# Electrospun Nanofibers for Integrated Sensing, Storage, and Computing Applications
## 5 Applications of Electrospinning in Sensors: Various Sensing Electronics
Copyright 2018 Elsevier B.V. (**g.h**) Piezoelectric sensors based on electrospun P(VDF-TFEF) with excellent flexibility: (**g**) SEM image of aligned nanofibers (scale bar, 10 \(\upmu\)m). (**h**) Picture of highly aligned piezoelectric fibers with free-standing condition (scale bar, 1 cm). Reprinted with permission from Reference [123]. Copyright 2013, Nature Publishing Group, a division of Macmillan Publishers Limited. as an electrochemical indicator [124]. Electrospinning technology was applied to prepare carboxylated multi-walled carbon nanotubes (MWNTs) doped nylon 6 (PA6) composite nanofibers (MWNTs-PA6) to serve as the backbone for pyrrole (Py) electropolymerization (Figure 18a,b). Reproductivity and specificity of the fabricated sensor were tested by investigation after 10 days of storage at 4 \({}^{\circ}\)C and further being hybridized with the target wtp53. Results showed that this sensor remained highly sensitive and provided a stable platform as an electrochemical DNA biosensor. For the application of electrospun nanofibers for gas sensors, a conductive polymer with inherent porous nature for the thorough absorption of gas molecules is better than inorganic materials. A novel approach for highly efficient conducting polymers-based gas sensors was proposed by the introduction of polymeric sensitizers (polymeric adsorbent) within the conducting polymeric nanostructures to form 1D polymeric adsorbent/conducting polymer core-shell nanocomposites via electrospinning and solution-phase polymerization [125]. It was possible to observe stable and distinct responses for this gas sensor, as shown in Figure 18c, and high sensitivity was exhibited when an extremely low concentration of NH\({}_{3}\) (20 ppb) stimulated the response as high as 3.8. Figure 18d shows that the response of SPEEK/PPy and PAN/PPy nanofibers increased rapidly under exposure to NH\({}_{3}\) and then gradually decreased when the gas was absent. It was also obvious that the PAN/PPy nanofiber-based sensors had a recovery time of less than 25 s, which is significantly smaller than that of SPEEK/PPy nanofibers (180 s). In summary, nanofibers prepared by the electrospinning technique always take a place in the applications of sensors for the fast and accurate detection of various signals, such as pressure, gas, chemical substances, biological materials, and so on, which mainly benefit from the universality of electrospinning based on solution preparation to produce the most variety of materials. Moreover, electrospun nanofibers with large specific surface area and porosity enable the exploration of e-skin and further research would prompt the  
Figure 18: SEM image of (**a**) MWNTs–PA6 composite nanofibers and (**b**) MWNTs–PA6–PPy electrode and the inset shows the partial surface morphology of the fibers. Reprinted with permission from Reference [124]. Copyright 2012 Elsevier B.V. (**c,d**) Conducting polymer-based gas sensors and the device response to gas: (**c**) Increase in gas response of SPEEK/PPy nanofibers in a progressive manner with a successive injection of NH\({}_{3}\) into the test chamber. The inset shows the response in the range of 20–500 ppb. (**d**) Response/recovery curves for SPEEK/PPy nanofibers at NH\({}_{3}\) concentrations of 500 ppm at room temperature. Reprinted with permission from Reference [125]. Copyright 2012 American Chemical Society. development of electrospun nanofiber-based sensors towards higher performance and more flexibility for wearable and functional systems.