack of increased complexity is that most work, including Sims’, evolves morphologies composed of rigid elements, such as solid cubes and cylinders, limiting the design space. A second hypothesis is that the encod- ings of previous work have been overly regular, not allow- ing complex regularities with variation. Here we test both hypotheses by evolving soft robots with multiple materials and a powerful generative encoding called a compositional pattern-producing network (CPPN). Robots are selected for locomotion speed. We find that CPPNs evolve faster robots than a direct encoding and that the CPPN morphologies appear more natural. We also find that locomotion per- formance increases as more materials are added, that di- versity of form and behavior can be increased with differ- ent cost functions without stifling performance, and that organisms can be evolved at different levels of resolution. These findings suggest the ability of generative soft-voxel systems to scale towards evolving a large diversity of com- plex, natural, multi-material creatures. Our results suggest that future work that combines the evolution of CPPN- encoded soft, multi-material robots with modern diversity- encouraging techniques could finally enable the creation of creatures far more complex and interesting than those pro- duced by Sims nearly twenty years ago.
@inproceedings{cheney2013, year = {2013}, publisher = {ACM SIGEVOlution, Volume 7, Issue 1}, author = {Cheney, Nick and MacCurdy, Robert and Clune, Jeff and Lipson, Hod}, title = {Unshackling Evolution: Evolving Soft Robots with Multiple Materials and a Powerful Generative Encoding}, booktitle = {Proceedings of the15th annual conference on genetic and evolutionary computation (GECCO)}, }
Advances in tracking small migratory birds: a technical review of light-level geolocation

Eli S Bridge, Jeffrey F Kelly, Andrea Contina, Richard M Gabrielson, Robert B MacCurdy, and 1 more author

Journal of Field Ornithology, Jun 2013

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Light-level geolocation data loggers, or geologgers, have recently been miniaturized to the extent that they can be deployed on small songbirds, allowing us to determine many previously unknown migration routes, breeding locations, and wintering sites. Use of geologgers on small birds has great potential to help address major research and conservation questions, but the method is not without its shortcomings. Among these shortcomings are the need to recapture birds after they have carried a device throughout a migration cycle and the potential for the devices to affect survival and behavior. We examined return rates of birds with geologgers in published and unpublished studies and found no evidence of a general negative effect of geologgers on survival, although there were a few individual studies where such an effect was evident. From these same studies, we found that most currently used harness materials are equivalent in terms of failure rates, and the most reliable geologgers are those made by the British Antarctic Survey (although these were also the largest geologgers used in the studies we examined). With regard to analysis methods, we believe there is much room for improvement. Use of online archiving of both data and analysis parameters would greatly improve the repeatability and transparency of geologger research.
@article{Bridge2013, year = {2013}, publisher = {Wiley Online Library}, author = {Bridge, Eli S and Kelly, Jeffrey F and Contina, Andrea and Gabrielson, Richard M and MacCurdy, Robert B and Winkler, David W}, title = {Advances in tracking small migratory birds: a technical review of light-level geolocation}, journal = {Journal of Field Ornithology}, volume = {84}, number = {2}, pages = {121--137}, }

2012

Fab@ home model 3: a more robust, cost effective and accessible open hardware fabrication platform

Jeffrey Lipton, Robert MacCurdy, Matt Boban, Nick Chartrain, Lawrence Withers III, and 7 more authors

In Proceedings of the Twenty Third Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference, August 6-8, 2012, Austin, Texas, USA., Jun 2012

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Solid Freeform Fabrication is transitioning from an industrial process and research endeavor towards a ubiquitous technology in the lives of every designer and innovator. In order to speed this transition Fab@Home Model 3 was created with the goal of expanding the user base of SFF technology by lowering the skill and price barriers to entry while enabling technology developers to leverage their core competencies more efficiently. The result is a device, which is modular with respect to tool heads, fabrication processes, and electronics controls, costs under $1000, and requires only a simple tool set to assemble.
@inproceedings{Lipton2012, year = {2012}, publisher = {University of Texas at Austin}, author = {Lipton, Jeffrey and MacCurdy, Robert and Boban, Matt and Chartrain, Nick and Withers III, Lawrence and Gangjee, Natasha and Nagai, Alex and Cohen, Jeremy and Liu, Karina Sobhani Jimmy and Qudsi, Hana and Kaufman, Jonathan and Lipson, Hod}, title = {Fab@ home model 3: a more robust, cost effective and accessible open hardware fabrication platform}, booktitle = {Proceedings of the Twenty Third Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference, August 6-8, 2012, Austin, Texas, USA.}, }

