Strain sensing capabilities of Ag-sandwiched ITO as transparent thin film resistor

Abstract

Abstract Strain sensors with good sensitivity and high optical transparency are of notable use in smart and transparent electronics which demands opto-electromechanical application. In this work, strain sensing capabilities of thin film resistor with high optical transparency is evaluated. Transparent Thin Film Resistor (TFR) was prepared by sputtering trilayer of Indium Tin Oxide (ITO) and Silver (Ag) on flexible polyethylene terephthalete (PET) substrate. ITO thin film was optimized to achieve resistivity of ∼5.5 × 10−4 Ω.cm with ∼91% optical transmission in visible wavelength. Insertion of thin silver film (∼10 nm) between ITO films by sputtering at room temperature produced film resistivity ∼6 × 10−5 Ω.cm and resistance ∼4 K.Ω to serve as strain sensing layer. Longitudinal piezoresistive response was evaluated by cantilever beam bending method. Gauge factor of 3.5 ±0.3 and optical transmission of ∼87% in 400-800 nm wavelengths (visible region) was measured on the transparent TFR. Piezoresistive response was linear and reproducible with minimal hysteresis for strains up to 280 μƐ for the measurements carried out at ambient conditions.