The Experts below are selected from a list of 2403 Experts worldwide ranked by ideXlab platform

Bradley J. Nelson - One of the best experts on this subject based on the ideXlab platform.

  • magnetically actuated Microrobots as a platform for stem cell transplantation
    Science Robotics, 2019
    Co-Authors: Sungwoong Jeon, Sangwon Kim, Cheil Moon, Seungmin Lee, Eunhee Kim, So Yeun Kim, Sun Hwa Park, Jung Ho Jeon, Sung Won Kim, Bradley J. Nelson
    Abstract:

    Magnetic Microrobots were developed for three-dimensional culture and the precise delivery of stem cells in vitro, ex vivo, and in vivo. Hippocampal neural stem cells attached to the Microrobots proliferated and differentiated into astrocytes, oligodendrocytes, and neurons. Moreover, Microrobots were used to transport colorectal carcinoma cancer cells to tumor microtissue in a body-on-a-chip, which comprised an in vitro liver-tumor microorgan network. The Microrobots were also controlled in a mouse brain slice and rat brain blood vessel. Last, Microrobots carrying mesenchymal stem cells derived from human nose were manipulated inside the intraperitoneal cavity of a nude mouse. The results indicate the potential of Microrobots for the culture and delivery of stem cells.

  • Optimization of Tail Geometry for the Propulsion of Soft Microrobots
    IEEE Robotics and Automation Letters, 2017
    Co-Authors: Hen-wei Huang, Qianwen Chao, Mahmut Selman Sakar, Bradley J. Nelson
    Abstract:

    Recent advances in smart materials and microfabrication techniques lead to the development of Microrobots for on-demand and targeted therapy. Self-folded hydrogel tubes are particularly promising vehicles as they provide relatively large surface area-to-volume ratio and cargo space for therapeutic agents. In this paper, we decorate these microstructures with an artificially approximated bacterial flagellum to enable efficient swimming in fluidic environments. Flexibility enhances overall motility of the soft microrobot through synergistic propulsion generated by the tubular body and the flagellum, a feature that has not been observed in conventional Microrobots manufactured from rigid materials. While the flagellum is applying forward thrust, a precession is induced on the body due to wobbling of the tail that can provide extra speed depending on the tail design. A simple model based on resistive force theory explains the direction-dependent changes in swimming motility and the role of tail geometry.

  • real time holographic tracking and control of Microrobots
    International Conference on Robotics and Automation, 2017
    Co-Authors: Ayoung Hong, Olgac Ergeneman, Salvador Pane, Burak Zeydan, Samuel Charreyron, Fatih M Toy, Andrew J Petruska, Bradley J. Nelson
    Abstract:

    Digital holography is used to track the three-dimensional position of a magnetic microrobot maneuvered in real time by means of an electromagnetic manipulation system. The method presented is able to process holograms at 40 Hz with a position accuracy in the imaging plane and in depth of $\pm$ 23 and $\pm$ 180  $\mu$ m, respectively. As this method does not require magnification, Microrobots can be tracked in significantly larger working volumes than conventional optical methods. The performance of this tracking method is demonstrated by visually servoing a magnetic bead around a cubic trajectory.

  • behavior of rotating magnetic Microrobots above the step out frequency with application to control of multi microrobot systems
    Applied Physics Letters, 2014
    Co-Authors: Arthur W Mahoney, Bradley J. Nelson, Nathan D Nelson, Kathrin E Peyer, Jake J Abbott
    Abstract:

    This paper studies the behavior of rotating magnetic Microrobots, constructed with a permanent magnet or a soft ferromagnet, when the applied magnetic field rotates faster than a microrobot's step-out frequency (the frequency requiring the entire available magnetic torque to maintain synchronous rotation). A microrobot's velocity dramatically declines when operated above the step-out frequency. As a result, it has generally been assumed that Microrobots should be operated beneath their step-out frequency. In this paper, we report and demonstrate properties of a microrobot's behavior above the step-out frequency that will be useful for the design and control of multi-microrobot systems.

