Pressure Mapping With Piezoresistive Sensor on Oxide TFTs Backplane

We report a pixel circuit with a piezoresistive sensor using amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistor (TFT) backplane for large-area pressure mapping. The proposed pixel circuit consists of TFTs, piezoresistive sensor, and a capacitor. The pressure sensor shows a large resistance change between 1011 and 107 ohm. The RC charging time to the capacitance can be modulated by pressure-dependent resistance within pre-charging period for sensing. The pressure sensor array has a resolution of 0.625 mm, rising and falling times of
$40 ~\mu \text{s}$
and
$10 ~\mu \text{s}$
, respectively. The output voltage is between 0.15 V (zero pressure) and 1 V (2 kPa) without an external amplifier. We demonstrate the pressure mapping over
$32\times32$
active-matrix pressure sensor array.