Figure 6: Transparent and light electronics for smart contact lens.
From: Wafer-scale design of lightweight and transparent electronics that wraps around hairs
(a) The membrane with on top transparent TFTs and gold strain gauge sensors is transferred on a plastic contact lens held between two fingers (scale bar, 2.5 mm). (b) The membrane transferred on an artificial eye. (c) Strain gauge sensor response to applied strain. The sensor can be potentially exploited to monitor the intraocular pressure. (d,e) Transparent TFT (W/L=280 μm/80 μm) measured on a contact lens placed on an artificial eye. The transfer characteristic refers to VDS=0.1 and 5 V while the output characteristic is for VGS from 2–5 V with a 0.5 V step. The transistor exhibits a mobility of about 7.2 cm2 V−1s−1, a threshold voltage of 0.34 V, a sub-threshold swing of 172 mV/dec, an on/off ratio greater than 105 and a transconductance of about 0.15 μS/μm at VGS=5 V.
