Circuits intégrés optiques et diélectrophorèse: vers des applications pour la mesure de concentration bactérienne

Master thesis
Master Recherche / PFE
(5 to 6 month)
Integrated optical circuits and dielectrophoresis: Towards bacterial sensing applications

IMEP-LaHC is one of the leading laboratories in the field of integrated optics, and more specifically of photonics on glass. Striving for innovation, one of our goals is to fabricate integrated devices dedicated to sensing applications such as bacteria detection. Indeed, monitoring of bacterial concentration is critical in various fields such as agri-food industry or environmental monitoring.
For this aim, IMEP-LaHC develops collaborations with the Institut des Géosciences et de l’Environnement (IGE) and the Laboratoire des Microbiologies Signaux et Microenvironnement (LMSM). For these partners, the design and fabrication of a compact, reusable and portable optical sensor would be a major step for efficient and continuous in-situ measurements. Our objective is to develop an innovative solution that does not require a functionalization layer to trap the bacteria in the sensing area. We thus aim at co-integrating optical waveguides with electrodes designed for dielectrophoresis (DEP) applications1,2.
An alternative voltage is applied on metallic electrodes in order to create a non-uniform electric field. It can trap polarizable particles such as bacteria close to an optical waveguide, leading to a change of the refractive index of its superstrate.

This Master’s thesis is the continuation of a previous Master’s subject that has delt with the DEP electrode’s design and fabrication. This one is focused on the co-integration of the electrodes with a Mach-Zehnder optical interferometer and a microfluidic cavity. The aim is to provide a proof of concept of a first sensor’s design by detecting bacteria-sized latex beads as a model.

The main specifications of the subject are:

• The realization and characterization of a device co-integrating the DEP electrodes with an optical straight waveguide.
• The design and fabrication of a sensor’s prototype co-integrating the DEP electrodes with a Mach-Zehnder interferometer
• A first validation of the prototype via the sensing of bacteria-sized latex beads.

To fulfill these objectives, the student will become familiar with the subject through a bibliographic research on integrated sensors dedicated to bacterial concentration and Mach-Zehnder interferometer. He/she will also be trained for various techniques of design and fabrication.
The training includes in particular:

•  Clean room processes for the metallic deposition and integrated optics
•  microfabrication processes for the realization of the microfluidic chamber
•  integrated optics on glass technology (ion diffusion on glass)
•  simulation tools dedicated to guided optics propagation
• optical characterizations of integrated devices

This Master’s subject is a preliminary work for a future PhD subject, dealing with the integration of a full bacteria sensor3. Depending on the student’s motivation and progress, a last task could deal with the integration of the optical function in a more complex circuit or the optimization of the microfluidic chamber (fabrication process, material used…)

Advisors:
Elise GHIBAUDO elise.ghibaudo@grenoble-inp.fr – 04 56 52 95 31
Davide BUCCI davide.bucci@phelma.grenoble-inp.fr 04 56 52 95 39
laboratoire IMEP – LaHC
MINATEC – INPG, 3 Parvis Louis Néel BP 257 38016 Grenoble Cedex 1 – France

1 L. Cui, T. Zhang and H. Morgan, J. Micromech. Microeng. 12 (2002) 7–12
2 J. Suehiro et al, J. Phys. D: Appl. Phys. 32 (1999) 2814
3 S. Tokonami, T. Iida, Analytica Chimica Acta 988 (2017) 1-16

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