A Soft Gripping Robot System with Graphene-based Piezoelectric Sensor (GPS)

Soft robots have been known for safer than rigid robots and being able to work closer with human and other surrounding objects, especially for having contact with delicate objects. One solution for delicate manipulation is to design flexible soft grippers with sensing capability and proper controllability. Adaptive control of soft gripping could be achieved with the sensing information between the gripper and the object. This paper presented a soft gripping robot system incorporate with Graphene-based Piezoelectric Sensor (GPS). The soft gripper was made of 3D printing (3DP) with the material of thermoplastic polyurethane (TPU). Six air chambers were made inside the soft gripper. The soft gripper was to be actuated by the inflation of these air chambers by pressurized air. The GPS was made of graphene and polyvinylidene fluoride (PVDF), which were initially well mixed in a solution and applied at the tip of the soft gripper. The layered structure of graphene allowed PVDF to have piezoelectric effect without the need of polarization. As the gripper tip had tactile contact with an object, the graphene/PVDF membrane slightly deformed and produced electricity. A mechatronic system was built to collect the piezoelectric signal. As a result, the gripping response was found to be linearly proportional to the applied pressure for pneumatic actuation. Furthermore, GPS was found to have around 6 times more sensitive than commercial PVDF sensor. The signal-to-noise (SNR) of GPS was around twice greater than commercial PVDF sensor. Therefore, the proposed soft gripper with GPS was suitable for gripping delicate objects and detection of small gripping responses at the gripper tip.