  • fabrication and characterization of magnetic Microrobots for three dimensional cell culture and targeted transportation
    Advanced Materials, 2013
    Co-Authors: Sangwon Kim, Bradley J. Nelson, Li Zhang, Famin Qiu, Samhwan Kim, Ali Ghanbari, Cheil Moon, Hongsoo Choi
    Abstract:

    Magnetically manipulated Microrobots are demonstrated for targeted cell transportation. Full three-dimensional (3D) porous structures are fabricated with an SU-8 photoresist using a 3D laser lithography system. Nickel and titanium are deposited as a magnetic material and biocompatible material, respectively. The fabricated Microrobots are controlled in the fluid by external magnetic fields. Human embryonic kidney 239 (HEK 239) cells are cultivated in the microrobot to show the possibility for targeted cell transportation.

Metin Sitti - One of the best experts on this subject based on the ideXlab platform.

  • zwitterionic 3d printed non immunogenic stealth Microrobots
    Advanced Materials, 2020
    Co-Authors: Pol Cabanach, Metin Sitti, Oncay Yasa, Abdon Penafrancesch, Devin Sheehan, Ugur Bozuyuk, Salvador Borros
    Abstract:

    Microrobots offer transformative solutions for non-invasive medical interventions due to their small size and untethered operation inside the human body. However, they must face the immune system as a natural protection mechanism against foreign threats. Here, non-immunogenic stealth zwitterionic Microrobots that avoid recognition from immune cells are introduced. Fully zwitterionic photoresists are developed for two-photon polymerization 3D microprinting of hydrogel Microrobots with ample functionalization: tunable mechanical properties, anti-biofouling and non-immunogenic properties, functionalization for magnetic actuation, encapsulation of biomolecules, and surface functionalization for drug delivery. Stealth Microrobots avoid detection by macrophage cells of the innate immune system after exhaustive inspection (>90 hours), which has not been achieved in any microrobotic platform to date. These versatile zwitterionic materials eliminate a major roadblock in the development of biocompatible Microrobots, and will serve as a toolbox of non-immunogenic materials for medical microrobot and other device technologies for bioengineering and biomedical applications.

  • elucidating the interaction dynamics between microswimmer body and immune system for medical Microrobots
    Science Robotics, 2020
    Co-Authors: Immihan Ceren Yasa, Metin Sitti, Ugur Bozuyuk, Hakan Ceylan, Annamaria Wild
    Abstract:

    The structural design parameters of a medical microrobot, such as the morphology and surface chemistry, should aim to minimize any physical interactions with the cells of the immune system. However, the same surface-borne design parameters are also critical for the locomotion performance of the Microrobots. Understanding the interplay of such parameters targeting high locomotion performance and low immunogenicity at the same time is of paramount importance yet has so far been overlooked. Here, we investigated the interactions of magnetically steerable double-helical microswimmers with mouse macrophage cell lines and splenocytes, freshly harvested from mouse spleens, by systematically changing their helical morphology. We found that the macrophages and splenocytes can recognize and differentially elicit an immune response to helix turn numbers of the microswimmers that otherwise have the same size, bulk physical properties, and surface chemistries. Our findings suggest that the structural optimization of medical Microrobots for the locomotion performance and interactions with the immune cells should be considered simultaneously because they are highly entangled and can demand a substantial design compromise from one another. Furthermore, we show that morphology-dependent interactions between macrophages and microswimmers can further present engineering opportunities for biohybrid microrobot designs. We demonstrate immunobots that can combine the steerable mobility of synthetic microswimmers and the immunoregulatory capability of macrophages for potential targeted immunotherapeutic applications.

