Design and microstructuring of PDMS surfaces for improved marine biofouling resistance

Abstract

In this study room temperature vulcanized (RTV) silicone surfaces with designed surface microstructure and well-defined surface chemistry were prepared. Their resistance to marine macrofouling by barnacles Balanus improvisus was tested in field experiments for deducing optimal surface topography dimensions together with a better understanding of macrofouling mechanisms. Polydimethylsiloxane (PDMS) surfaces were microstructured by casting the PDMS pre-polymer on microfabricated molds. The master molds were made by utilizing photolithography and anisotropic etching of monocrystalline silicon wafers. Several iterative casting steps of PDMS and epoxy were used to produce large quantities of microstructured PDMS samples for field studies. The microstructured PDMS surface consisted of arrays of pyramids or riblets creating a surface arithmetic mean roughness ranging from 5 to 17 microm for different microstructure sizes and geometries, as determined by scanning electron microscopy. Chemophysical properties of the microstructured films were investigated by electron spectroscopy for chemical analysis, time-of-flight secondary ion mass spectroscopy and dynamic contact angle measurements. Films were chemically homogeneous down to the submicron level. Hydrophobicity and contact angle hysteresis increased with increased surface roughness. Field tests on the west coast of Sweden revealed that the microstructure containing the largest riblets (profile height 69 microm) reduced the settling of barnacles 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 settling is discussed.

Antifouling properties of hydrogels

“…From the view of chemical composition, several hundred natural antifouling compounds have been found in marine organisms (seaweeds, sea squirts, etc) [2,3]. Researchers prepared an antifouling structure mimicking sharkskin [4,5], and some reports suggested that surface roughness plays important role in biofouling [6,7]. Compared to solid materials, the surface of most marine creatures is rather soft and contains much water.…”

Biomimetic materials with tailored surface micro‐architecture for prevention of marine biofouling

“…Masters were prepared according to methods described elsewhere. 7 In brief, a 5 ð 5 cm 2 area of thermally oxidized 3 inch Si(100) wafer was patterned with grooves using photolithography and anisotropic silicon etching in potassium hydroxide solution. Depending on the etching time, sharp or truncated V-shaped cross-sections of the grooves were achieved, which resulted in different relief structures of the moulded PDMS stamps.…”

“…The micro-architecture of the type created here (sharp ridges) has been shown previously to reduce the settling of barnacles by 67%. 7 The reason for selecting a micro-architecture with 60 µm wide ridges was to investigate the effect of the width of the line of SAMs on crystal formation.…”

“…5,6 Field tests on the west coast of Sweden showed that the microstructure containing the largest riblet profile height of 69 µm reduced the settlement of barnacles by 67%. 7,8 In order to screen the most effective dimensions of these topographic elements, pyramids and riblets have been produced in scales of 23-69 µm in height and 33-97 µm in periodicity. 7 In biological systems, advanced architectures are created with precise control of size and structure.…”

“…7,8 In order to screen the most effective dimensions of these topographic elements, pyramids and riblets have been produced in scales of 23-69 µm in height and 33-97 µm in periodicity. 7 In biological systems, advanced architectures are created with precise control of size and structure. In the marine environment, the majority of structured materials, such as shells (invertebrate exoskeletons), 9 are prepared by controlled biomineralization using calcium carbonate as the inorganic phase.…”