Inkjet printed kirigami inspired split ring resonator for disposable, low cost strain sensor applications

The purpose of this study was to produce a kirigami inspired split ring resonator (SRR) strain sensor. Since the SRR resonance frequency depends strongly on its split gap, one kirigami cut was designed to align with the SRR split gap, allowing SRR resonance frequency to be varied by applying tensile stress. The relationship between frequency and induced strain helps to explain the strain sensing mechanism. Two sheets of paper were used as the dielectric for compatibility with the kirigami technique, and a conductive pattern was inkjet printed on the top paper using silver nanoparticle ink, whereas the ground plane on the bottom paper was inkjet printed using stretchable ink. The two papers were bonded using epoxy strain sensor and S parameters for the fabricated sensor were measured at different strain levels. Resonance frequency increased from 4 to 4.64 GHz for 17.24% applied strain, with measured strain sensitivity = 4.2 × 10⁷ Hz/% and minimum detectable strain level ≈0.84%. Measurement results were compared with simulation results. The proposed strain sensor is relatively easy to manufacture, low cost, and disposable because it was inkjet printed on paper. (paper)