Electromechanical Characterization of 3D Printable Conductive Elastomer for Soft Robotics

Soft, stretchable sensors, such as artificial skins or tactile sensors, are attractive for numerous soft robotic applications due to the low material compliance. Conductive polymers are a necessary component of many soft sensors, and this work presents the electromechanical characterization of 3D-printable conductive polymer composites. Dog-bone shaped samples were 3D printed using a digital light processing (DLP)-based 3D printer for characterization. The 3D printable resin consists of monomer, crosslinker, conductive nano-filler, and a photo-initiator. The characterization was performed in two tracks. First, the effect of two different crosslinkers was investigated with different compositions and second, the effect of concentration of conductive nano-fillers was explored. Crosslinkers were chosen by referring to previous studies, and carbon nanotubes (CNTs) were utilized as conductive nano-fillers. The samples were 3D printed and characterized using an electromechanical test setup. To demonstrate utility for 3D printed soft robotics, a capacitance-based joystick sensor composed of both conductive and non-conductive resins was 3D printed.

I. Introduction

Soft robotic systems enable compliant and dexterous mechanisms, which used to overcome numerous challenges seen in conventional rigid robots [1]. In most cases, fabrication of soft robotics still require numerous manual steps because of the difficulty in handling the elastomeric materials. One way to overcome this challenge is to use additive manufacturing techniques, commonly referred as 3D printing, for the fabrication of soft robots [2], [3], [4]. 3D printing can integrate and automate multiple separate fabrication steps, starting from design to assembly [5], [6]. Furthermore, 3D printing can enable the fabrication of more complex geometries, which would be challenging to achieve using conventional fabrication methods like molding [7].