ZnO TFTs revealed as next-gen in-screen force sensors
Adding force sensing to capacitive touch screens gives many more features to a display, notably for stylus-based drawing applications or in gaming. Until now, adding 3D touch (touch location and force) meant additional processing electronics and sensing layers. But the researchers who leveraged the known piezoelectric properties of ZnO to create force sensing thin film transistors have now demonstrated that they could seamlessly integrate their force sensors onto the Indium gallium zinc oxide [IGZO] active matrix of most displays (the materials and deposition processes being similar). The force sensors can replace the capacitive sensing layer as a whole since each pressure sensor (transistor) also acts as a switch.
In a paper titled “Improved Performance of Zinc Oxide Thin Film Transistor Pressure Sensors and a Demonstration of a Commercial Chip Compatibility with the New Force Sensing Technology” published in the Journal of Advanced Materials Technologies, first author Siarhei Vishniakou describes how the ZnO TFTs’ piezoelectric characteristics and transistor performance had been optimized through oxygen-rich deposition conditions. For a 16×16 transparent pressure sensor array, the paper reports a sensitivity of 4nA kPa−1 and a latency below 1ms (an order of magnitude faster than today’s touchscreens response).
for testing with a display driver from Synaptics
Taking Apple’s 3D-Touch technology as a commercial benchmark, Vishniakou who founded the Californian startup Dimensional Touch and currently serves as its Chief Technology Officer observes that his technology could be implemented at a fraction of the cost of Apple’s 3D-Touch, without the 13 grams penalty noted for the iPhone 7. What’s more, the ZnO TFTs operate reliably even on thin flexible substrates. Although it has proven the new ZnO TFTs force sensors on a 1″x1″ device, the company is confident it can add its pixel-resolution force-sensing capability into any type of display from 5’’ diagonal to 27’’ diagonal and higher, using existing manufacturing equipment.
According to the researchers, cost would be on a par with the capacitive touchscreens it would replace in mass production.
Dimensional Touch – www.f6s.com/dimensionaltouch
UC San Diego – www.ucsd.edu
Related articles:
Graphene-based e-skin detects vibrations from audio to ultrasound
Active matrix sensor takes force input on touch-screen
See-through flexible e-skin is powered by underlying photovoltaics
Light nerves to equip soft robots
Self-powered transparent skin localizes touch
If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :
