Piezoelectric polymer oxide semiconductor field effect transistor (POSFET) devices for touch sensing

Abstract

-This work presents the POSFET based touch sensing devices and their experimental evaluation. POSFET touch sensing devices presented here are primarily developed for the robotic applications. The design of these devices is inspired from human sense of touch. These devices are implemented by spin coating thin (~2.5 µm) piezoelectric polymer (PVDF-TrFE) film, directly on to the gate area of MOS transistor. The polymer film is processed in situ. The POSFET device represents an integral "sensotronic" unit comprising of transducer and the transistor and are thus capable of 'sensing and processing at same site'. The POSFET touch sensing devices are tested in a wide range (0.15-5N) of dynamic normal forces and at different frequencies.

Response of P(VDF-TrFE) sensor to force and temperature

“…The change in sensor capacitance as a function of temperature (~ 7 pF/°C) for all three conditions studied is comparable with that of force (7.5 pF/N) for forces < 0.5 N. We therefore propose that this P(VDF-TrFE) tactile sensor could be explored for temperature sensing in addition to its current application for pressure/touch sensing [18]. Previously a p-n junction temperature diode was combined with POSFET to allow temperature monitoring [12].…”

“…The sensor capacitance shows a logarithmic dependence on applied force over the investigated force range up to 9 N. Forces below 0.5 N show a much greater sensitivity (~ 7.5 pF/N) than forces between 3 and 9 N (~ 0.26 pF/N). High sensitivity at the lower force range is important, as the majority of manipulative tasks carried out by a humanoid robot during day to day activities are in the region of < 1 N force [18].…”

“…978-1-4799-8229-5/15/$31.00 ©2015 IEEE Previously, P(VDF-TrFE) sensor was integrated with a CMOS field-effect transistor to create an all-encompassing sensing and in-situ processing device named piezoelectric oxide semiconductor field-effect transistor (POSFET) [18]. The POSFET features P(VDF-TrFE) layer directly deposited onto the transistor gate, which in turn controls the transistor drain current.…”

Novel Two-Dimensional Mechano-Electric Generators and Sensors Based on Transition Metal Dichalcogenides

“…The periodic time of our dynamic stress is 1ms. Therefore a proper assumption can be suggested that there is negligible delay between input force and output voltage phase 47 . Experimentally, the stress can be realized by bending the substrate periodically 26 .…”

P‐138: Rollable Multi‐Touch Organic Capacitive Pressure Sensor for Multi‐Directional User Interactions

“…To date, several types of pressure sensors, such as a resistive sensor with a metallic-particles-dispersed insulator [2], piezoelectric sensors [3,4], a strain gage sensor [5], and a selfcapacitive pressure sensor with a deformable insulator [6], have been developed. The resistive pressure sensor has a limitation in dynamic range and in the number of multi-point detections.…”