Electromechanical properties and physiological sensing enhancement of an in-situ assembled 3-D nanostructure: A comprehensive effect assessment of tannic acid treated 2-D Ti3C2Tx and 1-D graphene nanoribbon (GnR)

Abstract

Electrospun strain sensors allow facile integration with wearable devices, however, achieving high sensitivity and extended working range are often hindered by their non-homogenous, 2-dimensionally (2-D) responsive network and its instability under large stimuli. In this study, a novel strategy consisting of (i) nano-scale surface functionalization, materials formulations and (ii) micro-scale in-situ coating technique were employed to address these challenges. A nanohybrid sensor composed of 2-D tannic acid (TA) functionalized Ti3C2Tx MXene and 1-dimensional (1-D) graphene nanoribbons (GnRs) were developed taking advantage of the short response time from Ti3C2Tx and GnR's bridging effect and flexibility. TA functionalization helped increasing the electronegative surface terminations of Ti3C2Tx, enhancing the interfacial interaction between GnR and Ti3C2Tx and the integrity of the conductive network. The robustness and the interfacial stability of the responsive network was also promoted via a technique combining coaxial electrospinning with simultaneous electrospraying. The styrene-butadiene-styrene (SBS) nanofibers functionalized with electropositive cetryl ammonium bromide (CTAB) to provide electrostatic attraction for conformal coating of the electronegative nanohybrid onto the SBS platform. This, along with the synergism between 2-D Ti3C2Tx and 1-D GnR, led to in-situ formation of a 3-D responsive network. Also, a comprehensive assessment was conducted to study the effect of the additives' geometry on the electromechanical performance. The reported structure provided exceptionally high sensitivity (Gauge Factor (GF) of 2090 at 550%), excellent dynamic stability (enduring 5000 cyclic test under 100% strain), an extended working range (0.1%–550% strain) and fast response and recovery times (50, and 46 ms, respectively) at a low detection limit (0.1%).