A miniaturised industrial chemical sensing system

Project Information

Grant agreement ID: BRPR980787

Project closed

Start date 1 September 1998

End date 31 October 2001

Funded under

• Specific research and technological development programme in the field of industrial and materials technologies, 1994-1998

Total cost

No data

EU contribution

No data

Coordinated by

DANFOSS A/S
Denmark

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Deliverables

Development of separations methods based on electro-osmotic pumping

This work investigated the integration of field-amplification stacking (FAS) with capillary electrophoresis (CE) on-chip. Instead of pushing detector performance to the limit, FAS can pre-concentrate the sample analyte on-chip into a narrow zone prior to a CE separation, to improve the sensitivity of the device. FA is widely used in conventional capillary systems but although it is a fairly straightforward method, its transfer onto a microchip requires careful control of the injection process and separation conditions. Two sample pre-concentration methods are of interest for integration onto chip: field-amplification stacking (FAS) in low-conductivity sample buffers and isotachophoresis in discontinuous buffer systems. These techniques are known to show concentration efficiencies of 5 to 1000-fold and have been widely used for the separation of trace ions both on and off-chip. New aspects being considered in our work are the optimisation of channel geometries as well as injection and separation conditions for chip-based systems. The final goal of this research work is the development of a miniaturised analysis system with a wide dynamic measurement range. Since CE separations can provide information on more than one analyte at a time, this type of device could form the basis of a sensor with multianalyte capability.

Mixing and dispersion in micro-channels with different geometry have been studied theoretically and experimentally

Dispersion theory is a very important tool for design of sensor systems with short response time and of sensor systems based on pumps giving a pulsating flow. Also, this knowledge points to ways of making on-line dilution of concentrated samples in sensors. Dispersion is well described in pressure driven flow-systems using tubes (circular cross-section channels). Most microsystem-based flow systems, however, are based on channels of non-circular cross-section. If deep reactive ion etching (DRIE) is used to form the channels, as in this project, channels have a rectangular profile, and can be narrow and deep. Therefore an analysis of dispersion in rectangular micro channels has been presented, addressing the most significant dispersion effects related to non-circular flow channels and pointing to important optimisation criteria for future µ-TAS development. It is shown that most practical rectangular channel cross-sections result in considerably higher dispersion than mathematically well-described structures such as circular tubes and infinite aspect ratio rectangular channels. Both analytical modelling as well as numerical simulations have been considered. Extensive experimental dispersion data confirm the validity of the theory.