Photo-responsive droplet manipulation slippery lubricant-infused porous surface with ultra-high durability

Abstract

Photo-responsive slippery lubricant-infused porous surface (SLIPS) for droplet manipulation is flexible, non-contact and non-destructive in droplet manipulation, which has promising applications in flexible robotics, microfluidics, biomedicine, and chemical analysis. However, the repeated manipulations for droplets of SLIPSs are quite limited in the works reported so far, the poor durability of droplet manipulation severely limits the practical application of the surfaces. In this paper, a Fe3O4-doped polydimethylsiloxane (PDMS)-based SLIPS is proposed and implemented to achieve ultra-high repeated droplet manipulation numbers under near-infrared ray (NIR) laser irradiation. Firstly, micron columnar array structure with micro-pits on the top side, as well as, a "wall" structure out of the array were designed on SLIPS to reserve the lubricant. Secondly, the prototype of the SLIPS was fabricated by a 3-step ultraviolet (UV) lithography, and subsequently immersed in silicone oil for more than 96 hours to obtain the ultra-high durability slippery lubricant-infused porous surface (UD-SLIPS). With a power of 25-85 mW NIR laser, the repeated manipulation of microdroplets (≤ 5 μL) in the scale of 1 cm can exceed more than 3000 times which is far beyond that in previous reports. Finally, the droplet manipulation performance of this photo-responsive UD-SLIPS and the influence of infusion time on durability were investigated. The mechanism of the PDMS "swelling" effect was found to be the key factor in improving the droplet manipulation durability of SLIPS. The findings of this work would be of great significance for the development of highly durable photo-responsive functional surfaces for droplet manipulation.