Ferrofluidic Manipulator: Automatic Manipulation of Non-magnetic Microparticles at Air-Ferrofluid Interface

Manipulation of small-scale matter is a fundamental topic in micro- and nanorobotics. Numerous magnetic robotic systems have been developed for the manipulation of microparticles in an ambient environment, liquid as well as on the air-liquid interface. Those systems move intrinsically magnetic or magnetically tagged objects by inducing a magnetic torque or force. However, most of the materials found in nature are non-magnetic. Here, we report a novel ferrofluidic manipulator for automatic two-dimensional manipulation of non-magnetic objects floating on top of a ferrofluid. The manipulation system employs eight centimeter-scale solenoids, which can move non-magnetic particles floating on the air-liquid interface by deforming the air-ferrofluid interface. Using linear programming, we can control the motion of non-magnetic particles with a predefined trajectory of a line, square, and circle with a precision of 57.4+/-33.6 um, 74+/-44.4 um, and 67.2+/-38.6 um, respectively. The ferrofluidic manipulator is versatile with the materials and the shapes of the objects under manipulation. We have successfully manipulated particles made of polyethylene, polystyrene, a silicon chip, and poppy and sesame seeds.