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

Abstract

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 crosslinking 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 lubricantswollen elastomers for practical uses.

Adhesion of fluid infused silicone elastomer to glass

“…3,4,9 In addition, when the surface and bulk elastic stresses are comparable in an elastomer, elasto-capillarity also plays a significant role in determining the surface deformation and wetting of fluidinfused elastomers. [27][28][29][30] We expect surface energy, oil replenishment, and elasto-capillarity to be affected by the oil fraction and contribute to adhesion.…”

“…33,38,39 In addition, experiments have shown that upon deformation of the swollen elastomer, fluid from the bulk can get transferred to the interfacial region due to local stress gradients. 27,28,30 The oil pushed to the interface creates a four phase contact zone at the periphery of an indenter where the volume of fluid pushed out depends on indentation depth and compressibility. 30 How this dynamic relaxation processes affect adhesion for swollen PDMS remains to be investigated.…”

Impact of the Network Density of Rough Poly(dimethylsiloxane)-Model Systems on the Hydrophobicity Assessment and Dynamic Wetting Behavior

“…This will impact the dynamic wetting behavior, as the lubricating effect will get lost with time, and indeed, the pearling effect was lost for most materials after some time of continuous water flow. 29 Also, the droplet elongation, which was observed to depend on the vPDMS viscosity for the first droplets, did not differ any more after 10 min of continuous water droplet flow.…”

“…Based on a literature survey, the dynamic wetting behavior of elastomeric materials can be influenced by a variety of parameters, including surface roughness, the chemical heterogeneity of the materials, and the presence of low-molecular-weight compounds/oils on the surface or within the material (diffusion to the surface is possible) as well as the stiffness of the material. − …”

Temperature-dependent soft wetting on amorphous, uncrosslinked polymer surfaces

“…3,32 Aside from viscoelasticity, complexities in soft wetting arise when the elastomer is infused with a liquid, where phase separation is possible. [33][34][35] In such a case, which is common for elastomers with moduli of B100 kPa or less, both poroelastic and viscoelastic responses affect the wetting ridge dynamics. [36][37][38][39] Although many efforts have been placed on the physics of soft wetting, the majority of experiments have been conducted with crosslinked elastomers or thin polymer sheets.…”