High-Resolution and High-Conductivity Electrodes via Two-Step Annealing-Enhanced Solvent-Free Patterning of Silver Nanoparticles

Patterning of silver nanoparticles (AgNPs) for high-resolution and high-conductivity electrodes is essential for high-performance flexible electronic devices. AgNPs with sinster-bridged conductive networks maintain high electrical conductivities even at fine features owing to their constant (i.e., size-independent) percolation threshold, thereby enabling the fabrication of high-resolution, high-conductivity electrodes. However, patterning AgNP electrodes with high density using a facile, high-quality, and highly efficient approach remains challenging. Therefore, this study developed two-step annealing-enhanced solvent-free patterning of AgNPs using a UV-curable pressure-sensitive adhesive (PSA) film. The first annealing induces interfacial fusion between the AgNPs and the poly(1,1,2,2-tetrafluoroethylene) (PTFE)-coated substrate, converting point contacts into surface contacts while increasing the electrical conductivity through metallic bonding via sinter bridge formation. The second annealing allows the prepolymer adhesive to infiltrate voids between annealed AgNPs, creating mechanical interlocking after UV curing that significantly increases the work of fracture of the composite. This approach enables the formation of AgNP patterns without residues or loss, achieving critical dimensions down to 10 µm with excellent pattern fidelity. Moreover, the developed patterning technique simultaneously creates complementary patterns on both rigid and flexible films in a single process. Consequently, this study demonstrates applicability to flexible electronic devices, such as flexible heaters and a capacitive sensor array.