Ferrofluidic Manipulator: Automatic Manipulation of Nonmagnetic Microparticles at the 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. These systems move intrinsically magnetic or magnetically tagged objects by inducing a magnetic torque or force. However, most of the materials found in nature are nonmagnetic. Here, we report a ferrofluidic manipulator for automatic 2-D manipulation of nonmagnetic objects floating on top of a ferrofluid. The manipulation system employs 8-cm-scale solenoids, which can move nonmagnetic particles by deforming the air–ferrofluid interface. Using linear programming, we can control the motion of the nonmagnetic particles with a predefined trajectory of a line, square, and circle with a precision of 25.1
$ \pm $
19.5, 34.4
$ \pm $
28.4, and 33.4
$ \pm $
26.6 μm, 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. This article shows a promising venue for the manipulation of living and nonliving matter at the air–liquid interface.