Mechanical Properties of Individual Conductive Protein Nanowires and Their Percolation Behavior in Elastomer Nanocomposites †

Abstract

High-performance soft electronics require conductive fillers that balance functional electrical properties with mechanical compliance. This study investigates conductive protein nanowires (CPNs) from Geobacter sulfurreducens as a sustainable, mechanically compliant alternative filler in polydimethylsiloxane (PDMS)-based nanocomposites. The primary objective was to establish the fundamental mechanics of individual CPNs and characterize their integration into hydrophobic elastomers. Local nanomechanical characterization established the first experimental elastic modulus for individual CPNs at 1.3±0.1 GPa, validating their potential as compliant components compared to significantly stiffer synthetic alternatives. As incorporated into the archetype elastomer PDMS, nanocomposites were measured using amplitude modulation-frequency modulation bimodal imaging as a function of filler loading (wt%), revealing percolation behavior with a rheological threshold of 0.8 wt% and tunable stiffness in the low-MPa range. Additional electrical transport measurements as a function of filler loading yielded an electrical percolation threshold of 6.7 wt% for CPNs/PDMS. Template fabrication of CPNs/PDMS using anodic aluminum oxide (AAO) successfully lowered the electrical threshold to 0.1 wt% and demonstrated enhanced conductance in nanocomposites with nanochannel texturing. Overall, CPNs/PDMS nanocomposites exhibit tunable percolation thresholds that are further enhanced by confining in nanostructure to enable an effective soft electronics materials platform.