Selectively Controlled Magnetic Microrobots with Opposing Helices

Magnetic microrobots that swim through liquid media are of interest for minimally invasive medical procedures, bioengineering, and manufacturing. Many of the envisaged applications, such as micromanipulation and targeted cargo delivery, necessitate the use and adequate control of multiple microrobots, which will increase the velocity, robustness, and efficacy of a procedure. While various methods involving heterogeneous geometries, magnetic properties, and surface chemistries have been proposed to enhance independent control, the main challenge has been that the motion between all microwsimmers remains coupled through the global control signal of the magnetic field. Katsamba and Lauga proposed transchiral microrobots, a theoretical design with magnetized spirals of opposite handedness. The competition between the spirals can be tuned to give an intrinsic nonlinearity that each device can function only within a given band of frequencies. This allows individual microrobots to be selectively controlled by varying the frequency of the rotating magnetic field. Here we present the experimental realization and characterization of transchiral micromotors composed of independently driven magnetic helices. We show a swimming micromotor that yields negligible net motion until a critical frequency is reached and a micromotor that changes its translation direction as a function of the frequency of the rotating magnetic field. This work demonstrates a crucial step towards completely decoupled and addressable swimming magnetic microrobots

Crowdsourcing Swarm Manipulation Experiments: A Massive Online User Study with Large Swarms of Simple Robots

Micro- and nanorobotics have the potential to revolutionize many applications including targeted material delivery, assembly, and surgery. The same properties that promise breakthrough solutions---small size and large populations---present unique challenges to generating controlled motion. We want to use large swarms of robots to perform manipulation tasks; unfortunately, human-swarm interaction studies as conducted today are limited in sample size, are difficult to reproduce, and are prone to hardware failures. We present an alternative. This paper examines the perils, pitfalls, and possibilities we discovered by launching SwarmControl.net, an online game where players steer swarms of up to 500 robots to complete manipulation challenges. We record statistics from thousands of players, and use the game to explore aspects of large-population robot control. We present the game framework as a new, open-source tool for large-scale user experiments. Our results have potential applications in human control of micro- and nanorobots, supply insight for automatic controllers, and provide a template for large online robotic research experiments.Comment: 8 pages, 13 figures, to appear at 2014 IEEE International Conference on Robotics and Automation (ICRA 2014

Retrieval of magnetic medical microrobots from the bloodstream

Untethered magnetic microrobots hold the potential to penetrate hard-to-reach areas of the human body and to perform therapy in a controlled way. In the past decade, impressive advancements have been made in this field but the clinical adoption of magnetoresponsive microrobots is still hampered by safety issues. A tool appointed for magnetic microrobots retrieval within body fluids could enable a real paradigm change, fostering their clinical translation.By starting from the general problem to retrieve magnetic microrobots injected into the bloodstream, the authors introduce a magnetic capture model that allows to design retrieval tools for magnetic cores of different diameters (down to 10 nm) and in different environmental conditions (fluid speed up to 7 cms-1). The model robustness is demonstrated by the design and testing of a retrieval catheter. In its optimal configuration, the catheter includes 27 magnets and fits a 12 F catheter. The model provides a good prediction of capture efficiency for 250 nm magnetic particles (experimental data: 77.6%, model prediction: 65%) and a very good prediction for 500 nm particles (experimental data: 93.6%, model prediction: 94%). The results support the proposed model-based design approach, which can be extended to retrieve other magnetoresponsive agents from body compartments

Microfluidics and Bio-MEMS for Next Generation Healthcare.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2018

Fabrication and Characterization of Nickel Plated Micro-resonators for Noncommutative Orientation Control in Microrobots

This thesis describes a procedure for fabricating arrays of microstructures out of SU-8 photoresist and nickel, which was developed with the goal of yielding microrobots capable of 1D rotation byway of magnetically-induced beam vibration that could be used for non-commutative orientation control. Several multi-layer geometries were designed, fabricated, tested and refined. In this process, micro-adhesion of multiple SU-8 layers was also studied. A method for depositing nickel via electroless plating was also developed, tested and characterized. While no microrobots were shown to produce rotation, the final results included beams that were capable of magnetically-induced vibration when subjected to an AC magnetic field. These samples were characterized to determine resonant frequency of the individual beams

pros and cons magnetic versus optical microrobots

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Doctor of Philosophy

dissertationThis dissertation presents results documenting advancements on the control of untethered magnetic devices, such as magnetic \microrobots" and magnetically actuated capsuleendoscopes, motivated by problems in minimally invasive medicine. This dissertationfocuses on applying rotating magnetic elds for magnetic manipulation. The contributions include advancements in the way that helical microswimmers (devices that mimicthe propulsion of bacterial agella) are controlled in the presence of gravitational forces, advancements in ways that groups of untethered magnetic devices can be dierentiated and semi-independently controlled, advancements in the way that untethered magnetic device can be controlled with a single rotating permanent magnet, and an improved understanding in the nature of the magnetic force applied to an untethered device by a rotating magnet

ModMag: A Modular Magnetic Micro-Robotic Manipulation Device

Electromagnetic systems have been used extensively for the control magnetically actuated objects, such as in microrheology and microrobotics research. Therefore, optimizing the design of such systems is highly desired. Some of the features that are lacking in most current designs are compactness, portability, and versatility. Portability is especially relevant for biomedical applications in which in vivo or in vitro testing may be conducted in locations away from the laboratory microscope. This document describes the design, fabrication and implementation of a compact, low cost, versatile, and user friendly device (the ModMag) capable of controlling multiple electromagnetic setups, including a two-dimensional 4-coil traditional configuration, a 3-dimensional Helmholtz configuration, and a 3-dimensional magnetic tweezer configuration. All electronics and circuitry for powering the systems is contained in a compact 10"x6"x3" system which includes a 10" touchscreen. A graphical user interface provides additional ease of use. The system can also be controlled remotely, allowing for more flexibility and the ability to interface with other software running on the remote computer such as propriety camera software. Aside from the software and circuitry, we also describe the design of the electromagnetic coil setups and provide examples of the use of the ModMag in experiments