Description
Date depot: 19 novembre 2018
Titre: Development of wireless energy harvesters based on magnetoelectric transducers for biomedical applications
Directeur de thèse:
Gérard SOU (GeePs (EDITE))
Encadrant :
Alexis BRENES (LISITE)
Domaine scientifique: Sciences et technologies de l'information et de la communication
Thématique CNRS : Non defini
Resumé:
E-Health and the Internet of Things (IoT) are two
growing markets, related to each other by the interconnection of nomadic objects
for the “quantified self”, where each patient can perform his own physiological
tests. For that purpose, one of the technological challenges lies in the power autonomy,
since energy must be supplied to the system with a minimum interaction from the
outside (the device can for instance be directly implanted inside the body of
the patient and thus unreachable). Hence, the development of a wireless energy
harvesters has a very wide range of applications. In this context, magnetoelectric
(ME) materials arouse a significant scientific interest as energy transducers
to transform electromagnetic energy provided from the outside into electrical
energy available to power the system.
ME materials are laminar composites based on
piezoelectric and magnetostrictive layers (PZT/Terfenol-D type) glued together
with epoxy. The device is usually connected to an electrical interface via
deposited electrodes. When the ME material is driven by an external magnetic
field, magnetostrictive elements are subject to mechanical constraints and
motion. This motion is then transferred to the piezoelectric element which generates
a voltage between its electrodes. The conversion efficiency between the
magnetic excitation and the produced voltage is expressed by a magnetoelectric
coefficient in V/Oe [5,6]. The models and measures show that, at the centimeter
scale, the transmitted power at the resonance frequency is generally sufficient
(few mW) to power a functional sensor and its electronic interface circuit.
Then, the energy must be shaped (conditioned) and managed at the system level
(power management).
For piezoelectric energy
harvesters, many optimization strategies already exist to maximize the power
flow from the transducer to the energy storage unit [1,2,3,4]. This
optimization takes into account the impact of the energy harvesting circuit on
the overall performances of the system. Yet, to this day, no optimal solution has
been identified to fit the specific constraints imposed by magnetoelectric
resonators. Taking into account the specificity of magnetoelectric resonators at
the system level will be a key point of this thesis. The thesis will thus aim
at studying and designing the architecture of energy harvesting and conditioning
systems for magnetoelectric transducers.
Doctorant.e: Koteiche Ali