Automated Wildlife Radio Tracking

Robert B MacCurdy, Richard M Gabrielson, and Kathryn A Cortopassi

Jun 2012

Bib PDF

@inbook{maccurdy2012automated,
  year = {2012},
  publisher = {John Wiley & Sons, Inc.},
  author = {MacCurdy, Robert B and Gabrielson, Richard M and Cortopassi, Kathryn A},
  editor = {Zekavat, Seyed A. and Buehrer, R. Michael.},
  title = {Automated Wildlife Radio Tracking},
  journal = {Handbook of Position Location: Theory, Practice, and Advances},
  pages = {1129--1167},
}

Harvestable vibrational energy from an avian source: theoretical predictions vs. measured values

Michael W Shafer, Robert MacCurdy, Ephrahim Garcia, and David Winkler

In SPIE Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring, Jun 2012

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For many reasons, it would be beneficial to have the capability of powering a wildlife tag over the course of multiple migratory seasons. Such an energy harvesting system would allow for more data collection and eliminate the need to replace depleted batteries. In this work, we investigate energy harvesting on birds and focus on vibrational energy harvesting. We review a method of predicting the amount of power that can be safely harvested from the birds such that the effect on their longterm survivability is not compromised. After showing that the safely harvestable power is significant in comparison to the circuits used in avian tags, we present testing results for the flight accelerations of two species of birds. Using these measured values, we then design harvesters that matched the flight acceleration frequency and are sufficiently low mass to be carried by the birds.
@inproceedings{Shafer2012, year = {2012}, publisher = {Spie Digital Library}, author = {Shafer, Michael W and MacCurdy, Robert and Garcia, Ephrahim and Winkler, David}, title = {Harvestable vibrational energy from an avian source: theoretical predictions vs. measured values}, booktitle = {SPIE Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring}, pages = {834103--834103}, url = {http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1313102}, }
Constructing controllers for physical multilegged robots using the enso neuroevolution approach

Vinod K Valsalam, Jonathan Hiller, Robert MacCurdy, Hod Lipson, and Risto Miikkulainen

Evolutionary Intelligence, Jun 2012

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Evolving controllers for multilegged robots in simulation is convenient and flexible, making it possible to prototype ideas rapidly. However, transferring the resulting controllers to physical robots is challenging because it is difficult to simulate real-world complexities with sufficient accuracy. This paper bridges this gap by utilizing the Evolution of Network Symmetry and mOdularity (ENSO) approach to evolve modular neural network controllers that are robust to discrepancies between simulation and reality. This approach was evaluated by building a physical quadruped robot and by evolving controllers for it in simulation. An approximate model of the robot and its environment was built in a physical simulation and uncertainties in the real world were modeled as noise. The resulting controllers produced well-synchronized trot gaits when they were transferred to the physical robot, even on different walking surfaces. In contrast to a hand-designed PID controller, the evolved controllers also generalized well to changes in experimental conditions such as loss of voltage and were more robust against faults such as loss of a leg, making them strong candidates for real-world applications.
@article{Valsalam2012, year = {2012}, publisher = {Springer}, author = {Valsalam, Vinod K and Hiller, Jonathan and MacCurdy, Robert and Lipson, Hod and Miikkulainen, Risto}, title = {Constructing controllers for physical multilegged robots using the enso neuroevolution approach}, journal = {Evolutionary Intelligence}, volume = {5}, number = {1}, pages = {45--56}, url = {http://link.springer.com/article/10.1007/s12065-011-0067-y}, }

2011

Three-dimensional root phenotyping with a novel imaging and software platform

Randy T Clark, Robert B MacCurdy, Janelle K Jung, Jon E Shaff, Susan R McCouch, and 2 more authors

