The team :
Permanent staff :
- 4 Distinguished/Full Professors : Ch. Brosseau, P. Queffelec, B. Rouvellou, Ch. Tannous
- 6 Associate/Assistant Professors : A. Chevalier, S. Lasquellec, V. Laur, B. Lescop, J.-L. Mattei, S. Rioual
- 1 Research engineer : A. Maalouf
Non-permanent staff :
6-9 PhD students, 2-4 Post-Doc. students, fixed-term contractant
Our scientific activities focus on the following three axis :
- Production and implementation of functionnal materials for microwave devices manufacturing processes
Our investigations focus on the manufacturing and implementation of functional materials for the development processes of devices intended to be used in the microwave range.
Research themes and Applications areas :
- Miniaturization of electronic devices for mobile communications has led to increasing demand for the reduction of antenna dimension. In this field we realize low-losses magnetodielectric ceramics (based on soft ferrites) with controled porosity, that found applications from the low VHF band (30MHz) to the UHF band (1.2 GHz).
- In wireless applications, circulators are used for transmitting and recieving signals silmutaneously using a single antenna. We achieved the design of integrated circulators (3GHz-40GHz), with putting emphasis on the low cost aspect of the production. Within this context :
- We consider integration of the devices using LTCC technology
- We implement the Molded Interconnect Device technology to the realization of self-biased circulators.
- We study and synthesize nanosized Baryum ferrites and Strontium ferrites platelets , that are further oriented such as to realize a magnet with high remnant magnetization value.
- Innovative materials obtained from 3D printing :
- Study and development of loaded polymers for 3D printing, that show either low dielectric losses, either absorption properties, for applications in the microwave range.
- A Simple and Low-Cost Solution was developped to get full 3-D printed microwave termination.
- Developpement of a generalized permeability tensor model able to describe the permeability tensor of a ferrite sample whatever its magnetization state. This model is coupled to a homemade 3D multi-scale magnetostatic analysis program, which describes the evolution of the magnetization through the definition of a hysteresis loop in every mesh cell. These computed spectra are integrated into 3D electromagnetic simulation software that retains the spatial variations of the ferrite properties by using freshly developed macro programming functions. This new approach allows the designers to accurately model complex ferrite devices.
- We develop new theoretical and experimental tools enabling the broad-band RF characterization of anisotropic ferrites. The study focus on characterization of microwave losses thanks to a unique parameter: the damping factor. While microwave properties of ferrite are usually described with two different resonance linewidth parameters, DH and DHeff extracted from the curve of imaginary part of permeability with the static applied field at a given frequency. This unique dynamic property combined with the static characteristics (saturation magnetization, anisotropy field) would be the input parameters of generalized permeability tensor model which then would be able to predict the microwave behavior of the ferrite whatever its magnetization state is.
- Electromagnetism of heterogeneous materials and biological structures
Our current research activities on these topics mainly focus on numerical and experimental studies of the interactions between electromagnetic waves and nanosized structures that can give rise to interesting phenomena, e.g. plasmon resonances of complex structures. First, we want to develop heterostructures that combine multiple functions or properties that are not obtainable in individual components such as the magnetoelectric effect. Our work is based on the development of nanofabrication techniques, together with modern nanocharacterization techniques such as microwave and near-field optical imaging and the emergence of quantitative electromagnetic simulation tools (finite-element, FDTD, Monte Carlo, molecular dynamics).Second, one of the ultimate challenges in biology is to understand the relationship between the structure, function, and dynamics of biomolecules in their natural environment, i.e. the living cell. Although modern molecular biology has made enormous progress in identifying different cell components, both inside and at the cell membrane, observing molecular processes in living cells is still a major issue. Electrostatic forces between cells in tissue are thought to be of crucial importance for tissue engineering based on energetic, time scale, and cell numbers consideration. The aim of this multidisciplinary project is to study the details of correlations between electromagnetic excitation and mechanical response of biological materials (cells and tissues). The good agreement between multiphysics simulation data and preliminary experimental results provides a convincing example of in silico multiscale models of tissues. By tuning the field frequency it is possible to adjust the Maxwell electric stress of a group of biological cells and hence the cell-cell interactions. Additionally, we develop a multiscale approach, based on both experimental and computational methods, to investigate the collective dielectric response of cell assemblies. We envision that such behavior might be of utmost importance for tissue engineering and electroporation mechanisms.
- Environmental sensors
Our research activities focus on the development of RF sensors for several applications such as environmental parameters monitoring, structural health monitoring, medical applications,…. The proposed sensors are based on the interaction between propagating electromagnetic waves and specific functional materials or media. A variation of this interaction due to a change of properties of materials ensures the sensitivity of the method. For that purpose, we provide a wide variety of material characterization and elaboration techniques including XPS, XRD, microscopies, RF and DC characterization, magnetic characterization, PVD, sol-gel,…After their characterization, depending on chosen sensor architecture, materials are integrated in dedicated RF components such as transmission lines or resonators. In the last few years, we focused in particular on the development of chipless sensors inspired from the chipless RFID technology. The advantage of such wireless sensors concerns the absence of any battery or electronic component making them suitable for applications in harsh environments (temperature, pressure, dust,…). Within this context, sensors sensitive to corrosion of metals and diffusion of water in porous dielectric media were produced for structural health monitoring. Other applications are currently explored through the development of new functional materials and methods.