1 Optical Bio Microsystems Laboratory, Micro-Nano-Bio Integration Center, Department of Mechanical, Industrial and Aerospace Engineering, Concordia University, Montreal, H3G 1M8 QC Canada.

The fabrication of conductive polymer composites (CPCs) using polydimethylsiloxane (PDMS) and poly(3,4-ethylene dioxythiophene): poly(4-styrene-sulfonate) (PEDOT: PSS) as a matrix with multi-walled carbon nanotubes (MWCNTs) and silver nanoparticles (AgNPs) as fillers was investigated to determine their potential for use in applications such as electromagnetic interference (EMI) shielding, sensors, and thermal switches/cut-offs. The effect of the fillers was investigated using MWCNTs of different sizes and including both MWCNTs and AgNPs at different ratios. Scanning electron microscopy (SEM) analyzed the morphology of the CPCs showed that the inclusion of AgNPs in the PDMS matrix resulted in a particle size gradient, with larger particles at the bottom of the CPC, although SEM confirmed that there was no separation between PDMS/AgNP and bulk PDMS. SEM of the PEDOT: PSS/MWCNT composites showed an anisotropic structure, with MWCNTs randomly oriented and dispersed throughout the polymer. Electrical characterization showed that the fabrication method and the MWCNT diameter and content affect the conductivity, with MWCNTs of smaller diameters at 45 wt% in CPCs synthesized using ultrasonication having the highest conductivity at 121.21 S/m. The analysis of CPCs synthesized with polyethylene glycol (PEG) and glycerol was also shown to be feasible and improved the flexibility of the composite, and resulted in a conductivity of 378.97 S/m, ~ 26% higher than that reported in the literature. Finally, thermal characterization showed that PDMS and PEDOT: PSS composites exhibit the thermoelectric (TE) effect, where a change in temperature creates an electric potential and vice versa, with the temperature of PDMS composites rising from room temperature (22?) to approximately 70? when a 5 V potential was applied. Under the same conditions, PDMS composites with 50 wt% MWCNTs rose from room temperature to 106?, while composites with 30 wt% MWCNTs only rose to 65?. and 50 wt% MWCNTs. The PEDOT: PSS/MWCNT composites also exhibited the TE effect, with the measured resistance varying with temperature. These results demonstrate that CPCs exhibit tunable properties that are suitable for use in various electrical applications.

Supplementary information: The online version contains supplementary material available at 10.1007/s44291-025-00136-0.