Contactless conductivity detection in LTCC technology for microfluidic devices

In this paper we report on a microfluidic device for contactless liquid conductivity detection realized in Low Temperature Co-fired Ceramics (LTCC). An opposite-electrode arrangement serving as the detector is situated on the outside of the device, avoiding direct contact with the fluid. The excitation signal gets coupled into the microfluidic channel through the LTCC wall. Ceramic tapes with higher permittivities as compared to standard materials have been used for device fabrication, significantly improving the coupling of the measurement signal. The response of the detector was modeled to obtain the frequency range where the device is most sensitive to changes in liquid conductivity. Measurements with varying concentrations of an NaCl solution have been carried out to show the feasibility of the device for CE-separations.