Appel à candidature pour une thèse

𝐏𝐫𝐨𝐣𝐞𝐜𝐭 𝐃𝐞𝐬𝐜𝐫𝐢𝐩𝐭𝐢𝐨𝐧:

Even though safety guidelines prescribe EM exposure limits for people in restricted environments and for the general public in unrestricted environments, there is always public concern regarding safety issues for new/emerging wireless systems. One reason is the fact that, for example, the world health organization (WHO) recommends assessing exposures from new wireless network technologies, but right after its publication, several emerging wireless systems such as the 5G wireless communication system appeared.

Shielding the human body in an appropriate way from RF radiation is hence of great demand in order not to limit the applications of electronic products. Besides, that RF power in addition to the large amount of ubiquitous EM energy in atmosphere (e.g., TV/radio broadcasting, WLAN, and mobile phone signals) can be harvested to energize low-power electronic devices. Since the amount of harvested ambient energy is usually limited, depending on the targeted application, a hybrid harvesting system combining multiple sources has to be considered. In case of a body-worn harvester, in addition to the RF energy harvesting, body heat and movements can be complementary sources of energy.

This potentially lowers the cost of a system by eliminating the need for batteries and/or power supply resources. More importantly, considering the main focus of national and international on improved energy efficiency and reduced carbon emissions, such a device can easily find application in ambitious projects such as intelligent buildings and smart cities enabled by technologies such as cellular or Wi-Fi wireless sensor networks.

This project aims to simultaneously mitigate incoming EM waves towards the human body while collecting RF, body heat and kinetic energy simultaneously to energize low-power electronic devices.

Electromagnetic metasurfaces can be potential candidates for wearable applications due to the following:

• metasurfaces have the desirable traits of not only blocking/reflecting/mitigating unwanted polarization-independent EM waves, but also being much thinner than the wavelengths of interest. More importantly, they can be tunable, switchable, reconfigurable and programmable by custom integrated circuit technology. In addition, they can be designed on either flexible or transparent materials
• metasurfaces have the potential to harvest the available propagated waves and convert them into usable guided waves instead of dissipating them in the medium. For example, similarly to metasurface absorbers, in a metasurface harvesters, the small resonators, at their resonance frequency, effectively couple to the incident EM wave and capture the EM power from the ambient. In the absorbing functionality, the captured EM power dissipates within the structure as either ohmic or dielectric loss, whereas in harvesting application, the captured power by each resonator is channeled to a rectifying circuit through a network which combines the power captured by one or multiple resonators.

Host institution: ESEO (France)

Enrolment in PhD program: INSA RENNES (France)