Flow-rate measurement via conductivity monitoring in microfluidic devices

Paul V. Rainey; S. J. Neil Mitchell; Harold S. Gamble

doi:10.1117/12.395659

18 August 2000 Flow-rate measurement via conductivity monitoring in microfluidic devices

Paul V. Rainey, S. J. Neil Mitchell, Harold S. Gamble

Proceedings Volume 4177, Microfluidic Devices and Systems III; (2000) https://doi.org/10.1117/12.395659
Event: Micromachining and Microfabrication, 2000, Santa Clara, CA, United States

Abstract

This paper investigates methods of flow rate quantification in micro- fluidic devices, using electrodes to measure the conductivity of solution. Conductivity changes occur when liquid flow causes movement of the boundary between two solutions of differing conductivity. The fabrication technology for the micromachined silicon structures is based on anisotropic etching and anodic bonding to glass. The silicon processing is simplified by using a single-mask process, whereby 9 - 15 mm long, 50 - 100 micrometers wide capillaries and access through-holes are created with a single etch step. Thin film gold electrodes patterned on the glass provide contact with the liquid in the capillary. The current monitoring method, used in capillary electrophoresis, is employed to determine conductance-time waveforms during electroosmotic pumping. The waveforms for silicon based devices are distorted due to oxide capacitance and the profiles of the ends of the channel. The transitions are much more linear for reference devices formed using standard glass capillary tubing. Electrical models are developed for the devices and these are used to determine flow velocities and hence volume flow rates of liquid.

Citation Download Citation

Paul V. Rainey, S. J. Neil Mitchell, and Harold S. Gamble "Flow-rate measurement via conductivity monitoring in microfluidic devices", Proc. SPIE 4177, Microfluidic Devices and Systems III, (18 August 2000); https://doi.org/10.1117/12.395659

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