Electrically controlled microvalves to integrate microchip polymerase chain reaction and capillary electrophoresis

Abstract

Microvalves are key in realizing portable miniaturized diagnostic platforms. We present a scalable microvalve that integrates well with standard lab on a chip (LOC) implementations, yet which requires essentially no external infrastructure for its operation. This electrically controlled, phase-change microvalve is used to integrate genetic amplification and analysis via capillary electrophoresis--the basis of many diagnostics. The microvalve is actuated using a polymer (polyethylene glycol, PEG) that exhibits a large volumetric change between its solid and liquid phases. Both the phase change of the PEG and the genetic amplification via polymerase chain reaction (PCR) are thermally controlled using thin film resistive elements that are patterned using standard microfabrication methods. By contrast with many other valve technologies, these microvalves and their control interface scale down in size readily. The novelty here lies in the use of fully integrated microvalves that require only electrical connections to realize a portable and inexpensive genetic analysis platform.

Microvalves and Micropumps for BioMEMS

“…The valves can be actuated mechanically [1][2][3][4], pneumatically [5][6][7][8][9][10][11][12][13], electrokinetically [14][15][16][17], by phase changes [10,11,[18][19][20][21][22], or by introduction of external force [23,24]. Using the method of actuation as the differentiating parameter, five major classes of active microvalves can be identified in the literature: electrokinetic, pneumatic, pinch, phase change, and burst.…”

Optically addressable single-use microfluidic valves by laser printer lithography

“…External support equipment and reagents needed to operate fluidic devices also drive system costs and, often more importantly, they can severely limit functionality and portability. 2 In nearly all demonstrations of microfluidic systems to date, 2-9 microvalves-when they are included-have dictated to lesser or greater extent the microfabrication and assembly steps and have often impacted functionality, flexibility, complexity, and cost as well. Thermoplastic-based fluidic devices can be manufactured in large volumes at low cost through a diversity of well-established techniques, embossing and injection molding being the two most important.…”

“…[10][11][12][13] There have been a number of demonstrations of microfluidic systems in thermoplastics, 10,11,14,15 but these examples are a rarity compared to microfluidic devices based on PDMS and glass. 2,4,6,9,[16][17][18] Arguably, integrated microfluidic devices based on PDMS and glass [2][3][4]6,7,9 could be reconfigured as thermoplastic devices, but to date the examples of this are few, and researchers continue to actively seek ways to substitute PDMS for thermoplastics. [19][20][21][22] Our belief is that integrated microfluidic systems should be designed from the outset with consideration of batch fabrication, volume manufacture, and reproducibility, and that this naturally leads to a preference for thermoplastic components and structures.…”

“…[19][20][21][22] Our belief is that integrated microfluidic systems should be designed from the outset with consideration of batch fabrication, volume manufacture, and reproducibility, and that this naturally leads to a preference for thermoplastic components and structures. An important recent trend is to operate microfluidic devices with the most inexpensive supporting instrumentation feasible, 2,23 and this in turn has led to the "borrowing" of sophisticated but inexpensive consumer electronics technologies for lab-on-a-chip systems. For example, cell phones have been employed successfully to read the results of an assay run in a paper-based microfluidic device, 24 and "smartphones"…”

“…The microfluidic valve is a ubiquitous, core component of microfluidic systems [2][3][4][5][6][7][8][9]16,30 and its design, materials, and fabrication approach can greatly impact the cost-effective implementation of microfluidic systems. The microvalve controls fluid communication between fluidic elements such as microchannels, pumps, and reservoirs.…”