# Thermal Radiation Sensors Based on Ionic‐Conducting Pectin Films

## TL;DR

This paper introduces improved pectin-based sensors that can detect non-contact temperature changes, advancing the development of electronic skins for human-robot interactions.

## Contribution

The study demonstrates enhanced stability and non-contact thermal sensing capabilities of pectin films using an AC configuration and protective coatings.

## Key findings

- Pectin film sensors with improved stability function continuously for multiple days.
- The sensors accurately detect non-contact temperature changes in ambient environments.
- The performance aligns with analytical models for radiative heat transfer.

## Abstract

Artificial electronic skins that mimic the properties and functionality of human skin are becoming increasingly important for human‐robot interactions. One ability of human skin yet to be thoroughly imitated in electronic skins is non‐contact temperature sensing. Imitating this property will be useful for creating novel touch‐free interfaces for human‐centered robotic systems. Ionic‐conducting sensing layers made from crosslinked pectin films have recently been found to exhibit extremely high contact temperature sensitivity, several orders of magnitude greater than traditional sensors. However, pectin film sensors suffer from large baseline conductance decays during prolonged measurements, and their non‐contact thermal radiation sensing capabilities have not yet been systematically investigated. Here, substantially improved thermal radiation iontronic sensing stability is first demonstrated by implementing an alternating current configuration with the pectin films. The performance of various polymeric coatings is additionally studied for preventing dehydration in pectin films to improve prolonged iontronic sensor performance. It is then shown that the pectin film sensors exhibit non‐contact temperature sensing response that closely match analytical models for radiative heat transfer rate. Altogether, the findings demonstrate clear advances toward non‐contact temperature‐based electronic skins and touch‐free interfaces from pectin or other ionic‐conducting films.

This work reports on ionic‐conducting thin‐film sensors made from crosslinked pectin for non‐contact perception via thermal radiation sensing. Pectin‐based sensors with improved robustness are demonstrated, exhibiting continuous functionality for multiple days rather than several hours. The improved pectin‐based arrays are then validated as thermal radiation sensors for non‐contact sensing of warm objects in ambient environments.