fig3

Figure 3. Electrolyte engineering of OECTs for electrophysiological recording. (A) Demonstration of wearable OECT array adopting solid gel electrolyte^[36]; (B) The SEM image of a SPE, showing porous structure. Scale bar, 200 μm^[41]; (C) Schematic of breathable skin-integrated electronics using an ultrathin hydrogel film as the skin/electronics interface^[42]; (D) Schematic of an internal IGT, which has mobile ions embedded in the active layer^[55]; (E) Schematic showing the cross-section of a vIGT. L denotes the vertical channel length. S, D, and G stand for the source and drain contacts and the gate electrode. The H-via shows a micro-conduit from the device surface through the ion membrane layer to permit hydration of the channel^[56]; (F) The time-frequency spectrogram of the neural data captured and wirelessly transmitted by a vIGT-based standalone device. The characteristic local field potential patterns associated with wakefulness, REM sleep, and non-REM sleep are revealed. A superimposed raw time trace highlights the theta oscillation characteristics during REM sleep. Scale bar, 250 ms; (G) Schematic of a biodegradable OECT based on biodegradable electrolyte^[39]. Figure 3A adapted with permission from ref.^[36], Copyright 2023 John Wiley and Sons; Figure 3B adapted with permission from ref.^[41], Copyright 2022 John Wiley and Sons; Figure 3C adapted with permission from ref.^[42], Copyright 2022 John Wiley and Sons; Figure 3D adapted with permission from ref.^[55], Copyright 2019 Authors, licensed under Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC); Figure 3E and F adapted with permission from ref.^[56], Copyright 2023 Authors, licensed under Creative Commons Attribution 4.0 International License; Figure 3G adapted with permission from ref.^[39], Copyright 2020 John Wiley and Sons. OECTs: Organic electrochemical transistors; SEM: scanning electron microscopy; SPE: solid-state polymer electrolyte; IGT: ion-gated electrochemical transistor; REM: rapid eye movement.