# Synergy of a Complimentary Ionic Biogel Network for Through-Hair Neurohaptics

## TL;DR

A new ionic biogel enables non-invasive through-hair neural recordings by combining multiple useful properties in one material.

## Contribution

A membraneless, organelle-inspired ionic biogel is introduced with synergistic thermoreversible, semiconducting, and bioadhesive properties.

## Key findings

- The biogel enables phase-reversible transistors with high transconductance of 44 mS at 40°C.
- It allows analysis of frequency-dependent neural responses over days, mimicking mechanoreceptor behavior.
- The material exhibits self-healing, electrochemical stability, and p-type semiconductivity.

## Abstract

Understanding the neural mechanisms underlying haptic sensations is crucial for advancing neuroprosthetics. However, achieving on-site amplification non-invasively through-hair neural recordings remains a significant challenge as it requires thermoreversible, bioadhesive, and semiconducting characteristics in the same material. Typical polymer composite compromises on complementary properties. To address this, we present a membraneless organelles - inspired ionic biogel that leverages liquid–liquid phase separation. This enables a unique synergy of complementary properties, including rapid thermoreversible transitions, p-type semiconductivity, thermoelectricity, enhanced electrochemical stability, self-healing, and bioadhesive capabilities. These characteristics enable to analyze the frequency dependence of event-related desynchronization during electrical stimulation over days mimicking the frequency response of mechanoreceptors sensation. This thermoresponsive, semiconducting ionic biogel also enables a phase-reversible, self-balancing, tip-shaped vertical organic electrochemical transistor with a high transconductance of 44 mS at 40°C. The ionic biogel demonstrates synergistic complementary properties to understand through-hair neurohaptics.