"Smart" polymeric microfluidics fabricated by plasma processing: controlled wetting, capillary filling and hydrophobic valving.

We demonstrate a mass-production-amenable technology for fabrication, surface modification and multifunction integration in polymeric microfluidic devices, namely direct lithography on the polymeric substrate followed by polymer plasma etching, and selective plasma deposition. We apply the plasma processing technology to fabricate polymeric microfluidics in poly(methyl methacrylate) (PMMA) and poly(ether ether ketone) (PEEK). First, deep anisotropic O(2) plasma etching is utilized to pattern the polymer via an in situ, highly etch-resistant, thin, Si-containing photoresist, or via a thick organic photoresist. Absolute control of surface roughness (from smooth to very rough), and the production of stable-in-time (slowly ageing) superhydrophilic microchannels are demonstrated. Second, we demonstrate the spontaneous capillary pumping through such rough, superhydrophilic plasma-etched microchannels in contrast to smooth ones, even 5 weeks after fabrication. Third, by using C(4)F(8) fluorocarbon plasma deposition through a stencil mask, we produce superhydrophobic patches inside the microchannels, and use them as passive valves. Our approach proposes "smart" multifunctional microfluidics fabricated by a plasma technology toolbox.

[1]  David B. Rhine,et al.  Fabrication of microfluidic devices in silicon and plastic using plasma etching , 2001 .

[2]  S. Mitra,et al.  Experimental and numerical investigation of capillary flow in SU8 and PDMS microchannels with integrated pillars , 2009 .

[3]  Frédéric Reymond,et al.  Polymer microfluidic chips for electrochemical and biochemical analyses , 2002, Electrophoresis.

[4]  J. McGettrick,et al.  Mimicking a Stenocara beetle's back for microcondensation using plasmachemical patterned superhydrophobic-superhydrophilic surfaces. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[5]  D. Ryu,et al.  Biomolecular engineering: a new frontier in biotechnology , 2000 .

[6]  Angeliki Tserepi,et al.  A low temperature surface modification assisted method for bonding plastic substrates , 2008 .

[7]  N. F. de Rooij,et al.  Microfluidics meets MEMS , 2003, Proc. IEEE.

[8]  Roger D Kamm,et al.  Nanointerstice-driven microflow. , 2009, Small.

[9]  J. C. Chen,et al.  Fast drop movements resulting from the phase change on a gradient surface. , 2001, Science.

[10]  Patterning of thick polymeric substrates for the fabrication of microfluidic devices , 2005 .

[11]  A. Cassie,et al.  Wettability of porous surfaces , 1944 .

[12]  Lloyd M. Smith,et al.  Hydrophilic/Hydrophobic Patterned Surfaces as Templates for DNA Arrays , 2000 .

[13]  Angeliki Tserepi,et al.  Plasma processing for polymeric microfluidics fabrication and surface modification: Effect of super-hydrophobic walls on electroosmotic flow , 2008 .

[14]  Lei Zhai,et al.  Patterned superhydrophobic surfaces: toward a synthetic mimic of the Namib Desert beetle. , 2006, Nano letters.

[15]  Che-Hsin Lin,et al.  Low azeotropic solvent for bonding of PMMA microfluidic devices , 2007 .

[16]  Hirotsugu Yasuda,et al.  Modification, degradation, and stability of polymeric surfaces treated with reactive plasmas , 2000 .

[17]  Nam-Trung Nguyen,et al.  Low-pressure, high-temperature thermal bonding of polymeric microfluidic devices and their applications for electrophoretic separation , 2006 .

[18]  Angeliki Tserepi,et al.  Nanotexturing of poly(dimethylsiloxane) in plasmas for creating robust super-hydrophobic surfaces , 2006 .

[19]  Angeliki Tserepi,et al.  Photosensitive poly(dimethylsiloxane) materials for microfluidic applications , 2007 .

[20]  E. Gogolides,et al.  Nano-textured polymer surfaces with controlled wetting and optical properties using plasma processing , 2009 .

[21]  Chong H. Ahn,et al.  Institute of Physics Publishing Journal of Micromechanics and Microengineering a Review of Microvalves , 2022 .

[22]  R. Kostiainen,et al.  Silicon micropillar array electrospray chip for drug and biomolecule analysis. , 2007, Rapid communications in mass spectrometry : RCM.

[23]  R. N. Wenzel.  RESISTANCE OF SOLID SURFACES TO WETTING BY WATER , 1936 .

[24]  Lei Zhai,et al.  Microfluidic valves based on superhydrophobic nanostructures and switchable thermosensitive surface for lab-on-a-chip (LOC) systems , 2008 .

[25]  Lei Zhai,et al.  Conformal switchable superhydrophobic/hydrophilic surfaces for microscale flow control , 2009 .

[26]  Angeliki Tserepi,et al.  Etching behavior of Si-containing polymers as resist materials for bilayer lithography: The case of poly-dimethyl siloxane , 2003 .

[27]  Frédéric Reymond,et al.  Plasma etched polymer microelectrochemical systems. , 2002, Lab on a chip.

[28]  Joël S. Rossier,et al.  Topography, Crystallinity and Wettability of Photoablated PET Surfaces , 1999 .

[29]  Plasma etching of thermoset polymer films for microchannels , 2006 .

[30]  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.

[31]  Osamu Tabata,et al.  High-performance genetic analysis on microfabricated capillary array electrophoresis plastic chips fabricated by injection molding. , 2005, Analytical chemistry.

[32]  K. Suh,et al.  Capillary kinetics of water in homogeneous, hydrophilic polymeric micro- to nanochannels. , 2007, Small.

[33]  S. Arscott,et al.  Microfluidic design rules for capillary slot-based electrospray sources , 2004 .

[34]  E. Gogolides,et al.  Tunable Poly(dimethylsiloxane) Topography in O2 or Ar Plasmas for Controlling Surface Wetting Properties and Their Ageing , 2007 .

[35]  E. Gogolides,et al.  Nanotextured super-hydrophobic transparent poly(methyl methacrylate) surfaces using high-density plasma processing , 2007 .

[36]  Armand Ajdari,et al.  Stable modification of PDMS surface properties by plasma polymerization: application to the formation of double emulsions in microfluidic systems. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[37]  Fredrik Nikolajeff,et al.  Instant oxidation of closed microchannels , 2007 .

[38]  Gary E. Wnek,et al.  Surface-Tension-Confined Microfluidics , 2002 .

[39]  E. Gogolides,et al.  Roughness Formation During Plasma Etching of Composite Materials: A Kinetic Monte Carlo Approach , 2007, IEEE Transactions on Plasma Science.

[40]  Klaus Kern,et al.  Vertical arrays of nanofluidic channels fabricated without nanolithography. , 2009, Lab on a chip.

[41]  Patrick Hunziker,et al.  Valves for autonomous capillary systems , 2008 .