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Micro-nano hybrid structures with manipulated wettability using a two-step silicon etching on a large area.

Kim BS, Shin S, Shin SJ, Kim KM, Cho HH - Nanoscale Res Lett (2011)

Bottom Line: The fabrication process is readily capable of producing MNHS covering a wafer-scale area.By controlling the removal of polymeric passivation layers deposited during silicon dry etching (Bosch process), we can control the geometries for the hierarchical structure with or without the thin hydrophobic barriers that affect surface wettability.MNHS without sidewalls exhibit superhydrophilic behavior with a contact angle under 10°, whereas those with sidewalls preserved by the passivation layer display more hydrophobic characteristics with a contact angle near 60°.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, Yonsei University, 262, Seongsanno, Seodaemun-gu, Seoul 120-749, Korea. hhcho@yonsei.ac.kr.

ABSTRACT
Nanoscale surface manipulation technique to control the surface roughness and the wettability is a challenging field for performance enhancement in boiling heat transfer. In this study, micro-nano hybrid structures (MNHS) with hierarchical geometries that lead to maximizing of surface area, roughness, and wettability are developed for the boiling applications. MNHS structures consist of micropillars or microcavities along with nanowires having the length to diameter ratio of about 100:1. MNHS is fabricated by a two-step silicon etching process, which are dry etching for micropattern and electroless silicon wet etching for nanowire synthesis. The fabrication process is readily capable of producing MNHS covering a wafer-scale area. By controlling the removal of polymeric passivation layers deposited during silicon dry etching (Bosch process), we can control the geometries for the hierarchical structure with or without the thin hydrophobic barriers that affect surface wettability. MNHS without sidewalls exhibit superhydrophilic behavior with a contact angle under 10°, whereas those with sidewalls preserved by the passivation layer display more hydrophobic characteristics with a contact angle near 60°.

No MeSH data available.


Related in: MedlinePlus

MNHS with micropillars fabricated with acetone-based PR stripping: (a, b) top-view images; (c, d) tilted-view images. The width of a square micropillar and the gap between pillars are 100 and 20 μm, respectively.
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Figure 3: MNHS with micropillars fabricated with acetone-based PR stripping: (a, b) top-view images; (c, d) tilted-view images. The width of a square micropillar and the gap between pillars are 100 and 20 μm, respectively.

Mentions: By sequentially using the DRIE technique for micropatterns and electroless etching of silicon for nanowires, we can hierarchically design MNHS with micropillars and nanowires. Figure 3 shows SEM images of the fabricated structures. Here, the width of a square micropillar and the gap between pillars are 100 and 20 μm, respectively. As can be seen from these figures, the nanowires were well synthesized over the entire area, including the tops of the pillars and the trench regions.


Micro-nano hybrid structures with manipulated wettability using a two-step silicon etching on a large area.

Kim BS, Shin S, Shin SJ, Kim KM, Cho HH - Nanoscale Res Lett (2011)

MNHS with micropillars fabricated with acetone-based PR stripping: (a, b) top-view images; (c, d) tilted-view images. The width of a square micropillar and the gap between pillars are 100 and 20 μm, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211421&req=5

Figure 3: MNHS with micropillars fabricated with acetone-based PR stripping: (a, b) top-view images; (c, d) tilted-view images. The width of a square micropillar and the gap between pillars are 100 and 20 μm, respectively.
Mentions: By sequentially using the DRIE technique for micropatterns and electroless etching of silicon for nanowires, we can hierarchically design MNHS with micropillars and nanowires. Figure 3 shows SEM images of the fabricated structures. Here, the width of a square micropillar and the gap between pillars are 100 and 20 μm, respectively. As can be seen from these figures, the nanowires were well synthesized over the entire area, including the tops of the pillars and the trench regions.

Bottom Line: The fabrication process is readily capable of producing MNHS covering a wafer-scale area.By controlling the removal of polymeric passivation layers deposited during silicon dry etching (Bosch process), we can control the geometries for the hierarchical structure with or without the thin hydrophobic barriers that affect surface wettability.MNHS without sidewalls exhibit superhydrophilic behavior with a contact angle under 10°, whereas those with sidewalls preserved by the passivation layer display more hydrophobic characteristics with a contact angle near 60°.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, Yonsei University, 262, Seongsanno, Seodaemun-gu, Seoul 120-749, Korea. hhcho@yonsei.ac.kr.

ABSTRACT
Nanoscale surface manipulation technique to control the surface roughness and the wettability is a challenging field for performance enhancement in boiling heat transfer. In this study, micro-nano hybrid structures (MNHS) with hierarchical geometries that lead to maximizing of surface area, roughness, and wettability are developed for the boiling applications. MNHS structures consist of micropillars or microcavities along with nanowires having the length to diameter ratio of about 100:1. MNHS is fabricated by a two-step silicon etching process, which are dry etching for micropattern and electroless silicon wet etching for nanowire synthesis. The fabrication process is readily capable of producing MNHS covering a wafer-scale area. By controlling the removal of polymeric passivation layers deposited during silicon dry etching (Bosch process), we can control the geometries for the hierarchical structure with or without the thin hydrophobic barriers that affect surface wettability. MNHS without sidewalls exhibit superhydrophilic behavior with a contact angle under 10°, whereas those with sidewalls preserved by the passivation layer display more hydrophobic characteristics with a contact angle near 60°.

No MeSH data available.


Related in: MedlinePlus