In this paper, we propose methods to control multiple untethered magnetic microrobots (called Mag-μBots), with all dimensions under 1 mm, without the need for a specialized surface. We investigate sets of Mag-μBots that are geometrically designed to respond uniquely to the same applied magnetic fields. By controlling the magnetic field waveforms, individual and subgroups of Mag-μBots are able to locomote in a parallel but dissimilar fashion. The control of geometrically dissimilar Mag-μBots and a group of identically fabricated Mag-μBots are investigated, and control strategies are developed for 1-D and 2-D motion. This is accomplished by learning the velocity response of each microrobot to various control signals and using the uniqueness of each microrobot response to achieve independent control. The effect of high-level control parameters are investigated in simulation and in experiments, and the simultaneous independent global positioning of two and three microrobots is demonstrated in 2-D space. As this control method is accomplished without the use of a specialized surface, it has potential applications in areas such as microfluidic systems and biomanipulation.

This study develops autonomous manipulation strategies for a mobile untethered microrobot that operates on a 2-D surface in a fluidic environment. The microrobot, which is a permanent magnet, is under m in all dimensions and is actuated by oscillating external magnetic fields. Two types of manipulations are considered: 1) front pushing, where the microrobot pushes a micro-object by direct contact; and 2) side pushing, which can result in noncontact pushing, where the fluid flow fields that are generated by a translating microrobot are used to displace a micro-object. Physical models are provided to estimate the displacement of the micro-object due to the fluid motion. Model-based controllers to perform contact and noncontact manipulation are proposed, which iteratively correct emerging manipulation behaviors to improve performance. It is found that using a model-based solution as a feed-forward input, which is combined with a learning controller, can significantly improve micro-object pushing performance. Finally, we begin to address the problem to assemble two micro-objects together using the microrobot, which is only successful by using a side-pushing method.

In this work, we develop methods for controlling multiple untethered magnetic micro-robots (called Mag-μBots), with all dimensions under 1 mm, without the need for a specialized surface. We investigate sets of Mag-μBots that are geometrically and magnetically designed to respond uniquely to the same magnetic fields. The responses of geometrically dissimilar Mag-μBots with similar magnetization and a group of identically-fabricated Mag-μBots are investigated. By controlling the magnetic field waveforms, individual and subgroups of Mag-μBots are able to locomote in a parallel but dissimilar fashion. Specifically, the pulsing frequency of the imposed driving magnetic fields is used as a selection method among the Mag-μBots. This method for accomplishing motion discrimination is discussed, modeled, and tested. Independent global positioning of two and three robots is demonstrated in two-dimensional space. While individual Mag-μBot velocities can be as high as 7 mm/s, the effective velocities during multi robot control are found to be up to 2 mm/s. As this control method is accomplished without the use of a specialized surface, it has potential applications in areas such as micro-fluidic systems and bio-manipulation.

A primary challenge in the field of reconfigurable robotics is scaling down the size of individual robotic modules. We present a novel set of permanent magnet modules that are under 1 mm in all dimensions, called Mag-μMods, for use in a reconfigurable micro-system. The modules are actuated by oscillating external magnetic fields of several mT in strength, and are capable of locomoting on a 2-D surface. Multiple modules are controlled using an electrostatic anchoring surface, which selectively prevents specific modules from being driven by the external field, while allowing others to move freely. We model the processes of both assembling and disassembling two modules by analyzing the forces the modules experience, and experimentally verify the accuracy of the models. For disassembly, we employ electrostatic anchoring and externally applied magnetic torques to successfully separate the modules.

A quadrupedal robot inspired by the basilisk lizard was developed and modeled with a 3D real time simulation. Due to the robot's geometry, leg motion, and water interactions, the net pitch moment at the center of mass is not zero making pitch motion unstable. This paper introduces two types of tails, passive and active, to stabilize pitch motion and analyzes the advantages and disadvantages of each. It is shown in simulation that a purely passive tail can stabilize pitch motion and lead to a steady state robot pitch angle in the absence of disturbances. It is further shown that an active tail can compensate for disturbances and correct any drift in the robot body pitch angle due to changes in robot running speed.

This work presents the control of multiple untethered rectilinear magnetic micro-robots (Mag-¿Bots) with dimensions 250 × 130 × 100 ¿m3actuated by pulsed external magnetic fields, which translate by induced stick-slip motion at speeds of up to 4 mm/s immersed in silicone oil. Multiple Mag-¿Bot control is enabled by employing an array of individually addressable electrostatic surfaces to selectively anchor individual Mag-¿Bots. Coupled parallel and uncoupled serial motion of multiple robots is demonstrated, and they can combine to form an assembly that is also capable of motion. Manipulation of 230 ¿m diameter microspheres is also demonstrated cooperatively by two Mag-¿Bots in a fluid environment, and is enhanced when the two Mag-¿Bots are combined. An analysis of the electrostatic anchoring forces and the forces relevant to manipulation is discussed.

