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

## TL;DR

This paper introduces a stretchable dielectric material for low-voltage neuromorphic transistors that can mimic synaptic functions and classify sounds with high accuracy.

## Contribution

The novel contribution is the development of a thiol–ene-cross-linked nitrile-butadiene rubber dielectric with superior synaptic and acoustic classification performance.

## Key findings

- The dielectric achieved a high dielectric constant (k = 14.6) and enabled low-voltage transistor operation (<5 V).
- Devices with multiple thiol cross-linkers showed enhanced hysteresis and synaptic behaviors.
- The transistor maintained excellent performance and acoustic classification accuracy (close to 99%) under 60% strain.

## Abstract

A stretchable, high-k 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 (k = 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.