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.
Highlights
Printed electronics have evolved as one of the most promising technologies in recent years enabling the design of electronic components on diverse substrates in a much simpler and efficient way [1,2,3,4]
The cured PDMS substrate was cut into 50 × 22 mm2 size and ultra-violet (UV) ozone treated for 10 min using UV cleaner
In this paper we proposed an innovative approach for the design of flexible strain sensors using coplanar waveguide RF devices
Summary
Printed electronics have evolved as one of the most promising technologies in recent years enabling the design of electronic components on diverse substrates in a much simpler and efficient way [1,2,3,4]. These conductive nanocomposites behave like piezoresistive transducers, where change in the bulk resistance of conductive network is subject to the application of stress and strain variations [16]. PDMS properties are well suitable for the high frequency applications such as radiation based transducers including antennas for strain and temperature sensing purposes [23]. In our case the maximum change in resonance frequency was 180 MHz and change in the length was 2.5 mm which is 6.1% of the total length of the radiating patch From these values the sensitivity is calculated as 72 kHz/ μm simulated and measured 0.076 that has been repeatedly tested for more than 200 endurance cycles
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