Plant Physiology, Jun 2011

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A novel imaging and software platform was developed for the high-throughput phenotyping of three-dimensional root traits during seedling development. To demonstrate the platform’s capacity, plants of two rice (Oryza sativa) genotypes, Azucena and IR64, were grown in a transparent gellan gum system and imaged daily for 10 d. Rotational image sequences consisting of 40 two-dimensional images were captured using an optically corrected digital imaging system. Three-dimensional root reconstructions were generated and analyzed using a custom-designed software, RootReader3D. Using the automated and interactive capabilities of RootReader3D, five rice root types were classified and 27 phenotypic root traits were measured to characterize these two genotypes. Where possible, measurements from the three-dimensional platform were validated and were highly correlated with conventional two-dimensional measurements. When comparing gellan gum-grown plants with those grown under hydroponic and sand culture, significant differences were detected in morphological root traits (P < 0.05). This highly flexible platform provides the capacity to measure root traits with a high degree of spatial and temporal resolution and will facilitate novel investigations into the development of entire root systems or selected components of root systems. In combination with the extensive genetic resources that are now available, this platform will be a powerful resource to further explore the molecular and genetic determinants of root system architecture.
@article{Clark2011, year = {2011}, author = {Clark, Randy T and MacCurdy, Robert B and Jung, Janelle K and Shaff, Jon E and McCouch, Susan R and Aneshansley, Daniel J and Kochian, Leon V}, title = {Three-dimensional root phenotyping with a novel imaging and software platform}, journal = {Plant Physiology}, publisher = {Am Soc Plant Biol}, volume = {156}, number = {2}, pages = {455--465}, url = {http://www.plantphysiol.org/content/156/2/455.short}, }
Electrical power generation from insect flight

Timothy Reissman, Robert B MacCurdy, and Ephrahim Garcia

In SPIE Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring, Jun 2011

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This article presents an implementation of a miniature energy harvester (weighing 0.292 grams) on an insect (hawkmoth Manduca sexta) in un-tethered flight. The harvester utilizes a piezoelectric transducer which converts the vibratory motion induced by the insect’s flight into electrical power (generating up to 59 μWRMS). By attaching a low-power management circuit (weighing 0.200 grams) to the energy harvester and accumulating the converted energy onboard the flying insect, we are able to visually demonstrate pulsed power delivery (averaging 196 mW) by intermittently flashing a light emitting diode. This self-recharging system offers biologists a new means for powering onboard electronics used to study small flying animals. Using this approach, the lifetime of the electronics would be limited only by the lifetime of the individuals, a vast improvement over current methods.
@inproceedings{reissman2011electrical, year = {2011}, author = {Reissman, Timothy and MacCurdy, Robert B and Garcia, Ephrahim}, title = {Electrical power generation from insect flight}, booktitle = {SPIE Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring}, pages = {797702--797702}, }

2009

Automatic animal tracking using matched filters and time difference of arrival

Robert B MacCurdy, Richard M Gabrielson, Eric Spaulding, Alejandro Purgue, Kathryn A Cortopassi, and 1 more author

Journal of Communications, Jun 2009

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A method for tracking animals using a terrestrial system similar to GPS is presented. This system enables simultaneous tracking of thousands of animals with transmitters that are lighter, longer lasting, more accurate and cheaper than other automatic positioning tags. The technical details of this system are discussed and the results of a prototype are shown.
@article{maccurdy2009automatic, year = {2009}, author = {MacCurdy, Robert B and Gabrielson, Richard M and Spaulding, Eric and Purgue, Alejandro and Cortopassi, Kathryn A and Fristrup, Kurt M}, title = {Automatic animal tracking using matched filters and time difference of arrival}, journal = {Journal of Communications}, volume = {4}, number = {7}, pages = {487--495}, }

2008

Real-time, automatic animal tracking using direct sequence spread spectrum

Robert B MacCurdy, Richard M Gabrielson, Eric Spaulding, Alejandro Purgue, Kathryn A Cortopassi, and 1 more author

In EuWiT 2008. European Conference on Wireless Technology, Jun 2008

Runner-up: Best Paper Competition

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A method for tracking animals using a terrestrial system similar to GPS is presented. This system enables simultaneous tracking of thousands of animals with transmitters that are lighter, longer lasting, more accurate and cheaper than other automatic positioning tags. The technical details of this system are discussed and the results of a prototype are shown.
@inproceedings{maccurdy2008real, year = {2008}, author = {MacCurdy, Robert B and Gabrielson, Richard M and Spaulding, Eric and Purgue, Alejandro and Cortopassi, Kathryn A and Fristrup, Kurt M}, title = {Real-time, automatic animal tracking using direct sequence spread spectrum}, booktitle = {EuWiT 2008. European Conference on Wireless Technology}, pages = {53--56}, note = {Runner-up: Best Paper Competition}, }
A methodology for applying energy harvesting to extend wildlife tag lifetime