  • rotational flows generated by Microrobots rotating near surfaces at low reynolds number
    arXiv: Fluid Dynamics, 2020
    Co-Authors: Anirban Jana, Metin Sitti
    Abstract:

    In this study, we use numerical simulations to investigate the flow field induced by a single magnetic microrobot rotating with a constant angular speed about an axis perpendicular to an underlying surface. A parallel solver for steady Stokes flow equations based on the boundary-element method is used for simulating these flows. A simple transformation is introduced to extend the predictive capability of the solver to cases with small unsteadiness. Flows induced by four simple robot shapes are investigated: sphere, upright cylinder, horizontally-laid cylinder, and five-pointed star-shaped prism. Shapes with cross-sections that are axisymmetric about the rotation axis (sphere and upright cylinder) generate time-invariant flow fields, which could be useful for applications such as micromanipulation. Non-axisymmetric shapes (horizontally-laid cylinder and the star-shaped prism) induce significant unsteadiness inside the flow field, which could be desirable for applications such as micromixing. Furthermore, a slender horizontally-laid cylinder generates substantially three-dimensional flows, an added benefit for micromixing applications. The presence of nearby walls such as a bottom substrate or sidewalls has a retarding effect on the induced flows, which is quantified. Finally, we present the driving torque and power-consumption of these Microrobots rotating in viscous liquids. The numerical modeling platform used in this work can enable future optimal microrobot designs for a given application requirement.

  • acoustically powered surface slipping mobile Microrobots
    Proceedings of the National Academy of Sciences of the United States of America, 2020
    Co-Authors: Amirreza Aghakhani, Metin Sitti, Oncay Yasa, Paul Wrede
    Abstract:

    Untethered synthetic Microrobots have significant potential to revolutionize minimally invasive medical interventions in the future. However, their relatively slow speed and low controllability near surfaces typically are some of the barriers standing in the way of their medical applications. Here, we introduce acoustically powered Microrobots with a fast, unidirectional surface-slipping locomotion on both flat and curved surfaces. The proposed three-dimensionally printed, bullet-shaped microrobot contains a spherical air bubble trapped inside its internal body cavity, where the bubble is resonated using acoustic waves. The net fluidic flow due to the bubble oscillation orients the microrobot's axisymmetric axis perpendicular to the wall and then propels it laterally at very high speeds (up to 90 body lengths per second with a body length of 25 µm) while inducing an attractive force toward the wall. To achieve unidirectional locomotion, a small fin is added to the microrobot's cylindrical body surface, which biases the propulsion direction. For motion direction control, the Microrobots are coated anisotropically with a soft magnetic nanofilm layer, allowing steering under a uniform magnetic field. Finally, surface locomotion capability of the Microrobots is demonstrated inside a three-dimensional circular cross-sectional microchannel under acoustic actuation. Overall, the combination of acoustic powering and magnetic steering can be effectively utilized to actuate and navigate these Microrobots in confined and hard-to-reach body location areas in a minimally invasive fashion.

  • independent actuation of two tailed Microrobots
    International Conference on Robotics and Automation, 2018
    Co-Authors: Islam S M Khalil, Ahmet Fatih Tabak, Youssef Hamed, Mohamed Tawakol, Anke Klingner, Nesrine Abdelrehim El Gohary, Boris Mizaikoff, Metin Sitti
    Abstract:

    A soft two-tailed microrobot in low Reynolds number fluids does not achieve forward locomotion by identical tails regardless to its wiggling frequency. If the tails are nonidentical, zero forward locomotion is also observed at specific oscillation frequencies (which we refer to as the reversal frequencies), as the propulsive forces imparted to the fluid by each tail are almost equal in magnitude and opposite in direction. We find distinct reversal frequencies for the two-tailed Microrobots based on their tail length ratio. At these frequencies, the microrobot achieves negligible net displacement under the influence of a periodic magnetic field. This observation allows us to fabricate groups of Microrobots with tail length ratio of 1.24 ± 0.11, 1.48 ± 0.08, and 1.71 ± 0.09. We demonstrate selective actuation of Microrobots based on prior characterization of their reversal frequencies. We also implement simultaneous flagellar propulsion of two Microrobots and show that they can be controlled to swim along the same direction and opposite to each other using common periodic magnetic fields. In addition, independent motion control of two Microrobots is achieved toward two different reference positions with average steady-state error of 110.1 ± 91.8 μm and 146.9 ± 105.9 μm.

