PVDF tactile sensors for detecting contact force and slip: A review

Tactile is defined as a continuous sensing of variable contact forces, heat transfer, slippage, and various stimuli producing pain. The contact force and slip are the primary information measured by tactile sensor. In this paper, a detailed review of the tactile sensors for detecting contact force and slip based on polyvinylidene fluoride (PVDF) piezoelectric films is presented. When a touch and relative motion occur between the sensor and an object, the PVDF film can induce an electrical field across its boundaries. Hence, the PVDF sensors are suitable for contact force and slip detection. In addition, the PVDF has numerous advantages especially the high sensitivity, large electro-mechanical transduction frequency bandwidth, high elastic permittivity, light weight and low cost. Therefore, the tactile sensor by PVDF can be developed as a versatile tool for automation applications such as the sensor systems of robotic gripper. The review describes specific information on the definition of piezoelectricity, the principle of piezoelectric signal by PVDF film, the structural design of various PVDF-based tactile sensors, the hardware and software design of tactile sensing system, as well as some typical applications of the PVDF tactile sensors in different electromechanical devices.