Soft piezoresistive sensor model and characterization with varying design parameters

Recent robots target safety, reconfigurability and interactivity by addressing the “softness” of the hardware either by endowing additional degrees-of-freedom or through inherent compliancy. These robots require distributed sensing with flexibility and softness that would not interfere with the robot's agility. There have been various sensing solutions using soft conductive materials including conductive silicone, liquid metal-filled micro-channels, and conductive-ink based sensors. However, we still lack a comprehensive study on their potentials, drawbacks, and the different parameters that affect their response. We present our design, fabrication process and characterization results for conductive silicone polymer and carbon ink-based curvature sensors. These sensors are flexible, mechanically robust under large strains, scalable, and easy to fabricate in large numbers. We propose an equivalent mechanical system to model sensors’ response. This model is unique for its extensive characterization of these polymer based sensors. Based on the characterization results, we systematically categorize and compare the performance of conductive silicone and carbon ink-based sensors with different design parameters.