Screen-Printed Strain Gauge for Micro-Strain Detection Applications

A printed strain gauge based on metal/non-metal composite was successfully fabricated and tested for micro-strain ( $\mu \varepsilon $ ) detection. A silver ink was blended with a carbon ink to achieve a silver-carbon (Ag/C) composite ink. The composite ink was then screen printed on a polyimide substrate in a meandering pattern to achieve a desired resistance of $\sim 350~\Omega $ . The printed strain gauge was bonded on to a flat aluminum beam. The capability of the printed strain gauge to detect linear strain was investigated by applying varying tensile and compressive loads on the aluminum beam, to simulate $\mu \varepsilon $ . Corresponding linear gauge factors for tensile and compressive loads were calculated as 2.26 and 1.47, respectively. In addition, transverse gauge factors for tensile and compressive loads were calculated as 1.18 and 0.43, respectively. The strain gauge has a temperature coefficient resistance of 0.26%/°C. The screen-printed Ag/C composite strain gauge was also compared to a commercial strain gauge of similar gauge resistance. The results demonstrate that a strain gauge with screen-printed Ag/C and encapsulation ink on a polyimide substrate can be utilized for $\mu \varepsilon $ detection. The electromechanical response of the fabricated strain gauge as a function of resistance is investigated and presented in this paper.