Superhydrophobic Micro/Nano Dual-Scale Structures

Abstract

In this paper, we present superhydrophobic micro/nano dual structures (MNDS). By KOH-etching of silicon, well-designed microstructures, including inverted pyramids and V-shape grooves, are first fabricated with certain geometry sizes. Nanostructures made of high-compact high-aspect-ratio nanopillars are then formed atop microstructures by an improved controllable deep reactive ion etching (DRIE) process without masks, thus forming MNDS. Resulting from both the minimized liquid-solid contact area and the fluorocarbon layer atop deposited during the DRIE process, the MNDS show a reliable superhydrophobicity. The contact angle and contact angle hysteresis are -165 degrees and less than 1 degrees, respectively. This superhydrophobicity of MNDS is very stable according to squeezing and dropping test, even in high voltage conditions with the electrowetting threshold voltage of -300 V. Therefore, this micro/nano dual-scale structure has strong potential applications to the self-cleaning surface and superhydrophobic micro/nano fluidics.

A review on plasma-assisted VLS synthesis of silicon nanowires and radial junction solar cells

“…The pyramids used in these structures have a base width of 2 μm and a height of 1.6 μm. The reflectivity of the SiNWA is lower than the pyramid array, in accordance with literature [24,25]. The pyramid structure behaves like a standard broadband absorber [26] as the pyramid geometry provides a continuous change in effective permittivity, and thus, tapers the impedance from that of free-space to bulk Si.…”

“…Successful hybrid textured silicon surfaces have been fabricated using a combination of an alkaline etch to form a random pyramid array, followed by reaction ion etching to form the nanowire array [24] as well as MACE etching [6,25,34,35]. Reflectivity of less than <3% in the wavelength range of 300-1000 nm have been reported from this texture.…”

A high-efficiency superhydrophobic plasma separator

“…50 Here, we sprayed a superhydrophobic coating on our plasma separator by using a commercially available “Neverwet™.” The spray-on “Neverwet™” contains organic solvent ( i.e. , acetone, xylene, liquefied petroleum gas) and silica.…”

Switchable wetting &amp; flexible SiC thin film with nanostructures

“…The internal stress of SiC film was reduced to below 10 MPa by the thermal annealing at 450 o C for 50min, as is shown in Figure 1 Then an improved DRIE process with passivation enhancement was utilized to fabricate high-dense SiC nanostructure surface. Compared with the standard Bosch DRIE process, the passivation step of the improved DRIE process we presented is enhanced by increasing the passivation gas flow and the time of passivation step [15][16][17][18]. Therefore, the polymer deposited on the horizontal surface by the passivation step cannot be removed completely by the next etching step, and the nanoscale polymer residues will form and protect the substrate.…”