Fabrication of a strain sensor based on polymer/silver nanowires nanocomposite for medical applications: Siloxane based versus urethane based nanocomposites

Abstract

In the current study, strain sensors based on two polymer matrixes of polydimethylsiloxane (PDMS) and thermoplastic polyurethane (TPU) and conductive nanomaterials of the silver nanowires (AgNWs) were fabricated. The sensors were arranged with a sandwich like morphology in which AgNWs layer(s) were embedded with polymeric layers of PDMS or TPU. The effect of the polymer matrix type and the number of the conductive layers on sensor properties has been evaluated. Morphology and electromechanical properties of the sensors including electrical resistance (R), sensitivity of the resistance change to strain, linearity of the resistance change with strain and repeatability of the sensor response to cyclic loading were analyzed. The experimental results corroborated that with increasing conductive layers from one to three, the resistance decreased by 53% and 61% in respective PDMS and TPU based sensors. Moreover, the sensitivity decreased by 78% and 77% in PDMS and TPU based sensors, respectively. The calculation of the relative SD (RSD) of the maximum ΔR/R0 values substantiated that sensors were able to represent a repeatable response to the sequential loading/unloading cycles. The repeatability was decreased with increasing conductive layers from one to two, and then augmented with further increase in conductive layers. With respect to polymer type, the resistance and repeatability of the TPU based sensors was higher than the PDMS counterparts, whereas the sensitivity of the TPU based sensors was lower than the PDMS ones.