Fabrication of Hierarchically Micro- and Nano-structured Mold Surfaces Using Laser Ablation for Mass Production of Superhydrophobic Surfaces

Abstract

Many studies have examined the formation of surfaces with mixed patterns of micro- and nano-sized lotus leaves that have hydrophobic properties. In this study, micro- and nano-shapes such as lotus leaves were fabricated on a metal mold surface using laser ablation and ripple formation. A microstructure on the mold surface was replicated onto poly(dimethylsiloxane) (PDMS) using the polymer casting method to manufacture low-cost hydrophobic surfaces. A PDMS surface with micro- and nano-structures that were the inverse image of a lotus leaf showed hydrophobic characteristics (water contact angle: 157°). From these results, we deduced that portions of the microstructures were wet and that air gaps existed between the microstructures and the water drops. In this paper we suggest the possibility of the mass production of hydrophobic plastic surfaces and the development of a methodology for the hydrophobic texturing of various polymer surfaces, using the polymer casting method with laser-processed molds.

Fabrication of Micro/Nano Structures on Metals by Femtosecond Laser Micromachining

“…The theoretical beam diameter of a laser beam after passing through the focusing lens is calculated by the following equation [74,75]:…”

Investigating and understanding the effects of multiple femtosecond laser scans on the surface topography of stainless steel 304 and titanium

“…On the other hand, laserinduced surface structures that are formed under laser irradiation have feature sizes smaller than the effective beam diameter, and the latter has been the subject of extensive research in recent years. Laser-induced structures that have been discovered on metals include laser-induced periodic surface structures (LIPSS) [4][5][6], bumps/cones [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], holes [7,9,17,18,23], undulating grooves [7,9,17], melt-like [18,24], and chaotic structures [7,9,25]. These laser-induced structures can be used to alter the wettability of a material, resulting in a more hydrophobic or hydrophilic surface [10,11,26].…”

“…They observed that when an irradiated area is rescanned multiple times at a particular experimental setting, the surface features become increasingly regular and well-defined. Similarly, Noh et al [13] fabricated highly regular arrays of bumps and pillars on NAK80 mold steel by repeating their laser scan thirty and fifty times, respectively. Kam et al [11] observed the formation of two distinct types of micro-cones on stainless steel 316L, which only appeared after the target was scanned more than one hundred times.…”

Comparison of bending fracture strength of silicon after ablation with nanosecond and picosecond lasers

“…Lasers with pulse durations ranging from a few picoseconds to femtosecond are currently under development; these lasers are referred to as ultra-short pulse lasers, and research using these lasers for laser ablation drilling has been conducted [12][13][14][15][16][17][18]. By using these lasers, the heataffected zone inevitably created during laser ablation can be reduced [19,20]. In TSV technology, it is crucial to minimize the heat-affected zone around the holes since the small cracks generated from this zone become larger, eventually damaging the circuit board [21].…”