Multi-material (fabric and thermoplastic) printed substrate for 4D applications

Abstract

In the past few years wearable gadgets have gained popularity among academics and industries. A lot of work has been focused on wearable sensors as accessories. Yet less work has been reported on the sensor directly incorporated into the clothes of the user. This study is an extension of the work reported on 3D printed thermoplastic polyurethane (TPU) on fabric as wearable smart sensors in which the 4D characteristics of the wearable sensor using fused filament fabrication (FFF) were reported. In the present work, the process capability of the FFF for printing the TPU on cotton lycra fabric for 4D characteristics was explored. The samples of TPU substrate (60×54×0.65mm) were printed on cotton lycra fabric and a ring resonator test was employed for all samples under unloaded and loaded (25N) conditions. The resonating frequencies were measured for two cycles of loading and unloading on a vector network analyzer (VNA). Further, the dielectric constant (εr) was calculated for all the samples under loading and unloading conditions. Finally, process capability was ascertained by calculating the process capability indices (Cp and Cpk) values for εr for loaded and unloaded conditions for each cycle of all samples.