A doubly cross-linked nano-adhesive for the reliable sealing of flexible microfluidic devices.

Along with the expansion of microfluidics into many areas of applications such as sensors, microreactors and analytical tools, many other materials besides poly(dimethylsiloxane) (PDMS) have been suggested such as poly(imide) (PI) or poly(ethylene terephthalate) (PET). However, the sealing methods for these materials are not reliable in that many of the methods are specific to the substrate materials. Here, we report a novel robust doubly cross-linked nano-adhesive (DCNA) for bonding of various heterogeneous substrates. By depositing 200 nm of epoxy-containing polymer, poly(glycidyl methacrylate), via initiated chemical vapour deposition (iCVD) onto various substrates and cross-linking them with ethylenediamine, a strong adhesion was obtained between the substrates. This adhesive system was not only able to bond various difficult-to-bond substrates, such as PET or PI, but it could also preserve the complicated morphology of the surfaces owing to the thin nature of the DCNA system. The DCNA allowed fabrication of microfluidic devices using both rigid substrates, such as silicon wafer and glass, and flexible substrates, such as PDMS, PET and PI. The burst pressure of the devices sealed with DCNA exceeded 2.5 MPa, with a maximum burst pressure of 11.7 MPa. Furthermore, the adhesive system demonstrated an exceptional chemical and thermal resistance. The adhesion strength of the adhesive sandwiched between glass substrates remained the same even after a 10 day exposure to strong organic solvents such as toluene, acetone, and tetrahydrofuran (THF). Also, exposure to 200 °C for 15 h was not able to damage the adhesion strength. Using the high adhesive strength and flexibility of DCNA, flexible microfluidic devices that can be completely folded or rolled without any delamination during the operation were fabricated. The DCNA bonding is highly versatile in the sealing of microfluidic systems, and is compatible with a wide selection of materials, including flexible and foldable substrates, even upon sealing few-μm-sized channels.

[1]  P. Selvaganapathy,et al.  Polyurethane-based microfluidic devices for blood contacting applications. , 2012, Lab on a chip.

[2]  Natasha Patrito,et al.  A novel metal-protected plasma treatment for the robust bonding of polydimethylsiloxane. , 2007, Lab on a chip.

[3]  K. Neoh,et al.  Plasma polymerization and deposition of glycidyl methacrylate on Si(100) surface for adhesion improvement with polyimide , 2001 .

[4]  D. DeVoe,et al.  Bonding of thermoplastic polymer microfluidics , 2009 .

[5]  A. Bhagat,et al.  Inertial microfluidics for continuous particle filtration and extraction , 2009 .

[6]  Ali Khademhosseini,et al.  Fabrication of non-biofouling polyethylene glycol micro- and nanochannels by ultraviolet-assisted irreversible sealing. , 2006, Lab on a chip.

[7]  K. Gleason,et al.  Solvent‐free modification of surfaces with polymers: The case for initiated and oxidative chemical vapor deposition (CVD) , 2011 .

[8]  David Beebe,et al.  Engineers are from PDMS-land, Biologists are from Polystyrenia. , 2012, Lab on a chip.

[9]  Sung Gap Im,et al.  Systematic control of the electrical conductivity of poly(3,4-ethylenedioxythiophene) via oxidative chemical vapor deposition , 2007 .

[10]  R. Tompkins,et al.  Continuous inertial focusing, ordering, and separation of particles in microchannels , 2007, Proceedings of the National Academy of Sciences.

[11]  C. Liu,et al.  Recent Developments in Polymer MEMS , 2007 .

[12]  H. Becker,et al.  Polymer microfluidic devices. , 2002, Talanta.

[13]  G. Whitesides,et al.  Solvent compatibility of poly(dimethylsiloxane)-based microfluidic devices. , 2003, Analytical chemistry.

[14]  S. Soper,et al.  Simple room temperature bonding of thermoplastics and poly(dimethylsiloxane). , 2011, Lab on a chip.

[15]  S. Baxamusa,et al.  Initiated and oxidative chemical vapor deposition: a scalable method for conformal and functional polymer films on real substrates. , 2009, Physical chemistry chemical physics : PCCP.

[16]  Lung-Ming Fu,et al.  Distillation and detection of SO2 using a microfluidic chip. , 2012, Lab on a chip.

[17]  J. Viovy,et al.  Fabrication of thermoplastics chips through lamination based techniques. , 2012, Lab on a chip.

[18]  P. Tabeling,et al.  Microfluidics and complex fluids. , 2011, Lab on a chip.

[19]  Nae Yoon Lee,et al.  A facile route for irreversible bonding of plastic-PDMS hybrid microdevices at room temperature. , 2010, Lab on a chip.

[20]  Karen K. Gleason,et al.  Initiated and Oxidative Chemical Vapor Deposition of Polymeric Thin Films: iCVD and oCVD , 2008 .

[21]  Daniel T Chiu,et al.  Disposable microfluidic substrates: transitioning from the research laboratory into the clinic. , 2011, Lab on a chip.

[22]  P. Hammond,et al.  Patterning nano-domains with orthogonal functionalities: Solventless synthesis of self-sorting surfaces , 2008, 2009 Optical Data Storage Topical Meeting.

[23]  Miles C. Barr,et al.  Chemical Vapor Deposition of Conformal, Functional, and Responsive Polymer Films , 2009, Advanced materials.

[24]  Paul Watts,et al.  The application of micro reactors for organic synthesis. , 2005, Chemical Society reviews.

[25]  H. Girault,et al.  Monolithic and flexible polyimide film microreactors for organic microchemical applications fabricated by laser ablation. , 2010, Angewandte Chemie.

[26]  G. Whitesides.  The origins and the future of microfluidics , 2006, Nature.

[27]  Johan Roeraade,et al.  Method for fabrication of microfluidic systems in glass , 1998 .

[28]  K. Suh,et al.  On the role of oxygen in fabricating microfluidic channels with ultraviolet curable materials. , 2008, Lab on a chip.

[29]  Jingjing Xu,et al.  Conformal, Amine-Functionalized Thin Films by Initiated Chemical Vapor Deposition (iCVD) for Hydrolytically Stable Microfluidic Devices , 2010 .

[30]  Frantisek Svec,et al.  Room-temperature bonding for plastic high-pressure microfluidic chips. , 2007, Analytical chemistry.

[31]  Dino Di Carlo,et al.  High-throughput size-based rare cell enrichment using microscale vortices. , 2011, Biomicrofluidics.

[32]  Sung Gap Im,et al.  A conformal nano-adhesive via initiated chemical vapor deposition for microfluidic devices. , 2009, Lab on a chip.

[33]  A. deMello.  Control and detection of chemical reactions in microfluidic systems , 2006, Nature.