Flexible double stage POSTFT based on Poly-Si technology for robotic skin application

In this work we present a flexible read-out circuit embedded with a POSTFT (Piezoeletric Oxide Semiconductor TFT) tactile sensor for electronic skin application. The circuit has been fabricated using n-mos LTPS (Low Temperature Poly-Silicon) technology, integrated on a flexible substrate of PI (PolyImide). A cascade of two common source amplifiers, engineered to provide enhanced output, composes the schematic. The tactile sensor has been designed adopting an extended gate configuration to provide higher robustness to the mechanical solicitations. The optimization of the piezoelectric properties of the device has been accomplished through a well-established poling procedure, reaching piezoelectric coefficient of 45 pC/N. Once fabricated, the sensor has been detached from the rigid carrier and bonded to a flexible PCB for testing purpose. A mini-shaker has been used to electromechanically stimulate the sensor and verify the performance, obtaining output signal up to 2.5Vp-p for a mechanical stimulus of 1N @200Hz.