Novel impedimetric and perforated thermal flow sensor for inline chemical process analysis in micro residence time reactors

A novel impedimetric and thermal flow sensor chip with perforated membrane for the inline chemical process analysis in micro residence time reactors were developed. Sensors were optimized for reactors made of stainless steel with a hydraulic diameter in the range of ~1 mm. The impedimetric sensor chip consists of capacitively coupled interdigital electrodes made of MoSi₂ on a silicon substrate. The thermal flow sensor consists of a heater in between two thermocouples on a thin membrane containing small holes for pressure compensation. CFD simulations were conducted to study the influence of medium flow in the cavity below the membrane. A micro fluidic flow cell with sensor electronics was developed for the characterization of both sensors. Experimental results revealed that changes of less than 1% in the thermal and electrical properties of the liquid can be detected. Insofar, the combination of the impedimetric and thermal flow sensor chip enables the analysis of reactive mixtures in overpressure regime by means of 4 independent physical parameters.