Flexible coplanar waveguide strain sensor based on printed silver nanocomposites

Abstract

This paper presents a robust approach towards the design and fabrication of a stretchable coplanar waveguide monopole strain sensor that measures the tensile strain through a linear shift in the resonance frequency unlike the conventional patch antennas strain sensors. The increment in physical length upon application of stretching force on the sensor results into lowering of the resonance frequency, which is correlated with tensile strain. Being a 2d structure, the sensor can easily be deployed on a planar surface to determine the tensile strain. Sensor parameters are optimized through simulations in high frequency structure simulator software. Silver nanowires (AgNWs) based solution is screen printed using a shadow mask on an elastomeric polydimethylsiloxane substrate. The operating frequency of the sensor is 2.49 GHz at ambient condition and it goes down to 2.31 GHz at 6.1% stretching. The simulated sensitivity of the sensor is 0.072 MHz/µm and measured sensitivity of 0.076 MHz/µm has been tested for more than 200 cycles, clearly illustrating the robustness of the proposed approach. These promising results show that this sensor can successfully be implemented for printed wearable applications targeted for monitoring of strain related activities.