A microfluidic diluter based on pulse width flow modulation.
We demonstrate that pulse width flow modulation (PWFM) can be used to design fast, accurate, and precise multistage dilution modules for microfluidic devices. The PWFM stage unit presented here yields 10-fold dilution, but several PWFM stages can be connected in series to yield higher-order dilutions. We have combined two stages in a device thus capable of diluting up to 100-fold, and we have experimentally determined a set of rules that can be conveniently utilized to design multistage diluters. Microfabrication with resist-based molds yielded geometrical channel height variances of 7% (22.9(16) microm) with corresponding hydraulic resistance variances of approximately 20%. Pulsing frequencies, channel lengths, and flow pressures can be chosen within a wide range to establish the desired diluter properties. Finally, we illustrate the benefits of on-chip dilution in an example application where we investigate the effect of the Ca(2+) concentration on a phospholipid bilayer spreading from a membrane reservoir onto a SiO(2) surface. This is one of many possible applications where flexible concentration control is desirable.
Ainla
Alar
A
Department of Chemical and Biological Engineering, and Microtechnology Centre (MC2), Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
Gözen
Irep
I
Orwar
Owe
O
Jesorka
Aldo
A
D002118:Calcium / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D007201:Indicator Dilution Techniques / Q000295:instrumentation*; D008051:Lipid Bilayers / Q000378:metabolism; D044085:Microfluidics / Q000295:instrumentation* / Q000379:methods; D012822:Silicon Dioxide / Q000737:chemistry
D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D012822:Silicon Dioxide; D002118:Calcium