**5.3. Functional nanofiber textiles**

A lot of functions have been realized or enhanced by the use of nanotechnology in traditional textile materials. Electrospun non-woven fabrics, are widely investigated as a functional layer on some traditional substrates because of its high specific surface area, high gas permeability, and softness. The most promising application is that of protective cloth [92]. In some cases, TiO2 [93], ZnO [94], or MOF [95] was added in the electrospun fiber or spun into core-shell nanofiber as a photocatalyst [93] or adsorbent to prevent the penetration of organic toxic gas or fluid and UV light. Some research used PP [96], PA66 [97], or PAN [98] to directly produce a non-woven layer on a substrate layer as a protective textile. Yan, Jian, and Zachariah [99] prepared non-woven, fabric-based thermite textiles and tested their reactive properties. He found that this material can yield up to a 1000 times increase in propagation rate compared to its micro-sized counterparts. Other applications of electrospun non-woven materials as a functional layer in textiles include full-color, light-emitting electrospun nanofiber [100] and energy harvesting and self-powered textiles [101].

These applications illustrate the bright future of electropsun non-woven fabrics in functional textiles, however, few industrial products have been pushed to market. More fundamental research work is still required to find out how to adhere non-woven fabrics to traditional textiles without influencing their properties [97]. Although mass production has been carried out by some companies, fewer examples have been revealed using functional materials.

## **5.4. Sensors**

Many kinds of materials such as polymers [102], semiconductors [103], and organic/inorganic composites [104] have been used as sensing materials to detect targeted toxic gases, toxic solid, or toxic fluid materials based on various sensing techniques and principles. Electrospun nonwoven fabrics have a specific surface approximately 1–2 orders of magnitude larger than flat films, making them excellent candidates for applications in ultrasensitive sensors. Different electrospun non-woven materials have been applied as ultrasensitive sensors to detect the signal changes of acoustic waves [105], resistivity [106], photoelectricity [107], optical waves [108], and amperometric parameters [109]. It was found that parameters including specific surface area, fiber diameter, and membrane thickness have great influence on the detecting properties of sensors. Higher surface-to-volume ratios of electrospun non-woven fabrics represents the key to guarantee fast and sensitive mass transport, electric charge transport, and signal-to-noise current ratios. Therefore, regulating the parameters of the electrospinning process or solution properties has been adopted to produce more porous fiber and even hollow fiber structures [110]. A thick membrane was found to own a larger sensing area and vacant volume into which more analytes could be absorbed and diffused [111]. However, more experimental studies and theoretical work is required in order to achieve a better control over the size and secondary structure of electrospun non-woven fabrics.
