On comparison of sensing capabilities of three-dimensional printed wearable sensors

As reported in the literature, several studies have been performed on the fabrication of wearable sensors using silver-ink screen printing or copper tape on a fabric. But hitherto little has been reported on the four-dimensional capabilities of such sensors fabricated using screen printing/copper tape. In this work, an interfacial layer of thermoplastic polyurethane was three-dimensional printed on the cotton (80%)-lycra (20%) woven fabric. The conductive layers of the sensor were made by screen printing using silver ink or copper tape pasted on fabric to develop two types of wearable sensors. To ascertain the four-dimensional capabilities, a 25 N tensile load as a stimulus was applied to the fabric-based sensor leading to warpage over the silver-ink screen printed surface and delamination of thermoplastic polyurethane from the fabric. The sensor developed as a microstrip patch antenna was designed for a resonance frequency (Rf) of 2.45 GHz. The specific absorption rate was calculated using a high-frequency structure simulator to be 1.383 W/kg for screen-printed microstrip patch antenna. The specific absorption rate value for copper-tape-based sensors was higher than permissible at 30.52 W/kg, so the patch design was altered (to get it within the range). Finally, the prepared functional sensor with screen-printed silver ink shows an Rf of 2.44 GHz in the industrial, scientific, and medical band, whereas the copper-tape-based sensor has an Rf of 3.04 GHz.