Wuming Jing

A magnetic thin film microrobot with two operating modes

Magnetic principles have proved successful for untethered submillimeter microrobotics, although challenges still exist in areas of propulsion and control. This paper presents the design, analysis, and performance results for a bimorph thin film magnetic microrobot utilizing the magnetostrictive principle as a secondary oscillating operation mode. The microrobot is no larger than 580 µm in its planar dimension and its total thickness is less than 5 µm. As a robot with magnetic material, it can be operated in a pushing/pulling mode in orthogonal directions for movement in a plane, while its powered with an external magnetic field as low as 1 mT. For the secondary oscillating operation mode utilizing the magnetostrictive principle, in-plane strain is induced, resulting in bending and blocking forces on the robot. These forces are theoretically calculated to prove enough drive force can be generated in this mode. The design is further abstracted and translated into a piezoelectric cantilever FEM model to confirm the theorectical results. Microrobot fabrication and test-bed development based on this analysis is shown, which enabled us to participate in the final competition in the 2010 NIST Mobile Microrobot Challenge, with good performance in the dash and freestyle events. Finally, we discuss the testing results in various dry and fluid environments along with recommendations for future investigation and improvements. Keywords: microrobot, magnetostrictive, bimorph

A Magnetic Microrobot with in situ Force Sensing Capabilities

This paper presents a proof-of-concept prototype of a micro force sensing mobile microrobot. The design consists of a planar, elastic mechanism serving as computer vision-based force sensor module, while the microrobot body is made from a magnetic layer driven by a magnetic field. From observing the deformation of the elastic mechanism, manipulation forces can be determined. The deformation is tracked by a CCD camera attached to an optical microscope. This design is validated through experimental tests with a micromachined prototype. The preliminary results verify this first microrobot prototype is indeed capable of in situ force sensing. This concept can be scaled down further for next generation designs and can be designed for real biomedical applications on microscale.

Towards Independent Control of Multiple Magnetic Mobile Microrobots

In this paper, we have developed an approach for independent autonomous navigation of multiple microrobots under the influence of magnetic fields and validated it experimentally. We first developed a heuristics based planning algorithm for generating collision-free trajectories for the microrobots that are suitable to be executed by an available magnetic field. Second, we have modeled the dynamics of the microrobots to develop a controller for determining the forces that need to be generated for the navigation of the robots along the trajectories at a suitable control frequency. Next, an optimization routine is developed to determine the input currents to the electromagnetic coils that can generate the required forces for the navigation of the robots at the controller frequency. We then validated our approach by simulating an electromagnetic system that contains an array of sixty-four magnetic microcoils designed for generating local magnetic fields suitable for simultaneous independent actuation of multiple microrobots. Finally, we prototyped an mm-scale version of the system and present experimental results showing the validity of our approach.

A tumbling magnetic microrobot with flexible operating modes

This paper presents a magnetic tumbling microrobot design at the micro-scale with flexible operating modes. The microrobot has a dumb-bell shape whose largest dimension is 400 μm. When subjected to an exterior predefined magnetic field, the magnetic microagent performs a tumbling motion driven by the interacting magnetic forces and momentums. By switching the magnetic field during the motion cycle the agent is also able to perform a sliding locomotion that is useful for micromanipulation. The magnetic field providing the drive force is generated by a portable coil system consisting of five electromagnetic coils. Under the available driven field, the prototype has shown adaptable mobility through tumbling mechanism on various types of surface in both dry and fluid environments, and also shown pushing manipulation in viscous fluid. This manipulation force has been experimentally evaluated through testing with AFM tip and a micro force sensor and shown to be on the order of several μNs.

Path Planning and Control for Autonomous Navigation of Single and Multiple Magnetic Mobile Microrobots

In this paper, we have developed an approach for autonomous navigation of single and multiple microrobots under the influence of magnetic fields generated by electromagnetic coils. Our approach consists of three steps. First, we have developed a heuristics based planning algorithm for generating collision-free trajectories for the microrobots that are suitable to be executed by the available magnetic field. Second, we have modeled the dynamics of the microrobots to develop a controller for determining the forces that need to be generated for the navigation of the robots along the trajectories at a suitable control frequency. Finally, an optimization routine is developed to determine the input currents to the electromagnetic coils that can generate the required forces for the navigation of the robots at the controller frequency. We have validated our approach by simulating two electromagnetic coil systems. The first system has four electromagnetic coils designed for actuating a single microrobot. The second system has an array of sixty-four magnetic microcoils designed for generating local magnetic fields suitable for simultaneous independent actuation of multiple microrobots.Copyright

