Microfluidic Mixing Device With Integrated Dual-Band Microwave Sensor

A microfluidic mixer is integrated with a dual-band microwave resonator to allow in situ monitoring of mixing two liquids. The resonator is a complementary double split-ring resonator, which is etched in the ground plane of a microstrip transmission line. The output channel of the mixer is conducted below the ground plane in the near field of the resonator. Electromagnetic and fluid dynamic simulations have been performed to design optimal channel configurations for this section to increase the sensitivity, minimize the volume of the required liquid sample, and eliminate unwanted microfluidic mixing. The frequency variation of the first two resonances is monitored by measuring the transmission parameter of the microstrip line. The performance of the device is demonstrated by mixing saline solutions of different concentrations and the transmission spectra of different chemicals are also presented. It is shown that the device can allow unambiguous chemical identification by simultaneous monitoring of the two resonances. The total amount of fluid required to operate the device is less than 8 mu L.