How Swelling, Cross-Linking, and Aging Affect Drop Pinning on Lubricant-Infused, Low Modulus Elastomers

Soft, slippery surfaces have gained increasing attention because of their wide range of potential applications, for example in biomaterials, self-cleaning, antifouling, liquid collection, and more. One approach to prepare a soft, slippery surface is by swelling a cross-linked polymer network with a lubricant. However, an understanding of how swelling and cross-linking relate to slippery properties is still underdeveloped for low modulus elastomers. We study when a water drop sticks or slides on a vertical, silicone oil-swollen polydimethylsiloxane (PDMS) elastomer as a function of the degree of cross-linking and the degree of swelling. Our results indicate that the critical water drop volume required for sliding is strongly controlled by the degree of swelling; higher swelling leads to lower critical drop volumes. In addition, we demonstrate that highly swollen surfaces, and not lightly swollen surfaces, recover their slippery behavior during an aging process after they are rinsed with water. This is likely associated with regeneration of an oil-layer on the surface coming from the bulk substrate, illustrating the durability of lubricant-swollen elastomers for practical uses.