Fabrication of Flexible Thin Films from Sodium Alginate Biopolymer Composites for Smart Wearable Sensors Targeting Respiratory Health

Abstract

Modern wearable sensors for health monitoring are becoming increasingly popular due to their versatility. This study investigates the effects of Co²⁺ ions in flexible alginate-based composite films with doped cobalt and poly(3,4-ethylene-dioxythiophene):polystyrenesulfonate (PEDOT:PSS) for respiratory health monitoring. Contrary to expectations, the Co²⁺-doped Na-Alg/PEDOT:PSS/Glycerol 3b nanocomposite showed lower LED intensity (168 ± 75 au) and conductivity (5.04 × 10^–5 S/m). The addition of Co²⁺ ions negatively affected the electrical performance and hindered the charge mobility and structural integrity. In contrast, the Na-Alg/PEDOT:PSS/glycerol 2b film achieved higher LED intensity (236 ± 25 au) and maximum conductivity (6.61 × 10^–5 S/m), which can be attributed to the plasticizing effect of glycerol that improves the homogeneity of the film and charge transport. This composite also shows excellent wearability on the skin, pressure sensitivity, and the ability to monitor respiration.