Integrated Piezoresistivity and Frequency Modulation for High-Sensitivity Printed Capacitive Strain Sensing

Printed electronics technology, known for its cost-effectiveness and versatility, has been leveraged to create highly sensitive and flexible capacitive strain sensors capable of precise deformation measurement. In this work, we integrated the piezoresistivity of capacitor electrodes with the interrogation frequency to control and increase the sensitivity of low strain detection using low interrogation frequency. This analysis is based on the activation of the transmission line model under stretching that leads to a big variation in the effective capacitance at low frequencies with gauge factor (GF) factors varying from −8.3 at 5 kHz to −33.9 at 50 kHz at 2% strain. Our findings offer valuable insights for designing capacitive strain sensors that operate on alternating current (AC) measurements. Increasing sensitivity while narrowing the required operating frequency range significantly reduces power consumption compared to working at high frequencies and elevates measurement accuracy.