Magnetomechanical Transport of Liquid Metal Droplets via Asymmetric Microwall Arrays

Abstract

Abstract Eutectic gallium indium liquid metal (LM) is a promising conductive liquid for various electronic applications. In particular, the directional transport of LM droplets has potential applications in soft electronics to control electrical conductivity. Existing methods transport LM droplets by applying an electric field to generate an interfacial tension difference within the LM droplet due to nonuniform ionic distribution of the electrical double layer. However, these methods require confined channels and tethered systems to apply the electric field. In this study, channel‐free wireless transport of LM droplets is demonstrated via on‐demand magnetomechanical actuation of asymmetric microwall arrays comprising vertically aligned ferromagnetic iron particles embedded in polydimethylsiloxane. Asymmetric microwall of two different widths is designed to generate an asymmetric bending stiffness at a given magnetic field. The asymmetric microwall bends gradually in response to a linear external magnetic field perpendicular to the alignment axis of the iron particles. Therefore, nonuniform magnetomechanical bending induces a local height gradient along the microwall, causing gravitational‐force‐driven roll‐off motion of the LM droplet. Transport direction of LM droplet is modulated by varying the geometric parameters. Finally, the opposite‐directional transport of two LM droplets is demonstrated under a linear magnetic field by pre‐programming the asymmetric bending direction of each microwall array.

Keywords

• EGaIn
• liquid metal
• magnetic composites
• microarray
• polydimethylsiloxane