Polarizable Thiol–Ene Cross-Linked Nitrile Dielectrics for Stretchable Low-Voltage Neuromorphic Transistors with Acoustic Classification

A stretchable, high-<i>k</i> dielectric material based on thiol-ene-cross-linked nitrile-butadiene rubber (NBR) for synaptic transistors is demonstrated. We investigated NBR formulations cross-linked with three thiol cross-linkers. The thiol-ene-cross-linked NBR dielectrics achieve a high dielectric constant (<i>k</i> = 14.6), enabling low-voltage transistor operation (<5 V) and photopatterned capability. By comparing different thiol cross-linkers, we have found that more thiol groups facilitate higher charge mobility and larger hysteresis. The thiol-ene-cross-linked NBR dielectric-based transistor exhibited superior electrical properties, including a high mobility (0.42 cm² V^-1 s^-1), a high ON/OFF ratio (10⁴), and a small threshold voltage (0.2 ± 0.4 V). More importantly, these devices effectively mimic synaptic functions. A large hysteresis, driven by dielectric polarization and enhanced by thiol introduction, was observed, particularly pronounced in NBR dielectric with multiple thiol-cross-linkers. The thiol-ene-cross-linked NBR device displayed superior short-term plasticity and long-term potentiation/depression, indicating its learning and memory capabilities. Encouragingly, the fully stretchable NBR transistor maintained good electrical performance, stable hysteresis, and essential synaptic behaviors even at 60% strain. As a practical demonstration for neuromorphic applications, the thiol-ene-cross-linked NBR device exhibited excellent acoustic classification performance, achieving recognition accuracy close to 99% even under mechanical deformation. In summary, the developed thiol-ene cross-linked NBR offers highly promising electronic properties for stretchable, low-voltage neuromorphic devices.