Incorporating in-situ force sensing capabilities in a magnetic microrobot

This paper presents the preliminary design of a micro force sensing mobile microrobot. The design consists of a planar, vision-based micro force sensor end-effector, while the microrobot body is made from a nickel magnetic layer driven by an exterior magnetic field. With a known stiffness, the manipulation forces can be determined from observing the deformation of the end-effector through a CCD camera attached to an optical microscope. After analyzing and calibrating the stiffness of a micromachined prototype, manipulation tests are conducted to verify this microrobot prototype is indeed capable of in situ force sensing while performing a manipulation task. This concept can be scaled down further for next generation designs targeting real biomedical applications on microscale.

A Micro-Scale Magnetic Tumbling Microrobot

This paper presents a magnetic tumbling microrobot design at the micro-scale. The microrobot has a dumbbell shape whose largest dimension is about 400 μm. When subjected to an exterior predefined magnetic field, the magnetic microagent performs a tumbling motion driven by the interacting magnetic forces and momentums. The magnetic field providing driven force is generated by a coil system consisting of five electromagnetic coils. Under the available driven field, we show that the prototype agent is able to tumble on various types of surfaces in both dry and fluid environments.Copyright

Micro-force sensing mobile microrobots

This paper presents the first microscale micro force sensing mobile microrobot. The design consists of a planar, vision-based micro force sensor end-effector, while the microrobot body is made from photoresist mixed with nickel particles that is driven by an exterior magnetic field. With a known stiffness, the manipulation forces can be determined from observing the deformation of the end-effector through a camera attached to an optical microscope. After analyzing and calibrating the stiffness of a micromachined prototype, proof of concept tests are conducted to verify this microrobot prototype possessing the mobility and in-situ force sensing capabilities. This microscale micro-Force Sensing Mobile Microrobot (μFSMM) is able to translate with the speed up to 10 mm=s in a fluid environment. The calibrated stiffness of the micro force sensor end-effector of the μFSMM is on the order of 10-2 N=m. The force sensing resolution with the current vision system is approximately 100 nN.

Towards Functional Mobile Magnetic Microrobots

This chapter covers some fundamental work towards realizing functional mobile magnetic microrobots. First, the theoretical fundamentals of electromagnetism are presented. Second, an electromagnetic testbed design for controlling mobile magnetic microrobots is described. It is utilized to perform benchmarking tests on a simple I-bar shaped magnetic microrobot design. After benchmarking, the critical aspects for micro scale robots and two specific microrobot designs are developed addressing the application needs of biomedical and micro manufacturing tasks. They exhibit tumbling and crawling locomotion mechanisms, respectively. Finally, a magnet microrobot body and vision-based force sensor end-effector combination illustrates an approach for combining different technologies together to create the truly functional mobile magnetic microrobots of the future.

Design of Microscale Magnetic Tumbling Robots for Locomotion in Multiple Environments and Complex Terrains

This paper presents several variations of a microscale magnetic tumbling (μTUM) robot capable of traversing complex terrains in dry and wet environments. The robot is fabricated by photolithography techniques and consists of a polymeric body with two sections with embedded magnetic particles aligned at the ends and a middle nonmagnetic bridge section. The robot’s footprint dimensions are 400 μm × 800 μm. Different end geometries are used to test the optimal conditions for low adhesion and increased dynamic response to an actuating external rotating magnetic field. When subjected to a magnetic field as low as 7 mT in dry conditions, this magnetic microrobot is able to operate with a tumbling locomotion mode and translate with speeds of over 60 body lengths/s (48 mm/s) in dry environments and up to 17 body lengths/s (13.6 mm/s) in wet environments. Two different tumbling modes were observed and depend on the alignment of the magnetic particles. A technique was devised to measure the magnetic particle alignment angle relative to the robot’s geometry. Rotational frequency limits were observed experimentally, becoming more prohibitive as environment viscosity increases. The μTUM’s performance was studied when traversing inclined planes (up to 60°), showing promising climbing capabilities in both dry and wet conditions. Maximum open loop straight-line trajectory errors of less than 4% and 2% of the traversal distance in the vertical and horizontal directions, respectively, for the μTUM were observed. Full directional control of μTUM was demonstrated through the traversal of a P-shaped trajectory. Additionally, successful locomotion of the optimized μTUM design over complex terrains was also achieved. By implementing machine vision control and/or embedding of payloads in the middle section of the robot, it is possible in the future to upgrade the current design with computer-optimized mobility through multiple environments and the ability to perform drug delivery tasks for biomedical applications.