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Letter
Droplet Motion Control on Dynamically Hydrophobic Patterned Surfaces as Multifunctional Liquid Manipulators Mizuki Tenjimbayashi, Masaki Higashi, Taku Yamazaki, Issei Takenaka, Takeshi Matsubayashi, Takeo Moriya, Masatsugu Komine, Ryohei Yoshikawa, Kengo Manabe, and Seimei Shiratori ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b01641 • Publication Date (Web): 14 Mar 2017 Downloaded from http://pubs.acs.org on March 17, 2017
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ACS Applied Materials & Interfaces
Droplet Motion Control on Dynamically Hydrophobic Patterned Surfaces as Multifunctional Liquid Manipulators Mizuki Tenjimbayashi†, Masaki Higashi†, Taku Yamazaki†, Issei Takenaka†, Takeshi Matsubayashi†, Takeo Moriya†, Masatsugu Komine†, Ryohei Yoshikawa†, Kengo Manabe†, and Seimei Shiratori†* †
Center for Material Design Science, School of Integrated Design Engineering, Keio University,
3-14-1 Hiyoshi, Yokohama, 223-8522, Japan. *E-mail:
[email protected] KEYWORDS: liquid manipulation; dynamic wettability; micro reactor; omniphobicity; sol-gel
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ABSTRACT In this letter, we introduce a novel liquid manipulation strategy to design dynamically hydrophobic and statically hydrophobic/hydrophilic patterned surfaces using an ‘omniphobicity’based technique. The surfaces guide the sliding direction of a droplet in the presence of a statically hydrophilic area where the droplet does not stick on the transport path significantly enhancing the fluidic system transport efficiency. The concept of dynamically hydrophobic and statically hydrophobic/hydrophilic patterned surfaces in conjunction with omniphobic patterning techniques having surface multi-functionality, we believe, has potential not only for fluidic applications but also for future material engineering development.
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ACS Applied Materials & Interfaces
Active surfaces having unique solid-liquid interactions are of both scientific and technological interest. In particular, anti-wetting surfaces that control liquid motion are attracting extensive attention because of their potential in industrial applications as fluidic devices, 1,2 and micro-reactors,3 in addition to fundamental studies in areas such as, liquid transportation,4,5 controlled deposition6 and as patterned devices.7,8 Such liquid manipulation techniques require composite hydrophobic/hydrophilic surfaces, where a patterned hydrophilic, high-adhesion area guides a droplet on a hydrophobic surface. Lai and co-workers reported a superhydrophobic/hydrophilic patterned surface with photocatalytic TiO2 nanotubes.9 Manna and Lynn designed slippery liquid-infused porous surfaces (SLIPS) with a hydrophilic sticky area.10 If applying hydrophobic/hydrophilic patterning surfaces to specific applications, for example, as the surface of a micro-reactor, then care must be taken to ensure that the surface can suitably guide a droplet over the hydrophobic area and to limit the contact of the droplet with the hydrophilic area so as not to decrease the transport efficiency.11 Furthermore, challenges remain to improve liquid manipulative surface properties such as, transparency and mechanical durability, in addition to developing new routes to identify facile fabrication methods.12–14 Recently, dynamically hydrophobic (dewet at low tilting angle: TA) surfaces have been introduced as third-generation anti-wetting surfaces, fabricated by covalently fixing flexible hydrophobic molecular chains on smooth surfaces to prevent the penetration of liquid into the coating.15–17 These surfaces have shown the possibility to design statically hydrophilic (static contact angle: SCA2R) F'( recovers because the droplet contact area becomes homogeneous again. The
graph in Figure 2 indicates that the F'( value can increase as a function of liquid volume and
the maximum F'( value in the range of 0
