On 3D printing of thermoplastic polyurethane over woven fabric for wearable sensors

ABSTRACTIn the past two decades several studies have been reported on thermoplastic-based 3D printed sensors. However, little has been reported on wearable sensors prepared by thermoplastic printing on woven fabric, especially for four-dimensional (4D) properties. This study reports the 3D printing of thermoplastic polyurethane (TPU) on woven fabric by using a fused filament fabrication (FFF) setup for the fabrication of wearable sensors. Further, rheological, mechanical, voltage resistance (V-R), radio frequency (RF), and 4D capabilities of the 3D printed substrate have been established. The 3D printing of TPU on woven fabric was performed at 225°C nozzle temperature with a printing speed of 21 mm/s, and infill density was kept at 80% and 100%. The RF characteristics were calculated using a vector network analyser (VNA) which suggests that there is no shift in resonating frequency (2.60 GHz at −81 dB) for ring resonator printed with 100% infill density (with an increase in strain value), whereas for 80% infill density sensor there was a notable shift in resonating frequency (from 2.82 GHz at −75 dB to 2.71 GHz at −76 dB) when the sensor was strained under load which further lead to a change in dielectric constant (εr) and loss tangent (tanδ).KEYWORDS: Fused filament fabricationsensormechanical strengthradio-frequency4D AcknowledgementsThe authors are thankful to the Department of Science and Technology (DST) (Government of India), for providing financial support (File no. SR/FST/COLLEGE/2020/997) and this research has been partially funded under NTU-PU collaborated project titled “Wearable 3D printed patch antenna”.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was supported by the Department of Science and Technology, Ministry of Science and Technology, India [SR/FST/COLLEGE/2020/997].