Si0_2-based variable microfluidic lenses fabricated by femtosecondlaser lithography-assisted micromachining

摘要

Si0_2-based variable microfluidic lenses were fabricated by femtosecond laser lithography-assisted micromachining(FLAM). Optofluidic devices have attracted much interest because the adaptive nature of liquids in microfluidics enablesunique optical performance that is not achievable within all solid state devices. SiO_2-based microfluidic devices are,particularly, attractive due to high transparency, physical and chemical stabilities. However, it is generally rather difficultto form the microstructures in microchannels because photolithography process is limited to planar substrates. In ourstudy, we fabricated SiO_2-based variable microfluidic lenses, which had micro-Fresnel lenses inside the channels, byusing FLAM, which was a combined process of nonlinear lithography and plasma etching. The resist patterns of theFresnel lenses were directly written inside chemically amplified negative-tone photoresist on SiO_2-based microchannelsof 250 im width and 6 im depth using femtosecond laser-induced nonlinear optical absorption. Following that, thepatterns were transferred to the bottom of the channels by using CHF_3and O_2mixed plasma. SiO_2-based Fresnel lenseswith smooth surface were formed on the bottoms. When the channel was filled with the air, the focal spot was observed2020 im from the lens surface. By injecting silicone oil into the channel, the incident light was switched to thedispersed.