# Electro-Mechanical Properties of Metallized Sodium Alginate Foils at the Limit of the Electrical Conduction

## TL;DR

This paper explores the electrical and mechanical behavior of gold-coated sodium alginate foils for use in eco-friendly electronic devices.

## Contribution

The study reveals the anisotropic mechanical properties and reproducible electrical resistance changes under stress in metallized biopolymer substrates.

## Key findings

- The substrates show anisotropic Young modulus, being more stretchable in-plane.
- Electrical resistance variations are reproducible under applied stress in the elastic regime.
- Metal cluster composition and distribution were elucidated using microscopy and diffraction techniques.

## Abstract

In recent years, much attention has been given to biopolymers
and
renewable raw materials obtained from nature to find alternatives
to petroleum-based materials. In this context, we developed a free-standing
and flexible conductive substrate by sputtering a thin layer of gold
onto a foil of sodium alginate, producing conductive self-standing
substrates. These substrates have been utilized for the fabrication
of eco-designed solution-processed optoelectronic devices. Herein,
we report experimental work to study the mechanism behind the dependence
of electrical resistance on the mechanical deformation. Data obtained
from mechanical measurements, such as strain, stress, deformation,
and bending, are correlated with morphological (Atomic Force Microscopy
and Transmission Electron Microscopy) and structural (X-ray Diffraction)
data relative to both the surface and the subsurface regions of the
metallized substrates. Collectively, these data enabled the elucidation
of both the composition and spatial distribution of the metal clusters
implanted within the polymer matrix. The substrates present an anisotropic
Young modulus, making them more stretchable in-plane with respect
to out-of-plane. In the elastic regime, the reproducibility of the
electrical resistance variations with respect to the stress applied
makes these substrates robust candidates for the realization of strain
sensors.