Ultrasonic tactile sensor integrated with TFT array for contact force measurements

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 an AC signal is applied to a polyvinylidene fluoride (PVDF) thin film to generate pulses of ultrasound waves that travel upwards through the sensor components to the contact interface while a receiver PVDF thin film detects the reflected waves and produces a localized voltage output that is detected by the TFT (Thin-Film Transistor) array layer. The ability of the tactile sensor to detect contact forces can be attributed to the sensor surface having a thin compliant PDMS layer with a microstructure array. When the sensor contacts objects, the microstructures act as force concentrators, resulting in the localized deformation of the PDMS layer and an observed linear response to normal static forces in the range of 1 to 6 N. The TFT array output after signal processing produces a two-dimensional grayscale image that enables not only high-resolution imaging but also contact force information for improved robotic grasping performance.