Superhydrophobic, hierarchical, plasma-nanotextured polymeric microchannels sustaining high-pressure flows

We fabricated superhydrophilic and superhydrophobic polymeric microfluidic devices with controlled hierarchical, random roughness, using plasma processing. We implemented a dye staining technique to visually demonstrate the persistence of the superhydrophobic state under flow for pressures in excess of 2.5 bar inside the microchannel. We further confirmed the stability of superhydrophobicity by pressure drop measurements, friction factor and slip length calculations under laminar flow conditions. We also compared identical rough superhydrophilic and superhydrophobic microchannels showing reduced pressure drop in the latter by as much as 22 %. Plasma etching and simultaneous nanotexturing (followed by optional fluorocarbon plasma deposition) are thus shown as an easy-to-implement method for attaining robust Cassie-state against high-pressure microchannel flows.

[1]  Angeliki Tserepi,et al.  "Smart" polymeric microfluidics fabricated by plasma processing: controlled wetting, capillary filling and hydrophobic valving. , 2010, Lab on a chip.

[2]  A note on the effective slip properties for microchannel flows with ultrahydrophobic surfaces , 2006, physics/0611042.

[3]  Christophe Ybert,et al.  Achieving large slip with superhydrophobic surfaces: Scaling laws for generic geometries , 2007 .

[4]  Chiang Juay Teo,et al.  Analysis of Stokes flow in microchannels with superhydrophobic surfaces containing a periodic array of micro-grooves , 2009 .

[5]  Jens Harting,et al.  Simulation of fluid flow in hydrophobic rough microchannels , 2007, 0709.3966.

[6]  Chih-Ming Ho,et al.  Effective slip and friction reduction in nanograted superhydrophobic microchannels , 2006 .

[7]  Zhihong Zhao,et al.  Effects of hydraulic pressure on the stability and transition of wetting modes of superhydrophobic surfaces. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[8]  B. W. Webb,et al.  Liquid flow through microchannels with grooved walls under wetting and superhydrophobic conditions , 2009 .

[9]  Chang-Hwan Choi,et al.  Structured surfaces for a giant liquid slip. , 2008, Physical review letters.

[10]  B. W. Webb,et al.  Laminar flow in a microchannel with superhydrophobic walls exhibiting transverse ribs , 2006 .

[11]  A Tserepi,et al.  Mechanisms of oxygen plasma nanotexturing of organic polymer surfaces: from stable super hydrophilic to super hydrophobic surfaces. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[12]  B. Khoo,et al.  Flow past superhydrophobic surfaces containing longitudinal grooves: effects of interface curvature , 2010 .

[13]  Hans-Jürgen Butt,et al.  Boundary slip in Newtonian liquids: a review of experimental studies , 2005 .

[14]  P Tabeling,et al.  Slippage of water past superhydrophobic carbon nanotube forests in microchannels. , 2006, Physical review letters.

[15]  Howard A. Stone,et al.  Effective slip in pressure-driven Stokes flow , 2003, Journal of Fluid Mechanics.

[16]  B. Khoo,et al.  Microchannel flows with superhydrophobic surfaces: Effects of Reynolds number and pattern width to channel height ratio , 2009 .

[17]  Chang-Jin C J Kim,et al.  Influence of surface hierarchy of superhydrophobic surfaces on liquid slip. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[18]  James J. Feng,et al.  Enhanced slip on a patterned substrate due to depinning of contact line , 2009 .

[19]  Chang-Hwan Choi,et al.  Large slip of aqueous liquid flow over a nanoengineered superhydrophobic surface. , 2006, Physical review letters.

[20]  J. Rothstein,et al.  Direct velocity measurements of the flow past drag-reducing ultrahydrophobic surfaces , 2005 .

[21]  Dimitrios P. Papageorgiou,et al.  Hierarchical, Plasma Nanotextured, Robust Superamphiphobic Polymeric Surfaces Structurally Stabilized Through a Wetting–drying Cycle , 2012 .

[22]  J. Rothstein.  Slip on Superhydrophobic Surfaces , 2010 .

[23]  Neelesh Patankar,et al.  Design of surface hierarchy for extreme hydrophobicity. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[24]  Contact angle measurements on superhydrophobic carbon nanotube forests: Effect of fluid pressure , 2005, cond-mat/0505205.

[25]  Hoon Cheol Park,et al.  Direct measurement of slip flows in superhydrophobic microchannels with transverse grooves , 2008 .

[26]  Wouter van der Wijngaart,et al.  Sustained superhydrophobic friction reduction at high liquid pressures and large flows. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[27]  Chang-Jin Kim,et al.  Underwater restoration and retention of gases on superhydrophobic surfaces for drag reduction. , 2011, Physical review letters.

[28]  Andrea Mammoli,et al.  Drag reduction on a patterned superhydrophobic surface. , 2006, Physical review letters.

[29]  S. Seeger,et al.  Patterned superfunctional surfaces based on a silicone nanofilament coating. , 2008, Soft matter.

[30]  B. W. Webb,et al.  Laminar flow in a microchannel with hydrophobic surface patterned microribs oriented parallel to the flow direction , 2007 .