This paper presents the manipulation of microspheres under water by use of an untethered electromagnetically actuated magnetic microrobot (Mag-muBot), with dimensions 250 times 130 times 100 mum3. Manipulation is achieved by two means: contact and noncontact pushing modes. In contact manipulation, the Mag-muBot is used to physically push the microspheres. In noncontact manipulation, the fluid flow generated by the translation of the Mag-muBot is used to push the microspheres. Modeling of the system is performed, taking into account micrometer-scale surface forces and fluid drag effects to determine the motion of a sphere within a robot-generated fluid flow. Fluid drag models for free-stream flow and formulations for near-wall flow are both analyzed and compared with the experiments, in which pushing of two sphere sizes, i.e., 50 and 230 mum diameters, is characterized in a controlled, robot-generated flow. Dynamic simulations are provided using the developed physical models to capture this behavior. We find that the near-wall physical models are, in general, in agreement with the experiment, and free-stream models overestimate microsphere motion.

The water runner robot is designed to run on the surface of water in a manner similar to the basilisk lizard. To do so, it must generate a lift force greater than its weight by slapping and stroking its foot through the water, creating an air cavity in the process. In addition, it must remove its foot before this cavity collapses. Basilisk lizards deal with this problem by folding their feet during retraction from the air cavity to avoid prematurely collapsing the cavity and generating excess drag. Several different passive foot designs for the water runner were analyzed to determine which had the largest lift and created the least amount of drag. Feet with folding sections which collapse during retraction and spring back into place once the foot has exited the water were found to work best. Those feet which allowed air to pass through during retraction provided the least net lift. Elliptic feet with their major axis in line with the direction of running performed better than simple circular feet. Consequences of these results are discussed.

This work presents an untethered magnetic micro- robot with dimensions of 250mumx 130mumx 100mum. The robot is composed entirely of neodymium-iron-boron fabricated using laser micro-machining. It is actuated by a system of five macro-scale electromagnets. By using electromagnets to control the robot, the surface on which the robot operates need not be specialized, smooth, patterned, nor conductive. Two control methods, both based on periodic excitation of the robot, are attempted and compared. Controllable motion at speeds in excess of 2.8 mm/s, approximately 11 body lengths per second, is demonstrated. Teleoperated motion in two dimensions is shown, and the assembly of micro-particles is demonstrated underwater. Potential future applications include micro-scale manipulation, fabrication, and assembly of micro-systems.

This paper proposes a 3-D dynamic simulation of a previously developed basilisk lizard inspired quadruped robot, which is capable of locomotion on the surface of water. Using this 3-D simulation along with several 1-D and 2-D models, stability in terms of robot elevation from the water surface and robot rolling are examined. Analysis of the lifting force shows the robot is capable of running on water using viscous drag forces. Using this analysis, a criterion for convergence to a steady state distance from the water is presented. It is determined that 7-12 Hz is an appropriate running frequency range for the robot to lift its weight. Compliant footpads are found to be beneficial in reducing the force associated with pulling out of the water. Further, from the roll motion analysis, previous designs result in instability along the roll axis. By comparing leg running frequency to the bodypsilas roll frequency, the minimum required roll moment of inertia for stable roll motion can be determined.

This paper describes the design and development of a novel robot, which attempts to emulate the basilisk lizard's ability to run on the surface of water. Previous studies of the lizards themselves have characterized their means of staying afloat. The design of a biomimetic robot utilizing similar principles is discussed, modeled, and prototyped. Functionally, the robot uses a pair of identical four bar mechanisms, with a 180degphase shift to achieve locomotion on the water's surface. Simulations for determining robot lift and power requirements are presented. Through simulation and experimentation, parameters are varied with the focus being a maximization of the ratio of lift to power. Four legged robots were more easily stabilized, and had a higher lift-to-power ratio than two legged robots. Decreases in characteristic length and running speed, and increases in foot diameter and foot penetration depth all cause a higher lift to power ratio. Experimental lift approached 80 gr, and experimental performance exceeded 12 gr/W for four legged robots with circular feet. This work opens the door for legged robots to become ambulatory over both land and water, and represents a first step toward robots which run on the water instead of floating or swimming.

This paper introduces a novel robot which can run on the surface of water in a manner similar to basilisk lizards. Previous studies on the lizards themselves have characterized their method of propulsion and their means of staying afloat. By slapping and stroking their feet into the water, the lizard effects a momentum transfer which provides both forward thrust and lift. The design of a biomimetic robot utilizing similar principles is discussed, modeled, and prototyped. Functionally, the robot uses a pair of identical four bar mechanisms, with a 180deg phase shift to achieve bipedal locomotion on the water's surface. Computational and experimental results are presented and reviewed with the focus being a maximization of the lift to power ratio. After optimization, two legged models can experimentally provide 12-15 g/W of lift while four legged models can provide 50 g/W of lift. This work opens the door for bipedal and quadrupedal robots to become ambulatory over both land and water, and represents a first step toward studies in amphibious stride patterns; step motions equally conducive to propulsion on water and land