Electrical stimulation combined to molecular approach is a promising way for the reformation of damaged neural circuit in the central nervous system after a lesion or a neurodegenerative disease. Placing neural stimulators all along the reforming circuit is certainly key for the complete re-innervation. However, the current tethered neural stimulation technologies do not allow to position the implants over several centimetres in a custom way because of their large spatial clutter. Thus new implantable neurostimulation technologies must be developed to meet this need. In order to fill this gap, the present project suggest to create wireless and battery-free stimulators powered by ultrasound. In order to reach dimensions below 200µm required for intracerebral implants, the consortium will fabricate and use piezoelectric micromachined ultrasonic transducers coupled to stimulating microelectrodes. This new concept of wireless and battery-free electric neural stimulator will be tested in vitro on retinal explants, a gold standard to study axonal regeneration.

Small-scale kinetic energy harvesting is a candidate technique for the self-powering of autonomous systems of small sizes, by converting part of their ambient mechanical energy into usable electrical energy. Among different types of kinetic energy harvesters, triboelectric kinetic energy harvesters (t-KEH) are relatively easy to fabricate and are compatible with irregular or low-frequency mechanical inputs. They also have a relatively small environmental footprint compared to other technologies. The size these devices is on the order of the centimeter cubed, and the targeted power levels range from the microwatt, to the milliwatt for the bigger devices. So far, research efforts on t-KEHs have been focused on optimizing the materials and geometries of triboelectric transducers. Electrical interfaces are key component of t-KEH but have been the subject of relatively few systematic research efforts. As a result, practical limits on the energy deliverable by these devices remain unclear. Besides, a systematic procedure for the optimal design of t-KEHs electrical interfaces is lacking. But as the design of the transducer itself, the choice of the electrical interface is a determining factor of the performances of t-KEHs. These performances also depend on the nature of the mechanical inputs in the application context. Specifically, the design of the t-KEHs electrical interfaces should account for irregular actuation of the triboelectric transducer. Such irregular or random inputs are present in much of the applications targeted by t-KEH (e.g., human body movement). In this project, we will build a systematic flow for the design of optimized t-KEH targeting applications with irregular mechanical excitations. Our methodology will result in an optimal choice of the electrical interfaces. These interfaces will be based on a specific class of conditioning electronics for electrostatic transducers, called charge-pump conditioning circuits. We will first build a theory of such circuits. We then plan to leverage this theory to optimize the energy conversion by the t-KEH. Notably, the electrical interfaces we propose feature a control of the state of the conditioning circuit, so as to implement a maximum power point tracking functionality. This control is based on a statistical model of the input excitations for the targeted application context, on the properties of the used triboelectric transducer, and on the useful load’s energy consumption requirements. Our systematic design method will be illustrated by the fabrication of a complete prototype of t-KEH operating in realistic conditions. As a byproduct, the project will also clarify the physical limits on energy conversion for any given application context, accounting for the electrical interface, the statistical properties of the external mechanical inputs, and the physics of the triboelectric transducer.

We propose a near zero-power digital circuit topology by combining gradual transitions and electrostatic interactions between logic states by introducing new device type. As transistors are not adequate candidates for this new logic paradigm, we introduce an electrostatic-controlled MEMS devices in a dielectric liquid to obtain leakage-free, high-dynamic, high-density and energy-reversible variable capacitors. These devices must be combined to form the basement of a future energy-aware processor by introducing a flexible trade-off between computation speed and energy dissipation. Further fundamental advances are awaited such as a better knowledge of the dielectric liquid at micro-scale or the fringe-field effect in micro-scale electrostatic actuators.

Silicon carbide (SiC) is proposed as material to develop single material BMIs addressing the issue of their low lifetime. SiC is a biocompatible semiconductor, stiff material and therefore highly flexible for small thickness (<15 µm)). Moreover, small electrode thickness results in minimal foreign body response. The three SiC crystal phases (amorphous, poly- and single-crystalline) will be investigated as active electrode, insulating and support material. The proof-of-concept will be performed with the elaboration and in-vivo evaluation of an all-SiC very thin (<15µm) µECoG exhibiting long-term stability (several months), low impedance (<30kO at 1kHz), noise level (<3µV RMS for 1-5000Hz) and signal quality (surface multiunit/unit activity/LFPs detection). A nanowire array formation in electrode area will be employed to increase the recorded signal. Amorphous SiC surface will be functionalized for minimum tissue inflammation purposes.

The purpose of the DICOREV project is to pave the way for a new technique to characterize electromagnetic antennas and scattering objects in reverberation chambers. Recent advances in wireless communications, radar imaging, monitoring or multi-parameter sensing have made the characterization of systems equipped with radio-frequency antennas highly challenging. For instance, arrays of ultra-wideband antennas of MIMO (multiple input-multiple output) and massive MIMO systems are becoming increasingly large, especially for millimeter-wave 5G communication systems. Miniaturized and embedded antennas distributed in any piece of equipment are also involved in the context of the internet of things where they are associated to sensors transmitting various types of data. Those systems therefore require developing new characterization techniques to measure the associated communication rate, control their in situ performance and maintain their efficiency. The need of Radar Cross-Section (RCS) measurement has also strongly increased in recent years due to the development of radars for civil applications, for transportation systems. Here, we exploit the cross-correlation of the diffuse field generated by sources in a chaotic reverberation chamber to passively retrieve the impulse response between receiving antennas both in the centimeter- and millimeter-wave ranges. Mode-stirred reverberation chambers (RC) are now used as an alternative solution to anechoic rooms to measure antenna performance such as the efficiency, the sensitivity or the diversity gain for multiple antennas. Instead of mimicking free-space propagation, the field generated within an RC is naturally diffuse so that receiving antennas are illuminated by random plane waves. The consortium that gathers leading experts in the fields of noise correlation, wave chaos and reverberation chambers will progressively acquire theoretical and experimental knowledge of the specific properties of electromagnetic cross-correlation in RCs. Even though it has led to spectacular results in seismology, the ambient noise Green’s function retrieval method still remains largely unexplored in electromagnetism. We will provide a theoretical framework that can be exploited for a quantitative analysis of the cross-correlation function. This will be achieved by taking advantage of the universality of the field statistics within a chaotic cavity. The statistical properties of the RC and the distribution of noise sources ensuring the convergence of the cross-correlation toward the impulse response will be extracted and verified numerically and experimentally. The extraction of the coupling between two antennas will be investigated and demonstrated using different kinds of noise sources ranging from ambient thermal radiations to perfectly controlled sources. The performance of the proposed technique will be compared to usual active measurements in an anechoic room for well-known antennas as a proof-of-concept. The cross-correlation technique will overcome current limitations of coupling measurements between two receiving antennas which do not have the possibility to be turned into their emitting modes. It will then be extended to multiple input-multiple output systems and will provide a great simplification of the setup to measure the mutual coupling matrix of an antenna array which controls the performance of MIMO communication and radar imaging systems. Finally, it will be used to extract the radiation pattern of miniaturized and integrated antennas by recording the cross-correlation function on a set of sensors in the vicinity of the device under-test. This contactless approach is crucial because cables strongly disturb the radiation patterns of those antennas. Retrieving scattering pattern of objects for RCS measurements will also be explored especially in the case of extended objects-under-test.