Monolithic valves for microfluidic chips based on thermoresponsive polymer gels

Quanzhou Luo, Senol Mutlu, Yogesh B. Gianchandani, Frantisek Svec, Jean Frechet*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

103 Scopus citations

Abstract

The direct preparation of thermoresponsive monolithic copolymers by photopatterning of a liquid phase consisting of an aqueous solution of N-isopropylacrylamide, N-ethyl-acrylamide, N,N′-methylenebisacrylamide, and 4,4′-azobis(4-cyanovaleric acid) has been studied and the products used as valves within the channels of microfluidic devices. The volume change associated with the polymer phase transition at its lower critical solution temperature (LCST) leads to the rapid swelling and the deswelling of the 2.5% cross-linked monolithic gel thus enabling the polymer to close or open the channel and to function as a nonmechanically actuated valve. The LCST at which the valve switches was easily adjusted within a range of 35°C-74°C by varying the proportions of the monovinyl monomers in the polymerization mixture. The closed valve holds pressures of up to 18 MPa without noticeable dislocation, structural damage, or leakage. In contrast, following deswelling by raising the temperature above LCST the valve offers no appreciable flow resistance since its large, micrometer-size pores are open. Laser-triggered photobleaching of a fluorescent dye contained in the liquid phase enabled monitoring of flow through the device and determination of the times required to open and close the valve. The valves are characterized by very fast actuation times in a range of 1-4 s depending on the type of device. No changes in performance were observed even after repeated open-close cycling of the valves.

Original languageEnglish (US)
Pages (from-to)3694-3702
Number of pages9
JournalElectrophoresis
Volume24
Issue number21
DOIs
StatePublished - Nov 1 2003

Keywords

  • Lower critical solution temperature
  • Microfluidic device
  • Miniaturization
  • Monolith
  • Thermoresponsive polymer
  • Valve

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry

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