Ultrasonic tactile sensor integrated with TFT array for force feedback and shape recognition

In this study, we propose an ultrasonic tactile sensor for real time contact force measurements and high-resolution shape recognition to enable safe and reliable robotic grasping of objects that may vary in compliance or texture. The sensing mechanism utilizes piezoelectric transduction where pulsed alternating voltage signals are applied to a polyvinylidene fluoride (PVDF) thin film, which generates pulses of ultrasound waves that travel upwards through the sensor components to the object contact interface. These waves are reflected back onto a receiver PVDF thin film that produces a localized voltage output, which is detected by the TFT (Thin-Film Transistor) array layer and converted into a two-dimensional grayscale image after signal processing. The ability of the tactile sensor to detect contact forces can be attributed to the sensor surface having a thin compliant polymer layer with a microstructure array. When the sensor contacts objects, the microstructures act as force concentrators, resulting in the localized deformation of the polymer layer that can be observed by the proposed ultrasonic imaging technique with an observed linear response to normal static forces in the range of 1-6 N. Furthermore, the shape sensing resolution and force detection range of the tactile sensor can be tuned by varying the number of microstructures in the array and the utilization of polymers with varying hardness, respectively.