High-loading homogeneous crosslinking enabled ultra-stable vertical organic electrochemical transistors for implantable neural interfaces

Organic electrochemical transistors (OECTs) with high transconductance, low driving voltage, and biocompatibility have emerged as dominant bioelectronics technologies. However, a significant challenge remains in achieving stable signal recording over extended durations, due to the restricted thermal and cycling stability. Here, by introducing a small molecular with double-end functionalized trifluoromethyl-substituted diazirine (DtFDA) as the crosslinker in the organic mixed ionic-electronic conductors (OMIECs), both p- and n-type vertical OECT (vOECT) achieves excellent thermal adaptability (> 100 °C), excepti°nal cycling stability (> 200,000 cycles), fast ion transporting capability (transient time < 1 ms), along with ultrahigh maximum transconductance (g_m) (> 0.34 S). The findings reveal that highly loaded crosslinkers (OMIEC:DtFDA = 1:1 in mass) triggered by ultraviolet can facilitate the formation of stable and homogeneous transistor channel, which holds lower crystallinity, wider d spacing, and face-on dominated packing, thereby leading to enhanced ion hydration/injection and decent carrier transport pathways. Moreover, in vivo brain recordings with stable signals were accessed from the developed ultraflexible vOECT even after a four-week interval, and the tissue biocompatibility was also validated by chronic epicortical implantation. This work signifies new possibilities for high-performance vOECTs with high fidelity signals recording under complicated operation environments, enabling broader implications for robust bioelectronics. © 2024 Elsevier Ltd