# Electrospun Nanofibers for Integrated Sensing, Storage, and Computing Applications
## 3 Electrospun Nanofibers in Transistors: Computation and Multifunctional Electronics
### Advanced Electrospinning Methods for Transistor Production  
The study on the electrospun nanofiber transistors mainly focused on upgrading process technology to improve device characteristics, and impressive results have been achieved in the past few decades. The typical fabrication procedure of transistors with electrospun nanofiber semiconducting layer consists of solution preparation, fibers electrospinning, annealing and other treatments, electrode deposition, and final FET formation. Any details of these five steps directly impact the performance of the transistors, and thus great efforts have been made to adjust the process parameters to find the optimal ones. For the solution preparation part, either the concentration or the ratio of the targeted element would change the properties of the fabricated fibers according to transistor performance. The transfer characteristics of poly(stearyl acrylates)(PSA)/poly(3-hexylthiophene)(P3 HT) nanofiber-based FET for various blending ratios (Figure 10) were studied and most excellent electrical performance was obtained with 1:0.2 P3 HT/PSA mixture electrospun nanofibers of 3.21 \(\times\) 10\({}^{-2}\) cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\) mobility, which was two orders of magnitude more than that of pure P3 HT nanofibers (1.92 \(\times\) 10\({}^{-4}\) cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\)) due to the P3 HT edge-on orientation, and a more compact structure of P3 HT nanofibers were promoted by crystalline PSA to accelerate the transportation of the hole [69]. High-performance zinc tin oxide (ZnSnO) electrospun nanofibers with a variety of composition ratios were made [13], and optimized Zn\({}_{0.3}\)Sn\({}_{0.2}\)O nanofiber FET based on SiO\({}_{2}\) dielectric showed a high on/off current ratio (I\({}_{\text{on}}\)/I\({}_{\text{off}}\)) of 2 \(\times\) 10\({}^{7}\) and field-effect mobility (u\({}_{\text{FE}}\)) of 0.17 cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\) (Figure 11a-c). In addition, P3 HT nanofiber-based organic field-effect transistors produced by the coaxial electrospinning method were prepared, in which the P3 HT served as the core polymer and poly(methyl methacrylate) (PMMA) served as the shell polymer, followed by the extraction of PMMA(Figure 11g) [70]. Three types of solvent (chlorobenzene (CB), chloroform (CF), and 1,2,4-trichlorobenzene (TCB)) were used to pick the greatest one and CF was found to achieve nanofibers with the smallest fiber diameter, maximum FET mobility of 3.57 \(\times\) 10\({}^{-1}\) cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\), and strongest flexibility. The reason why CF stood out among those three solvents is that stretching of the P3 HT chain stretching along the long axis of the nanofiber during the electrospinning process was greatly promoted by a higher solubility in the chloroform system, which in turn enabled the formation of highly oriented crystalline grains after thermal annealing and resulted in an improvement of both the ductility of P3 HT nanofibers and the performance of P3 HT electrospun nanofiber-based transistors. As mentioned in the previous section, morphology and characteristics can be managed by changing the conditions of electrospinning. Aligned nanofibers were received by two parallel conducting Si strips as electrospinning collectors (Figure 11d), and corresponding transistors (Figure 11e) had greater mobility than disordered nanofiber-based FET, as shown in Figure 11f [71]. Besides, it was demonstrated that nanofiber networks with various channel coverage produced by altering the nanofiber collecting time during the electrospinning would affect the device performance. A higher density of nanofibers generally led to more conduct points for the carrier movement and thus larger on current (I\({}_{\text{on}}\)), higher field-effect mobility, and greater on/off current ratio. However, when the NiO network coverage hit about 85%, the device's current modulation capability deteriorated dramatically, with a tiny I\({}_{\text{on}}\)/I\({}_{\text{off}}\) ratio and a low u\({}_{\text{FE}}\) value.