Fabrication of nanostructured functional surfaces on polymer and silicon using self-assembly lithographic methods

We employed block copolymer nanolithography to fabricate transparent anti-fogging surfaces in poly(methyl methacrylate) (PMMA). The resulting surfaces comprised a dense array of hexagonally packed pillars of dimensions below the light diffraction limit, with pillar diameters (55±2) nm, pitch size of (73±1) nm, and height to diameter aspect ratio of about one.

The surface chemistry was tuned by treatment with low-pressure atmospheric Ar plasma to increase the surface free energy of PMMA from (44.8±0.8) mNm-1 to (53.7±0.5) mNm-1 and to, as a consequence, decrease the intrinsic Young contact angle from θγ=(68±2)°, for pristine PMMA samples, to below 50° for plasma treated samples.

This led to a superwetting and thereby an anti-fogging behavior of nanotextured PMMA surface. To confirm the anti-fogging effect over a large area, we present water vapour condensation performance over treated materials, conducted in the customized environmental chamber of controlled humidity and temperature.

While the Ar plasma induced superwetting property had a limited lifetime of about four hours, the thin layer deposition approaches were proposed, comprising coating by plasma assisted vapor deposition with inorganic SiOH-rich silica (SiOx) and high resolution sputtering with tungsten (W), separately.

This treatments enabled a considerably prolonged lifetime of the superwetting property of almost three months.