A Novel Parylene C Waveguide-Based High-Resolution Photonic Tactile Array Sensor

Recent advances in manufacturing technology and new material processes have enabled novel device designs. As the growing field of robotic tactile sensing calls for advanced tactile sensors, waveguide-based tactile sensors have shown promising mechanisms but system-level integrated solutions are needed to demonstrate their feasibility for sensor applications. In this work, a novel ultra-compact high-resolution tactile sensor based on asymmetric Mach-Zehnder interferometers (MZI) is proposed: PITS (Photonic Integrated Tactile Sensor). It is made from Parylene C waveguides using the Parylene photonic material platform. The sensor is composed of a 4 x 4 array of MZI sensing units and demonstrates multipoint contact sensing as well as shape detection with high sensitivity and low inter-unit crosstalk. The sensing unit is based on multimode interference mechanism explored with supplementary mechanical and optical simulation models. It demonstrates a 0.08 N dynamic range with <0.01 N force resolution, 7.59 signal-to-noise ratio and an average hysteresis of 7.7% over 10 repeated indents. The sensor is fabricated in two layers: a Parylene photonic layer and an align-bonded polydimethylsiloxane (PDMS) micropillar layer on top, which actuates the sensing units. This architecture features a design and fabrication pipeline that allows customizable sensitivity and dynamic range as well as scalable array designs.