Design and microstructuring of PDMS surfaces for improved marine biofouling resistance

In this study room temperature vulcanized (RTV) silicone surfaces with desi gned surface microstructure and well-defined surface chemistry were prepare d. Their resistance to marine macrofouling by barnacles Balanns improvisus was tested in field experiments for deducing optimal surface topography dim ensions together with a better understanding of macrofouling mechanisms. Po lydimethylsiloxane (PDMS) surfaces were microstructured by casting the PDMS pre-polymer on microfabricated molds. The master molds were made by utiliz ing photolithography and anisotropic etching of monocrystalline silicon waf ers. Several iterative casting steps of PDMS and epoxy were used to produce large quantities of microstructured PDMS samples for field studies. The mi crostructured PDMS surface consisted of arrays of pyramids or riblets creat ing a surface arithmetic mean roughness ranging from 5 to 17 mum for differ ent microstructure sizes and geometries, as determined by scanning electron microscopy. Chemophysical properties of the microstructured films were inv estigated by electron spectroscopy for chemical analysis, time-of-flight se condary ion mass spectroscopy and dynamic contact angle measurements. Films were chemically homogeneous down to the submicron level. Hydrophobicity an d contact angle hysteresis increased with increased surface roughness. Fiel d tests on the west coast of Sweden revealed that the microstructure contai ning the largest riblets (profile height 69 mum) reduced the settling of ba rnacles by 67%, whereas the smallest pyramids had no significant influence on settling compared to smooth PDMS surfaces. The effect of dimensions and geometry of the surface microstructures on the B. improvisus larvae settlin g is discussed.