Robert J Wood - One of the best experts on this subject based on the ideXlab platform.

  • concomitant sensing and actuation for piezoelectric Microrobots
    Smart Materials and Structures, 2018
    Co-Authors: Kaushik Jayaram, Noah T Jafferis, Neel Doshi, Ben Goldberg, Robert J Wood
    Abstract:

    Sensor fabrication for Microrobots is challenging due to their small size and low mass. As a potential solution, we present a technique for estimating the velocity of piezoelectric bending bimorph actuators, a popular choice for driving such microscale devices, that requires simple electronics and no additional mechanical components. Our approach relies on the insight that motion of the actuators causes varying strains on the surface on the piezoelectric material, which via the direct piezoelectric effect, results in a current proportional to the actuator velocity. We propose that the actuator be electrically approximated as a parallel combination of a frequency and voltage dependent resistor and capacitor, and a velocity proportional current source. We develop an experimental procedure to measure these quantities, and are able to experimentally determine the actuator tip velocity to within 10% accuracy over a range of voltages (25–200 V) and frequencies (1–2000 Hz, well beyond actuator resonance). We successfully apply this sensing methodology to two Microrobots, the RoboBee and the Harvard Ambulatory MicroRobot (HAMR), to estimate the wing and limb motion respectively. We further use sensor feedback to close the loop on HAMR's leg phase and obtain desired leg trajectories near transmission resonance. The proposed sensor methodology is generic and can be applied to piezoelectric actuators of different geometries and configurations for uses in microrobotic applications.

  • Bio-inspired mechanisms for inclined locomotion in a legged insect-scale robot
    2014 IEEE International Conference on Robotics and Biomimetics (ROBIO 2014), 2014
    Co-Authors: Benedikt F. Seitz, Neel Doshi, Benjamin Goldberg, Onur Ozcan, David L. Christensen, Elliot W. Hawkes, Mark R. Cutkosky, Robert J Wood
    Abstract:

    Legged locomotion is an open problem in robotics, particularly for non-level surfaces. With decreasing robot size, different issues for climbing mechanisms and their attachment and detachment appear due to the physics of scaling. This paper describes micro-scale phenomena for different adhesion methods that can be employed in Microrobots. These adhesion methods are applied to a sub-2 gram legged robot, the Harvard Ambulatory MicroRobot (HAMR), by leveraging recent advances in milli- and micrometer-scale manufacturing. The presented designs utilize different passively oriented adhesives on the legs of the robot to improve inclined locomotion performance. A 3DoF ankle joint is designed and implemented and the effects of a passive tail are studied. As a result, HAMR's climbing capability is increased from 3° inclines to 22° inclines and 45° declines. Finally, an analytical model of leg and foot force generation is presented and compared with experimental force data from the attachment mechanism on a single-leg experimental setup.

  • biologically inspired optical flow sensing for altitude control of flapping wing Microrobots
    IEEE-ASME Transactions on Mechatronics, 2013
    Co-Authors: Pierreemile J Duhamel, Nestor O Perezarancibia, Geoffrey Barrows, Robert J Wood
    Abstract:

    We present the design and fabrication of a 33-mg 1-D optical-flow-based altitude sensor and its integration with a 68-mg flapping-wing flying microrobot. For the first time, an on-board sensor is successfully used to measure altitude for feedback control in a flyer of this size. Both the control strategy and the sensing system are biologically inspired. The control strategy relies on amplitude modulation mediated by optical-flow sensing. The research presented here is a key step toward achieving the goal of complete autonomy for at-scale flying robotic insects, since this demonstrates that strategies for controlling flapping-wing Microrobots in vertical flight can rely on optical-flow-based on-board sensors. In order to demonstrate the efficacy of the proposed sensing system and suitability of the combined sensing and control strategies, six experimental cases are presented and discussed here.

