Castable three-dimensional stationary phase for electric field-driven applications
View Patent ↗A polymer material useful as the porous dielectric medium for microfluidic devices generally and electrokinetic pumps in particular. The polymer material is produced from an inverse (water-in-oil) emulsion that creates a 3-dimensional network characterized by small pores and high internal volume, characteristics that are particularly desirable for the dielectric medium for electrokinetic pumps. Further, the material can be cast-to-shape inside a microchannel. The use of bifunctional monomers provides for charge density within the polymer structure sufficient to support electroosmotic flow. The 3-dimensional polymeric material can also be covalently bound to the channel walls thereby making it suitable for high-pressure applications.
1. A process for producing a microfluidic device comprising a channel having a porous dielectric material disposed therein, wherein the porous dielectric material comprises a polymer material having an internal structure formed by a 3-dimensional network of struts, and incorporated charged sites and the generic formula
—(—(A) x —(B) y —(C) z —) q —
wherein, A, B, and C are monovinyl, polyvinyl, and bifunctional monomers, respectively and x, y, and z are greater than or equal to zero and can be equal or unequal, and q is greater than zero, the process comprising the steps of:
a) preparing a water-in-oil emulsion, comprising an oil phase and an aqueous phase wherein the oil phase contains a surfactant, a polymerization initiator, and one or more of the monomers selected from the group of monovinyl, polyvinyl or bifunctional monomers;
b) casting the emulsion into the channel;
c) polymerizing the monomers by optical initiation; and
d) exchanging the aqueous phase.
2. The process of claim 1 , wherein the polymerization initiator includes peroxides, persulfates, or azo compounds.
3. The process of claim 1 , wherein the step of exchanging includes electroosmotic flow.
4. The process of claim 1 , wherein the oil phase comprises about 11 wt % of the emulsion.
5. The process of claim 1 , wherein the monovinyl monomer is styrene, methacrylonitrile, acrylates, vinyl pyridine, or methacrylates.
6. The process of claim 1 , wherein the polyvinyl monomer is divinylbenzene, ethylene glycol dimethylacrylate, or trimethylolpropane trimethylacrylate.
7. The process of claim 1 , wherein the bifunctional monomers are trialkoxysilyl functionalized monomers, sulfonates, phosphonates, boronates, alkyl ammonium, or ammonium compounds containing active vinyl groups.
8. The process of claim 7 , wherein the bifunctional monomer includes trimethyloxysilylpropylmethacrylate, sodium vinyl sulfonate, vinyl phosphonic acid, or 4-vinyl phenylboronic acid.
9. The process of claim 1 , wherein the polymer material further includes acidic or basic functionalities.
10. The process of claim 9 , wherein the functionalities include vinyl pyridine or vinyl imidazole.
11. The process of claim 1 , further including the step of infusing a monomer mixture into the polymer material.
12. The process of claim 1 , wherein the microfluidic device is an electrokinetic pump.