Metastable and Electronically Percolating Silver Nanowire-Polymer Composites by Spray Drying

Silver nanowires (AgNWs) are extensively reported as 2D conductive composites for their neural metaplasticity mimicking behavior, crucial for next-generation computing. While 2D networks rely on junction-mediated ballistic transport, 3D AgNW bulk composites exhibit diffuse and percolation driven conduction. Comparing these systems could reveal key dimensional effects, though scaling the intricate 2D networks into the bulk remains challenging. We report a highly reproducible 3D metastable powder composite of anisotropic AgNW with poly(vinylpyrrolidone) as a supporting matrix, produced via spray drying. With rapid drying kinetics, affinity-driven anisotropic morphologies are observed with ellipsoidal microstructures bent at flexural angles. First-principles electronic percolation characterization of the compressed composite is determined by a four-point probe (4PP), and the percolative regimes are allotted. 2D AgNW networks reach ∼1-500 S/cm at network densities of ∼0.4-11 μm^-2. The 3D composites, on the other hand, span a wider range, from ∼10^-8 S/cm at 3 wt % to ∼10² S/cm at ∼90 wt % of AgNW loading. These values reflect the dominant conductive pathways within the interaction volume. Complementary electrochemical impedance spectroscopy confirms pressure-driven extremization in percolation, with conductivity rising by 2 orders of magnitude from ∼10^-2 to ∼1 S/cm at applied pressures of 0.3 to 50 MPa even for 10 wt % AgNW, where 4PP measurements show values near 10^-5 S/cm. Spray drying was chosen, as scalability was prioritized over nanoscale precision, making it suitable for bulk materials where microstructure control is secondary to throughput. Hence, the morphologically free AgNWs serve as a versatile precursor for industrially relevant down streaming and reprocessing. When the metastable composite was coextruded at high shear with a commercial elastomer, stretching induced alignment of the initially randomly oriented AgNWs was revealed by SEM micrographs.