  • altitude feedback control of a flapping wing microrobot using an on board biologically inspired optical flow sensor
    International Conference on Robotics and Automation, 2012
    Co-Authors: Pierreemile J Duhamel, Nestor O Perezarancibia, Geoffrey Barrows, Robert J Wood
    Abstract:

    We present experimental results on the controlled vertical flight of a flapping-wing flying microrobot, in which for the first time an on-board sensing system is used for measuring the microrobot's altitude for feedback control. Both the control strategy and the sensing system are biologically inspired. The control strategy relies on amplitude modulation mediated by optical flow. The research presented here is a key step toward achieving the goal of complete autonomy for flying Microrobots, since this demonstrates that strategies for controlling flapping-wing Microrobots in vertical flight can rely on optical flow sensors.

  • a review of actuation and power electronics options for flapping wing robotic insects
    International Conference on Robotics and Automation, 2008
    Co-Authors: Michael Karpelson, Guyeon Wei, Robert J Wood
    Abstract:

    Flapping-wing robotic insects require actuators with high power densities at centimeter to micrometer scales. Due to the low weight budget, the selection and design of the actuation mechanism needs to be considered in parallel with the design of the power electronics required to drive it. This paper explores the design space of flapping-wing Microrobots weighing lg and under by determining mechanical requirements for the actuation mechanism, analyzing potential actuation technologies, and discussing the design and realization of the required power electronics. Promising combinations of actuators and power circuits are identified and used to estimate microrobot performance.

Lianqing Liu - One of the best experts on this subject based on the ideXlab platform.

  • superhydrophobic photothermal graphene composites and their functional applications in Microrobots swimming at the air water interface
    Chemical Engineering Journal, 2021
    Co-Authors: Xiaodong Wang, Liguo Dai, Niandong Jiao, Steve Tung, Lianqing Liu
    Abstract:

    Abstract Photoresponsive superhydrophobic Microrobots based on Marangoni effect are attracting more and more attention. Graphene has high photothermal properties and nanostructures. It is an excellent material for manufacturing superhydrophobic Microrobots moving at the air/water interface. However, it is difficult to fabricate superhydrophobic Microrobots with complex shapes moving at the air/water interface using graphene without chemical modification. Herein, Graphene/polydimethylsiloxane composite materials were prepared, which exhibited excellent superhydrophobic and photothermal properties. These properties were systematically investigated under various conditions. The developed material exhibits good manufacturability and can be easily made into a variety of small-scale complex structures and different shapes of Microrobots with superhydrophobic and photothermal properties. With different structures, it is proved that the Microrobots can exhibit a variety of motions, including linear, rotary, and oscillatory, under the action of infrared light. Combined with mechanical analysis, the three motion forms can be integrated into a single microrobot. Finally, a water strider-like robot is fabricated, that can glide and 180° roll-over jump on the water surface, exhibiting good infrared light driving performance and magnetic controllability. This work not only presents a method to prepare superhydrophobic Microrobots based on graphene, but also provides a reference for the development of multifunctional Microrobots, and further promotes the application of Microrobots in liquid detection and oil recovery.

  • Integrated Assembly and Flexible Movement of Microparts Using Multifunctional Bubble Microrobots.
    ACS applied materials & interfaces, 2020
    Co-Authors: Liguo Dai, Daojing Lin, Xiaodong Wang, Niandong Jiao, Lianqing Liu
    Abstract:

    Industrial robots have been widely used for manufacturing and assembly in factories. However, at the microscale, most assembly technologies can only pattern the micromodules together loosely and can hardly combine the micromodules to directly form an entity that cannot be easily dispersed. In this study, surface bubbles are made to function as Microrobots on a chip. These Microrobots can move, fix, lift, and drop microparts and integratively assemble them into a tightly connected entity. As an example, the assembly of a pair of microparts with dovetails is considered. A jacklike bubble robot is used to lift and drop a micropart with a tail, whereas a mobile microrobot is used to push the other micropart with the corresponding socket to the proper position so that the tail can be inserted into the socket. The assembled microparts with the tail-socket joint can move as an entity without separation. Similarly, different types of parts are integratively assembled to form various structures such as gears, snake-shaped chains, and vehicles, which are then driven by bubble Microrobots to perform different forms of movement. This assembly technology is simple and efficient and is expected to play an important role in micro-operation, modular assembly, and tissue engineering.

