# Electrospun Nanofibers for Integrated Sensing, Storage, and Computing Applications
## 6 Artificial Synapses and Other Electronic Devices Prepared by Electrospinning
Ultralow power synaptic simulation through solid-ion gated organic field-effect transistors (OFETs) with a 3D interface conducting channel was realized in 2020 [128] and this single fiber field-effect transistor was made by the core-shell structure of PEO/PQT12 nanofiber joint with liquid electrolyte (PEDOT:PSS) as a gate dielectric. Figure 20a depicts a schematic picture of a biological synapse and PQT-12 fiber-based artificial synapse with a 3D ionic electrolyte as the transistor gate. The classic EPSC behavior of synaptic transistors induced by a presynaptic spike (\(-1\) V, \(0.1\) s) applied on the gate electrode can be seen in Figure 20b. Moreover, paired-pulse facilitation (PPF) was proven by applying two consecutive impulseswith a time interval of 0.2 s on the gate and the later EPSC was three times more than the former EPSC (Figure 20c). By changing the read voltage and amplitude of the pulse, minimum power consumption was calculated to be around 3.9 f per spike (Figure 20d,e), which was attributed to the large contacting interface area between the organic polymer and the solid ionic dielectric, offering a large number of ions to attach. Usually, the function of a high-pass filter can be realized by a synapse having a low probability of vesicle release in a biological neuromorphic network, which was also found for this single nanofiber FET with a gain of EPSC increasing from 1.2 to 6.6 when the frequency rising from 1 to 10 Hz (Figure 20f), reflecting the potential for this simple-fabricated device to realize the artificial synapse and further development in artificial intelligence and neuromorphic computing system applications. In 2021, organic electrochemical transistors with PEDOT:PSS/polyacrylamideamide (PAAm) nanofiber as channel layer took the stage for comprehensive neuromorphic computing and sensing platforms to monitor the biological signals in real-time (Figure 21a,b) [129]. In the whole electrical system, the added PAAm served as an ion-blocking layer to enable the device to have long-term plasticity and to avoid too much energy consumption, which would happen with only PEDOT:PSS material. Typical transient current response and long-term potentiation and depression (LTD) concerning pulse number are shown in Figure 21c,d. This FET exhibited an ultralow energy consumption of 113 fJ, as shown in Figure 21e. Originated from electrospun nanofibers, this transistor possessed tunable electrical conductance by controlling the density of fibers, and the variation for the EPSC could be three orders of magnitude with electrospun volumes ranging from 0.5 to 30 \(\mu\)L (Figure 21f). Further software simulation performance based on the array arrangement of FET devices offered possible chances toward smart platforms comprised of neuromorphic devices for interacting with biology. Figure 19: Schematic diagram of the excitatory postsynaptic current and the inhibitory postsynaptic current for different presynaptic impulses. **(a)** EPSC **(b)** IPSC. Reprinted with permission from Reference [126]. Copyright 2021 Chinese Physical Society. **(c)** Comparability between biological synapses and artificial synaptic transistors. Reprinted with permission from Reference [127]. Copyright 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Apart from the organic-fiber-based field-effect transistors, metal oxide semiconductor FET with electrospun nanofibers open a path for mimicking neural components, such as the ZnSnO nanofiber-based FET with ion-gel dielectric (Figure 21g,h) [130]. The amplitude of EPSC in this device rose linearly with the duration time and finally reached a saturating value of 71 nA (Figure 21i-j), and the shift in synaptic response generated by paired-pulse stimulation at the same intensity was referred to as PPF (Figure 21k). Moreover, this one-dimensional fiber-based FET was proven to mimic the high-pass dynamic filtering property when the amplitude of the EPSC increased from 40 nA to 76 nA with the changing of the spike frequency from 1 Hz to 100 Hz (Figure 21l).