This paper reports the design, simulation and experimental validation of an accurate liquid sensing technique in the nano-liter range. It is suitable for the detection and quantification of very small contents of liquid samples containing biological cells. The biosensor is based on an open-ended interdigitated capacitor (IDC) within a microfluidic channel. The microwave structure including the IDC is patterned in coplanar waveguide technology. The microfluidic channel is 100 µm thick and the IDC covers an area of 150 µm width and 90 µm length. This leads to a volume under analysis much lower than a nano-liter which allows the noninvasive and contactless microwave investigation of biological cells in their culture medium.This micro-device is used to extract the complex permittivity of liquid media from the measured scattering parameters within the frequency band ranging from 0.2 to 25 GHz. For ease of use, a SMAconnectorized version of the device with spring contacts probes to the biosensor is also proposed. Results concerning microparticle detection within the media are also presented, extending the use of the sensors to cellular environments.

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This article reports an open-ended coplanar waveguide line (OE-CPW) allowing the characterization of a liquid medium by dielectric spectroscopy within the 0.4-6 GHz frequency range. This proposed technology allows characterization of a medium placed in an integrated microfluidic channel located at the end of the CPW line. The medium under test occupies a volume of analysis of less than one nanoliter, scale allowing measurements of one to a few biological cells. RÉSUMÉ : Cet article pré sente une ligne coplanaire (CPW) à extré mité ouverte permettant la caractérisation d'un milieu liquide par spectroscopie diélectrique dans la bande de fré quences 0,4-6 GHz. Le capteur proposé permet de caractériser un liquide s'écoulant dans un canal microfluidique intégré au dispositif et positionné à l'extrémité de la ligne CPW (ligne à effet de bout). Le milieu sous test occupe un volume d'analyse de l'ordre du nanolitre, é chelle permettant d'effectuer une mesure sur une ou plusieurs cellules biologiques.