Laser-assisted electrohydrodynamic printing of sub-microscale 3D conductive features on low-melting-point polymeric substrates

Electrohydrodynamic (EHD) printing stands as a promising and cost-effective method for crafting intricate metallic structures at the micro/nanoscale, boasting diverse applications. Yet, conventional EHD-printed features often require high-temperature sintering (120-400 °C) for conductivity, limiting their integration and application on most polymeric substrates with low melting points (<300 °C). Here, we introduce an innovative laser-assisted EHD printing technique, which selectively melts the as-printed gold nanoparticles and expels residual solvents and surfactants, without damaging the substrates. This enables damage-free fabrication of highly conductive sub-microscale 3D structures on polymeric substrates at ambient temperature. Our printed features, as small as 604 ± 27 nm, exhibit a low resistivity of 2.54 ± 0.38 × 10-7 Ω m. Furthermore, we demonstrate the versatility of this approach by printing complex patterns and multimaterial structures on various substrates, including PET and human hair. The technique represents a significant advancement in EHD printing of electronics, offering exceptional precision and conductivity across diverse substrates and opening avenues for a wide array of applications in flexible electronics, biosensors, wearable devices, and biomedical implants.