Soft capacitive tactile sensing array with high-robustness for three-axis pressure measurement

Tactile sensing with capability to measure and differentiate synergistic normal and shear pressures real-timely is crucial for possible dexterous manipulation of objects in robotic applications. Here in this paper, the measuring principle, as well as fabrication and testing of a soft tactile sensing array for three-axis pressure measurement are proposed. It is enabled by a floating electrode structure rather than a typical electrode-dielectric-electrode sandwiched prototype that the interconnects and sensing electrodes are realized using flexible printed circuit (FPC) meanwhile the floating electrodes are easily fabricated on a soft polyethylene terephthalate (PET) film. The transformation of embedding fragile interconnects into soft PDMS sensor body under excessive bending and deformation to a FPC layer of increased robustness and less compression drastically reduce the possibility of loss of function, and guarantee the robustness of the designed tactile sensing array. Moreover, hierarchically porous PDMS composite as the dielectric inlaid between floating electrode layer and sensing electrode layer results in a soft tactile sensing array with enhanced sensitivity (0.04 kPa(-1) under normal pressure and 0.10 kPa(-1) under shear pressures), large pressure sensing range (>300 kPa under normal pressure and > 62 kPa under shear pressures), minimal hysteresis, excellent repeatability, and fast response time (less than 60 ms) attributing to the synergistic effect of uniformly distributed macro and micro pores. The constructed soft tactile sensing array would provide essential sensing feedback for controlling an artificial arm in various tasks, illustrating its great potential application in robotics.