Capillarity-assisted fabrication of nanostructures using a less permeable mold for nanotribological applications

Abstract

A simple kinetic model is presented to describe the capillary rise of a thin polymer film into a less permeable polyurethane acrylate mold. In this model, capillarity is explained by the competition between capillary and hydrodynamic forces in the course of pattern formation. For a less permeable mold, it was found that the capillary rise increases linearly with time. In addition, the contribution of viscosity and film thickness disappears such that the kinetics is solely governed by the permeation kinetics and capillary force. The present model would be useful to describe the evolution of molded nanostructures when a less permeable mold material other than polydimethylsiloxane is used for the patterning. Moreover, nanostructures with different tip shapes ͑rounded or dimpled͒ were observed depending on the fabrication temperature. The structures were tested for potential nanotribological applications such as reduction in adhesive and friction forces.

Biomimetic patterned surfaces for controllable friction in micro- and nanoscale devices

“…When the holding temperature was raised to 150°C and maintained for 15 min, spherical patterns formed and further transformed into conical pillars with the increase of time to 30 min ( Figure 5C-D). Friction of these nano-patterns has been found to be much lower than that of the flat surface, being dependent on their size and shape [13,21]. The friction of nano-patterns can be further reduced by applying hydrophobic films such as self-assembled monolayers [22].…”

“…This soft lithography technique utilizes the competition between capillary and hydrodynamic forces in the course of pattern formation. Consequently, variation in size and shape of patterns can be achieved by adjusting the holding temperature and time via various dynamic motions of the polymer (e.g., meniscus rise and polymer reflow) [21]. Figure 5 shows some examples of nano-patterns with varying shapes and sizes fabricated by CFL [13,21].…”

“…However, two distinct and Polymer nano-patterns with different size and shape created using CFL by varying the holding temperature and time [13,21]. remarkable features of the replicated surfaces come into play in lowering the contact area, leading to lower μ values: (i) the distance between adjacent asperities is on a larger scale when compared to that of the nanopatterns and (ii) only those asperities that are high enough come in contact with the counter surface.…”

“…Consequently, variation in size and shape of patterns can be achieved by adjusting the holding temperature and time via various dynamic motions of the polymer (e.g., meniscus rise and polymer reflow) [21]. Figure 5 shows some examples of nano-patterns with varying shapes and sizes fabricated by CFL [13,21]. At the holding temperature of 120°C and time of 15 min, dimpled patterns initially formed as a result of meniscus formation, which evolved to dimpled pillars with the increase of process time to 30 min ( Figure 5A-B).…”

Mathematical Modeling of the Concentrated Energy Flow Effect on Metallic Materials

“…Numerous publications emphasize the interest of researchers in development of mathematical models describing nano-structures under the action of concentrated energy flows [29][30][31][32][33][34][35][36][37][38][39]. These models are based mainly on computer simulation of processes, going with the development of nano-structural states.…”