Integrated electrochemical velocimetry for microfluidic devices
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We present a new electrochemical velocimetry approach with direct electrical output that is capable of complete device-level integration. The steady reduction rate of a reversible redox species at an embedded microband working electrode is monitored amperometrically. Only one working electrode of arbitrary width is required; all three electrodes, including counter and reference electrodes, are integrated on-chip for complete miniaturization of the sensor. Experimental results are complemented by a theoretical framework including a full 3D electrochemical model as well as empirical mass transfer correlations and scaling laws. When the sensor is operated in the convective/diffusive transport controlled mode, the output signal becomes a predictable function of velocity in two distinct regimes: (i) in the low velocity regime, the signal is directly proportional to flow rate, and (ii) in the high velocity regime, the signal scales as the cube root of the mean velocity. The proposed velocimetry technique is applicable to all practicable pressure-driven laminar flows in microchannels with known cross-sectional geometry.
KeywordsMicrofluidics Velocimetry Flow sensor Redox electrochemistry
The funding for this research provided by a Natural Sciences and Engineering Research Council of Canada (NSERC) strategic grant is highly appreciated.
- Bard AJ, Parsons R, Jordan J (eds) (1985) Standard potentials in aqueous solution. Marcel Dekker, New YorkGoogle Scholar
- Fu R, Li D (2006) Flow velocity measurement in microchannels using temperature-dependent fluorescent dye. Microfluid Nanofluid (in press). DOI:10.1007/s10404–006–0102-yGoogle Scholar
- Incropera FP, De Witt DP (1990) Fundamentals of heat and mass transfer, 3rd edn. Wiley, New YorkGoogle Scholar
- Kakac S, Shah RK, Aung W (1987) Handbook of single-phase convective heat transfer. Wiley, New YorkGoogle Scholar
- Newman J, Thomas-Alyea KE (2004) Electrochemical systems, 3rd Edn. Wiley, HobokenGoogle Scholar
- Nusselt W (1923) Der Warmeubergang in den Verbrennungskraftmaschinen. VDI Z 67:206–210Google Scholar
- Probstein RF (2003) Physicochemical hydrodynamics—an introduction, 2nd edn. Wiley, HobokenGoogle Scholar