  • automatic path tracking and target manipulation of a magnetic microrobot
    Micromachines, 2016
    Co-Authors: Jingyi Wang, Niandong Jiao, Steve Tung, Lianqing Liu
    Abstract:

    Recently, wireless controlled Microrobots have been studied because of their great development prospects in the biomedical field. Electromagnetic Microrobots have the advantages of control agility and good precision, and thus, have received much attention. Most of the control methods for controlling a magnetic microrobot use manual operation. Compared to the manual method, the automatic method will increase the accuracy and stability of locomotion and manipulation of Microrobots. In this paper, we propose an electromagnetic manipulation system for automatically controlling the locomotion and manipulation of Microrobots. The microrobot can be automatically controlled to track various paths by using visual feedback with an expert control algorithm. A positioning accuracy test determined that the position error ranges from 92 to 293 μm, which is less than the body size (600 μm) of the microrobot. The velocity of the microrobot is nearly proportional to the applied current in the coils, and can reach 5 mm/s. As a micromanipulation tool, the microrobot is used to manipulate microspheres and microgears with the automatic control method. The results verify that the microrobot can drag, place, and drive the microstructures automatically with high precision. The microrobot is expected to be a delicate micromachine that could play its role in microfluidics and blood vessels, where conventional instruments are hard to reach.

  • controlled regular locomotion of algae cell Microrobots
    Biomedical Microdevices, 2016
    Co-Authors: Shuangxi Xie, Niandong Jiao, Steve Tung, Lianqing Liu
    Abstract:

    Algae cells can be considered as Microrobots from the perspective of engineering. These organisms not only have a strong reproductive ability but can also sense the environment, harvest energy from the surroundings, and swim very efficiently, accommodating all these functions in a body of size on the order of dozens of micrometers. An interesting topic with respect to random swimming motions of algae cells in a liquid is how to precisely control them as Microrobots such that they swim according to manually set routes. This study developed an ingenious method to steer swimming cells based on the phototaxis. The method used a varying light signal to direct the motion of the cells. The swimming trajectory, speed, and force of algae cells were analyzed in detail. Then the algae cell could be controlled to swim back and forth, and traverse a crossroad as a microrobot obeying specific traffic rules. Furthermore, their motions along arbitrarily set trajectories such as zigzag, and triangle were realized successfully under optical control. Robotize algae cells can be used to precisely transport and deliver cargo such as drug particles in microfluidic chip for biomedical treatment and pharmacodynamic analysis. The study findings are expected to bring significant breakthrough in biological drives and new biomedical applications.

Jake J Abbott - One of the best experts on this subject based on the ideXlab platform.

  • behavior of rotating magnetic Microrobots above the step out frequency with application to control of multi microrobot systems
    Applied Physics Letters, 2014
    Co-Authors: Arthur W Mahoney, Bradley J. Nelson, Nathan D Nelson, Kathrin E Peyer, Jake J Abbott
    Abstract:

    This paper studies the behavior of rotating magnetic Microrobots, constructed with a permanent magnet or a soft ferromagnet, when the applied magnetic field rotates faster than a microrobot's step-out frequency (the frequency requiring the entire available magnetic torque to maintain synchronous rotation). A microrobot's velocity dramatically declines when operated above the step-out frequency. As a result, it has generally been assumed that Microrobots should be operated beneath their step-out frequency. In this paper, we report and demonstrate properties of a microrobot's behavior above the step-out frequency that will be useful for the design and control of multi-microrobot systems.