Robert MacCurdy, Timothy Reissman, Ephrahim Garcia, and David Winkler

In Proceedings of ASME IMECE Conference, IMECE2008, 68082, Jun 2008

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Wildlife monitoring tags are a widely used technique for studying animals in their natural habitats. At present, these devices are energy limited, based on the mass of the electrochemical battery that can be carried by the animal. Flying animals are particularly restricted, based on a requirement for minimal excess loading. This requirement causes tag lifetimes to be far shorter than would be useful from an ecological perspective, particularly for smaller animals. Energy harvesting is being widely adopted in applications where access to permanent power is limited. If applied to wildlife tags, this approach offers the possibility of extending functional lifetimes indefinitely; however, it presents unique challenges. Practical applications on flying animals are extremely mass limited, subject to environmental stress, and operate at very low frequencies. This paper is meant to address the critical issues in the design task, and makes attempts to place bounds on unknown design parameters, based on literature research where applicable, and on experiment when no data exists. We discuss candidate harvester materials, novel data acquisition tools, and a prototype harvester design.
@inproceedings{MacCurdy2008, year = {2008}, author = {MacCurdy, Robert and Reissman, Timothy and Garcia, Ephrahim and Winkler, David}, title = {A methodology for applying energy harvesting to extend wildlife tag lifetime}, booktitle = {Proceedings of ASME IMECE Conference, IMECE2008, 68082}, url = {http://link.aip.org/link/abstract/ASMECP/v2008/i48692/p121/s1}, }
Energy management of multi-component power harvesting systems

Robert B MacCurdy, Timothy Reissman, and Ephrahim Garcia

In The 15th International Symposium on: Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring, Jun 2008

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Recent efforts in power harvesting systems have concentrated primarily on the optimization of isolated energy conversion techniques, such as piezoelectric, electromagnetic, solar, or thermal generators, but have focused less on combining different energy transducer types and have placed less emphasis on storing the converted energy for use by other devices. The purpose of this work is to analyze and present an integrated piezoelectric and electromagnetic power harvesting system utilizing existing technology for energy management and storage. Primary emphasis is on the analysis of the combination of existing, or readily obtainable, energy conversion techniques, operating as a single system, and the energy conversion efficiency of the alternating to direct current management, or storage, circuit.
@inproceedings{MacCurdy2008a, year = {2008}, author = {MacCurdy, Robert B and Reissman, Timothy and Garcia, Ephrahim}, title = {Energy management of multi-component power harvesting systems}, booktitle = {The 15th International Symposium on: Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring}, pages = {692809--692809}, url = {http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=832677}, }
Experimental study of the mechanics of motion of flapping insect flight under weight loading

T. Reissman, R. MacCurdy, and E. Garcia

In Proceedings of ASME SMASIS Conference, SMASIS2008, 661, Jun 2008

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The results of this study are an evaluation of the mechanics of motion of a weight loaded Manduca sexta Hawkmoth during flight using accelerations recorded with an onboard sensory system. Findings indicate that these ‘normal’ flapping insects maintain relatively fixed body frequencies in both free and weight loaded flight, which correspond with the driving frequency, or wing beat frequency. Within the analysis, a presence of a harmonic body frequency at twice the wing beat frequency was also discovered. The conclusions from this study indicate an average excess muscle power of over 40mW available in free, unloaded flight. Stability robustness of these flapping insects in flight using the results of a large payload disturbance, 856mg or nearly half to one-third the mass of insect, is demonstrated, and their usefulness as platform for cyborg MAV (CMAV) development is presented.
@inproceedings{Reissman2008, year = {2008}, author = {Reissman, T. and MacCurdy, R. and Garcia, E.}, title = {Experimental study of the mechanics of motion of flapping insect flight under weight loading}, booktitle = {Proceedings of ASME SMASIS Conference, SMASIS2008, 661}, url = {http://link.aip.org/link/abstract/ASMECP/v2008/i43321/p699/s1}, }