Selective laser sintering of silicon nanoparticles and silicon microparticles on flexible polymer substrates

This study demonstrates a nanosecond pulsed laser sintering method for fabricating flexible silicon-based patterns composed of silicon nanoparticles (SiNPs) and microparticles (SiMPs) on PET substrates. The ultrashort laser pulses induce localized photothermal heating, enabling surface melting and coalescence of SiNPs to form conductive networks without damaging the polymer substrate. By optimizing the SiMP-to-SiNP ratio, the lowest resistivity of 10 Ω·cm was achieved at 80 wt% SiMPs, significantly lower than the 26 Ω·cm of pure SiNP patterns. However, increased microparticle content introduced higher porosity and mechanical fragility. To address this, a secondary SiNP coating and sintering step was implemented, which filled interparticle voids, reduced surface roughness, and improved conductivity by an additional 12 %. The Si patterns exhibited stable, reversible resistivity between 22 °C and 110 °C, with a linear temperature coefficient of –0.5 Ω·cm/ °C, confirming their potential for flexible temperature sensing. Thermoelectric measurements showed that moderate porosity enhanced the Seebeck coefficient via energy filtering, while excessive porosity impaired grain connectivity. A maximum Seebeck coefficient of 82 μV/K was achieved at 80 wt% SiMP, measured at 50 °C. Bending tests indicated that high-SiMP patterns were prone to cracking, but the two-step sintering process improved mechanical robustness. These findings highlight a low-temperature, laser-based route for integrating silicon materials into flexible electronic systems.