Additive manufacturing of flexible 3D surface electrodes for electrostatic adhesion control and smart robotic gripping

Abstract

Mechanically flexible surface structures with embedded conductive electrodes are attractive in contact-based devices, such as those used in reversible dry/adhesion and tactile sensing. Geometrical shapes of the surface structures strongly determine the contact behavior and therefore the resulting adhesion and sensing functionalities; however, available features are often restricted by fabrication techniques. Here, we additively manufacture elastomeric structure arrays with diverse angles, shapes, and sizes; this is followed by integration of conductive nanowire electrodes. The fabricated flexible three-dimensional (3D) surface electrodes are mechanically compliant and electrically conductive, providing multifunctional ability to sense touch and to switch adhesion via a combined effect of shear- and electro adhesives. We designed soft, anisotropic flexible structures to mimic the gecko's reversible adhesion, which is governed by van der Waals forces; we integrated nanowires to further manipulate the localized electric field among the adjacent flexible 3D surface electrodes to provide additional means to digitally tune the electrostatic attraction at the contact interface. In addition, the composite surface can sense the contact force via capacitive sensing. Using our flexible 3D surface electrodes, we demonstrate a complete soft gripper that can grasp diverse convex objects, including metal, ceramic, and plastic products, as well as fresh fruits, and that exhibits 72% greater electroadhesive gripping force when voltage is applied.