Chemiresistive and Chemicapacitive Devices Formed via Morphology Control of Electroconductive Bio-nanocomposites

Chemiresistive and chemicapacitive circuit elements are fashioned from polymer thin films that are bio-nanocomposites of polyaniline-chloride (PAn-Cl) nanofibers within a chitosan (CHI) matrix deposited on microfabricated electrodes (IAME-co-IME; 2 µm lines and 1 µm spacing). UV–vis spectroscopy of 0–100 wt% PAn-Cl/CHI confirms no electronic coupling between PAn and CHI. When aqueous dispersions of the bio-nanocomposite are slow dried or cast, frozen, and lyophilized, they produce dense (chemiresistive) or highly porous foam (chemicapacitive) membranes. Studied in air, deionized water, and in physiological buffers (PBS and HEPES), four-band probe measurements of the ionic to polaronic conduction show a conductivity that is composition dependent with a percolation threshold of ≈30 wt%. Cyclic voltammetry reveals all compositions to be electroactive. Electrical impedance spectroscopy (EIS) shows that resistive and capacitive properties can be controlled by composition and morphology with 50–50 wt% being favored. EIS modeling confirms a modified Randles circuit of low chi-square values (<0.05) that appropriately models the chemiresistive and chemicapacitive properties. DC offset voltages can externally control the predominantly chemiresistive and chemicapacitive properties of the devices for biosensor and biocircuit applications.