Directly 3D-printed monolithic soft robotic gripper with liquid metal microchannels for tactile sensing

One of the most valuable contributions robotics can offer is support to daily human activities, yet rigid robots often fail to comply with safety regulations in the proximity of humans. Soft robotics takes inspiration from living organisms' ability to adapt to their environment using flexible structures. These systems have to generate mechanical forces and simultaneously sense their environment. We developed a soft gripper with integrated sensing microstructures by monolithically 3D printing the structure. The rubber gripper mimics the versatile sensing and actuation abilities of living organisms. This is done using stereolithographic printing technology, rubber material, and resistive, pressure sensitive EGaIn microchannels. Printed microscale pressure sensing cavities are filled with liquid metal and act as resistive pressure sensors. They imitate human haptic perception and provide a sensitivity of 0.5% kPa-1. Simultaneously, a soft-robotic actuator design, which is derived from pneumatic networks, delivers a force of 2.5 N with 16 kPa of actuating pressure and an average efficiency of 0.56 mW kPa-1. Monolithically 3D printed systems promise numerous advantages since the compliance matching between multi-modal capillary sensing networks and actuators enables scale production of smart soft manipulators. Potential applications include collaborative manufacturing and medical support systems such as exoskeletons.