# Flexible Conductive Paper-Based Sensors for On-Skin Electrophysiological Monitoring and Wearable Applications

## TL;DR

This paper introduces a flexible, conductive paper-based sensor that can be used for on-skin monitoring and wearable applications due to its mechanical strength and stability.

## Contribution

The novel contribution is a composite film made of PEDOT:PSS, CNF, and an ionic liquid, fabricated via a simple process for wearable bioelectronics.

## Key findings

- The composite film achieved a tensile strength of up to 335 MPa and 21% strain.
- It showed excellent electrical stability across humidity and temperature ranges.
- On-skin recordings from a rodent model demonstrated stable signal acquisition without irritation.

## Abstract

Flexible, skin-conformable electrodes require materials
that combine
mechanical robustness, environmental stability, high electrical performance,
and biocompatibility. Here, we present a flexible conductive composite
film composed of poly­(3,4-ethylenedioxythiophene):polystyrenesulfonate
(PEDOT:PSS), cellulose nanofibers (CNF), and the ionic liquid 1-ethyl-3-methylimidazolium
ethyl sulfate (EMIM ES). The composite is fabricated via a simple
aqueous blending and filtration process, yielding a free-standing
film with a robust fibrous microstructure. ATR-FTIR analysis confirms
the successful integration of all components, while SEM imaging reveals
a percolated nanofibrillar architecture that enhances interfacial
adhesion and structural integrity. Mechanical testing reveals a tensile
strength of up to 335 MPa, accompanied by a strain of 21%, attributed
to the increasing CNF content. Composite films with low CNF content
exhibit excellent electrical stability across humidity levels between
10% and 90% and temperatures of 15–55 °C, and maintain
electrochemical performance after 100,000 cycles of mechanical fatigue
testing. On-skin electrophysiological recordings from a rodent model
demonstrate stable signal acquisition without skin irritation, establishing
the hybrid films as a promising platform for soft, wearable bioelectronic
interfaces.