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Micro- and meso-scale electrostatic energy harvesting systems have high efficiency at the higher-frequency part of the spectrum due to the natural frequencies of micro-structures lying over a range from hundreds of hertz to megahertz. However, many real-life applications related, in particular, to wearable systems, structural monitoring, or the Internet of Things, are characterized by low-frequency environmental forces. The main goal of this letter is to demonstrate that the placement of a stopper that limits the motion of the proof mass and causes soft impacts in an electrostatic kinetic energy harvester is responsible for an effect known as frequency up-conversion. This means that there is a significant response to “non-resonant” frequencies away from the natural frequency of the structure leading to effective energy conversion to the electrical domain. The concept summarizing this effect is presented and modeled, and an experiment carried out on a microscopic electrostatic harvester is presented to prove the concept.

We report the first experimental proof of concept of a new electromechanical adiabatic logic family operating without any kind of electrical and mechanical contacts. Based on comb-drive actuators and standard microelectromechanical system (MEMS) microfabrication, we demonstrate the cascadability of logic gates up to 170 °C, and operation in the kilohertz-range under a power supply of 4.5 V. Assuming that state-of-the-art microfabrication can downscale our MEMS gates by a factor of 100, we expect a dissipation of 0.1 aJ/op (24 $\text{k}_{\text {B}}\text{T}$ ) at 250 kHz at 45 mV. This study paves the way toward new reliable low-power electromechanical digital circuits.

Summary Dew water, mostly ignored until now, can provide clean freshwater resources, just by extracting the atmospheric vapor available in surrounding air. Inspired by silicon-based solar panels, the vapor can be harvested by a concept of water condensing panels. Efficient water harvesting requires not only a considerable yield but also a timely water removal from the surface since the very beginning of condensation to avoid the huge evaporation losses. This translates into strict surface properties, which are difficult to simultaneously realize. Herein, we study various functionalized silicon surfaces, including the so-called Black Silicon, which supports two droplet motion modes—out-of-plane jumping and in-plane sweeping, due to its unique surface morphology, synergistically leading to a pioneering combination of above two required characteristics. According to silicon material's scalability, the proposed silicon-based water panels would benefit from existing infrastructures toward dual functions of energy harvesting in daytime and water harvesting in nighttime., Graphical abstract, Highlights • Unusual condensation dynamics occur on the hierarchical Black Silicon metasurface • Near-zero water removal time and good water yield are simultaneously achieved • Great scalability and multifunctionality are accessible to the proposed water panel, