A designable surface via the micro-molding process

Abstract

A rapid prototyping process was presented to fabricate a nylon honeycomb microstructure coated with parylene C. The surface structure was designed to obtain a hydrophobic surface using the volume of fluid (VOF) model. With the micro-molding technique, the contact angle of the polymer surface could be designed and fabricated by changing the different microstructure surface diesteel mold inserts. For the honeycomb (20 μm width and 60 μm depth) microcavity side wall, an average micro-molding filling percentage of 95% could be achieved by using a three-section constant-pressure molding process. The solid surface wettability is governed by both the geometrical microstructures and the surface energy. A 2 μm parylene C layer was deposited on the nylon honeycomb microsurface to reduce the surface energy. To design honeycomb structures with different microcavity densities, the contact angle of these artificial surfaces could change from 91°to 130°. From a comparison of the contact angle measurements with the different models, the honeycomb-structured microsurface could be described by the Cassie-Baxter model. The errors between the VOF simulation and the measured data were o 10%. The drag reduction performance of the honeycomb microplates was investigated in a water tunnel with a high Reynolds number (from 0.5 × 10 6 to 4.6 × 10 6 ). As a result, the honeycomb microplates showed a maximum drag reduction rate of 36 ± 0.6% in comparison with the bare plates in such turbulent flow. Benefiting from the replaceable mold insert, more designable microstructure polymer surfaces can be manufactured by this rapid prototyping technique.

Focus on Bioinspired Textured Surfaces toward Fluid Drag Reduction: Recent Progresses and Challenges

“…This rapid prototyping technology can make more designable microstructures on polymer surfaces. [ 176 ] Song et al fabricated microstructures on oxygen‐free copper and 304 stainless steel by imprinting. [ 177 ] Li et al manufactured nanoporous TiO 2 films with diverse pore sizes on smooth titanium foil by a two‐step anodic oxidation process.…”

“…The drag reduction effect of the specimens can be obtained by comparing the results. [176,205] Toloui et al observed and analyzed the turbulent flow and roughness deformation around a rigid and flexible cylinder microstructure by digital inline holographic particle tracking velocimetry (DIH-PTV). [206] Utilizing high-resolution PIV measurement combined with refractive-index matching (RIM) technique, not only was the turbulence on a hemispherical array studied, but also the flow near a single roughness element was successfully observed.…”

Current Advances and Future Perspectives of Advanced Polymer Processing for Bone and Tissue Engineering: Morphological Control and Applications

“…The super hydrophobic or super hydrophilic design of micro surfaces can be well used in medical devices, especially the local microenvironment (topography and strength) can decisively affect the ability of cells to self-renew and differentiate ( Yatsushiro et al, 2016 ; Shiu et al, 2018 ). Wang et al ( Wang et al, 2018 ) fabricated honeycomb-like micro surface arrays with different contact angles by means of micro-injection ( Figure 6A ). Li et al ( Lee et al, 2019 ) successfully achieved the preparation of curved parts with sub-micron surface morphology through micro-injection and nano-imprinting ( Figure 6B ).…”

Thriving artificial underwater drag-reduction materials inspired from aquatic animals: progresses and challenges

“…Due to simple manufacturing and installation, coatings are widely applied to change the surface characteristics of materials. 29,166 Both the drag-reduction surface and the hydrophobic surface are based on the microstructure, and the combined effect of the two has been extensively researched and manufactured. Dou et al utilized the coating technology to create a bionic surface to reduce the drag.…”