  • octomag an electromagnetic system for 5 dof wireless micromanipulation
    IEEE Transactions on Robotics, 2010
    Co-Authors: Michael P Kummer, Jake J Abbott, Bradley E Kratochvil, Ruedi Borer, Ali Sengul, Bradley J. Nelson
    Abstract:

    We demonstrate five-degree-of-freedom (5-DOF) wireless magnetic control of a fully untethered microrobot (3-DOF position and 2-DOF pointing orientation). The microrobot can move through a large workspace and is completely unrestrained in the rotation DOF. We accomplish this level of wireless control with an electromagnetic system that we call OctoMag. OctoMag's unique abilities are due to its utilization of complex nonuniform magnetic fields, which capitalizes on a linear representation of the coupled field contributions of multiple soft-magnetic-core electromagnets acting in concert. OctoMag was primarily designed to control intraocular Microrobots for delicate retinal procedures, but it also has potential uses in other medical applications or micromanipulation under an optical microscope.

  • Microrobots for minimally invasive medicine
    Annual Review of Biomedical Engineering, 2010
    Co-Authors: Bradley J. Nelson, Ioannis K Kaliakatsos, Jake J Abbott
    Abstract:

    Microrobots have the potential to revolutionize many aspects of medicine. These untethered, wirelessly controlled and powered devices will make existing therapeutic and diagnostic procedures less invasive and will enable new procedures never before possible. The aim of this review is threefold: first, to provide a comprehensive survey of the technological state of the art in medical Microrobots; second, to explore the potential impact of medical Microrobots and inspire future research in this field; and third, to provide a collection of valuable information and engineering tools for the design of medical Microrobots.

  • how should Microrobots swim
    International Symposium on Robotics, 2009
    Co-Authors: Jake J Abbott, Li Zhang, Kathrin E Peyer, Marco Cosentino Lagomarsino, Lixin Dong, Ioannis K Kaliakatsos, Bradley J. Nelson
    Abstract:

    Microrobots have the potential to dramatically change many aspects of medicine by navigating through bodily fluids to perform targeted diagnosis and therapy. Researchers have proposed numerous micro-robotic swimming methods, with the vast majority utilizing magnetic fields to wirelessly power and control the microrobot. In this paper, we compare three promising methods of microrobot swimming (using magnetic fields to rotate helical propellers that mimic bacterial flagella, using magnetic fields to oscillate a magnetic head with a rigidly attached elastic tail, and pulling directly with magnetic field gradients) considering practical hardware limitations in the generation of magnetic fields. We find that helical propellers and elastic tails have very comparable performance, and they generally become more desirable than gradient pulling as size decreases and as distance from the magnetic-field-generation source increases. We provide a discussion of why helical propellers are likely the best overall choice for in vivo applications.

  • measuring the magnetic and hydrodynamic properties of assembled mems Microrobots
    International Conference on Robotics and Automation, 2007
    Co-Authors: Michael P Kummer, Jake J Abbott, Karl Vollmers, Bradley J. Nelson
    Abstract:

    Microrobots experience physical phenomena that are difficult to model analytically and that are not completely captured with macro-scale prototypes. In this paper we present a reconfigurable robotic measurement system to characterize the magnetic and hydrodynamic properties of assembled-MEMS Microrobots. The system consists of a powerful permanent magnet that is position controlled with a linear stage. The magnetic field is accurately characterized. Precision sensors are used to measure magnetic force as a function of applied field. The system is first used to validate an existing model for the magnetic force on a soft-magnetic ellipsoid. Next, the magnetic force on a soft-magnetic assembled-MEMS microrobot as a function of the applied field is measured experimentally. Finally, a vision tracking system is integrated with the setup to measure the hydrodynamic properties of the microrobot. The coefficient of viscous friction for the microrobot is obtained experimentally.