Miniature Electromagnetic Bio-Sensor for Biomolecules Analysis in Aqueous Solution

This communication presents a miniature bio-sensor able to analyze bio-molecules in aqueous solution without any labeling or bio-functionalisation. The physical principle relies on the interaction between microwave electromagnetic waves and bio-liquid. The resulting electrical signal provides specific information on the solute: its concentration and its type. Operation in the GigaHertz regime assures an optimal coupling between the electromagnetic waves and the aqueous solution (theoretically maximal around 20 GHz). The fluid is localized over the sensing area thanks to a microfluidic channel, which permits to reduce the consumed liquid down to the microliter scale. The electromagnetic sensor is realized with microtechnologies, which assure a
millimeter-size sensor.Results : The technique is based on performing the â-oedielectric spectroscopyâ- of bio-liquids, technique which consists in measuring over frequency (e.g. spectroscopy) the dielectric permittivity of the liquid under test. Such a parameter is one of the physical characteristics of matter and is in fact a complex number. Its real part corresponds to the square of the refractive index (which gauges the decrease of the light speed in the matter referred to the speed in vacuum) and its imaginary part, which gauges the energy absorbed by the matter.
Experimental results point out two major behaviors : 1) both parameters are to proportional to solute concentration, which gives a robust way to deduce from measurements the solute concentration in aqueous solution.2) the ratio between the two parameters are then concentration independent and we prove that this ratio is biomolecule-dependent.This last result represents a key feature of the electromagnetic sensing technique as we can envision to, without any labeling and any bio-functionalization, identify and monitor the variation of any biomolecule in any
biomaterials: in aqueous solution, in a living cell, in tissue or organs.

F. Artis, D. Dubuc, J-J. Fournié, M. Poupot, K. Grenier
LAAS CNRS-CRCT INSERM, Toulouse
fartis@laas.fr