Microfluidic biosensors for microwave dielectric spectroscopy

This paper deals with the development and characterization of label-free microfluidic biosensors ded-icated to the microwave dielectric spectroscopy of small volumes and flowing micro-scale particles.Especially, microwave dielectric spectroscopy offers unique capabilities to investigate intracellular prop-erties of biological cells, which are informative on many biological processes. This paper presents twoprototypes of high frequency biosensors able to operate in the microwave frequency range. Both arebased on capacitive detection either in a broadband or resonant mode. Thick gold metal electrodes havebeen investigated to perform high sensitive analysis, while a microfluidic system was implemented overthe RF circuit so that flowing liquid minimally impacts global losses of the system and has hence a limitedeffect on sensor sensitivity. Particles to be tested are manipulated to be accurately located in the detectionarea using dielectrophoresis techniques. To demonstrate the proposed approach and assess the detec-tion capabilities of such sensors, HF measurements (up to 8 GHz) have been performed on calibratedsize polystyrene beads (12 m diameter) and compared with full-wave electromagnetic simulations.Measured capacitance contrasts are typically around 1 fF at 5 GHz. Preliminary experimentations werethen achieved on cancerous cells. The presented results demonstrate the high potential of the proposedapproach to develop new label-free analysis tools with a large application range, either in the diagnosisor treatment fields.