Gradient induced liquid motion on laser structured black Si surfaces

摘要

This letter reports on the femtosecond laser fabrication ofgradient-wettability micro/nano- patterns on Si surfaces. The dynamics ofdirectional droplet spreading on the surface tension gradients developed issystematically investigated and discussed. It is shown that microdroplets onthe patterned surfaces spread at a maximum speed of 505 mm/sec, that is thehighest velocity demonstrated so far for liquid spreading on a surface tensiongradient in ambient conditions. The application of the proposed laserpatterning technique for the precise fabrication of surface tension gradientsfor open microfluidic systems, liquid management in fuel cells and drugdelivery is envisaged.