Microcrystalline silicon gauges on flexible substrates for high deformations with high spatial resolution

Microcrystalline silicon films are used as piezoresistive material to fabricate resistor and transistor strain gauges. Very small gauges are fabricated allowing the possibility to measure high deformations with both high sensitivity and spatial resolution. Resistor gauges with 5 × 125 μm² smallest size showed a gauge factor of -24 when applying high strains (0.55%, radius of curvature 5 mm). Field effect thin film transistor (TFT) gauges showed a gauge factor of -85 but under slightly lower strains (0.45%, radius of curvature 10 mm). This value is close to strain gauges made of single crystalline silicon (~100, regarding the absolute value), but which are not flexible and then cannot support high deformations. The more complex technological process of TFT gauges could reserve their use to the measurement of low deformations when high resolution is required, while resistor gauges could be chosen when focusing on a mix between size and sensitivity in a large range of deformations.