Two-Dimensional Contact and Noncontact Micromanipulation in Liquid Using an Untethered Mobile Magnetic Microrobot |
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Abstract: | This paper presents the manipulation of microspheres under water by use of an untethered electromagnetically actuated magnetic microrobot (Mag-$mu$Bot), with dimensions $hbox{250} times hbox{130} times hbox{100} mu$ m$^3$. Manipulation is achieved by two means: contact and noncontact pushing modes. In contact manipulation, the Mag-$mu$Bot is used to physically push the microspheres. In noncontact manipulation, the fluid flow generated by the translation of the Mag-$mu$Bot 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., $hbox{50}$ and $hbox{230}, mu$m 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. |
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