Transparent, Antibiofouling\nWindow Obtained with Surface\nNanostructuring

Biofouling is one\nof the key factors which limits the long-term\nperformance of seawater sensors. Common measures to hinder biofouling\ninclude toxic paints, mechanical cleaning and UV radiation. All of\nthese measures have various limitations. A very attractive solution\nwould be to prevent biofilm formation by changing the surface structure\nof the sensor. This idea has been implemented successfully in various\nsettings, but little work has been done on structuring optically\ntransparent materials, which are often needed in sensor applications.\nIn order to achieve good antibiofouling properties and efficient optical\ntransparency, the structuring must be on the nanoscale. Here, we investigate\na transparent, antibiofouling surface obtained by patterning a semihexagonal\nnanohole structure on borosilicate glass. The nanoholes are approximately\n50 nm in diameter and 200 nm deep, and the interparticle distance\nis 135 nm, allowing the structure to be optically transparent. The\nantibiofouling properties of the surface were tested by exposing the\nsubstrates to the microalgae <i>Phaeodactylum tricornutum</i> for four different time intervals. This species was chosen because\nit is common in the Norwegian coastal waters. The tests were compared\nwith unstructured borosilicate glass substrates. The experiments show\nthat the nanostructured surface exhibits excellent antibiofouling\nproperties. We attribute this effect to the relative size between\nthe structure and the biofouling microorganism. Specifically, the\nsmall dimensions of the nanoholes, compared to the biofouling microorganism,\nmake it more difficult for the microalgae to attach. However, lubrication\nof the substrates with FC-70 perfluorocarbon resulted in contamination\nat a rate comparable to the reference substrate, possibly due to the\nchemical attractiveness of the alkane chains in FC-70 for the microalgae.