Constructing conductive titanium carbide nanosheet (MXene) network on polyurethane/polyacrylonitrile fibre framework for flexible strain sensor

MXenes (two-dimensional early transition metal carbides and carbonitrides) possess both excellent conductivity and surface hydrophilicity, enabling more diverse potential applications. However, in flexible strain sensors, the flexible substrates are usually composed of hydrophobic elastomers such as thermoplastic polyurethane (TPU). To enhance the interactions between MXenes and hydrophobic. substrates, it is wiser to change the composition of the flexible substrate than to modify the surface of MXenes, so as to improve the interactions between the flexible substrate and MXenes without losing the excellent conductivity of MXene. We introduce polyacrylonitrile (PAN) into TPU, and then fabricate a flexible TPU/PAN mat through electrospinning. A highly conductive and stretchable Ti3C2 MXene/TPU/PAN mat was then prepared by a simple dip-coating process. The interaction mechanism between Ti3C2 MXene nanosheets and TPU/PAN mat was investigated by XPS and FT-IR. Finally, we build the MXene/TPU/PAN mat into a flexible strain sensor with excellent properties. By introducing PAN into flexible substrate, the interaction between Ti3C2 MXene and the flexible substrate was effectively improved without compromising Ti3C2 MXene's excellent conductivity. The MXene/TPU/PAN strain sensor possesses a wide sensing range (0–80%), a fast response (<140.6 ms), a low limit of detection (<0.1%), splendid coating adhesion and excellent durability (>1750 cycles). All of these properties are demanded in wearable electronics.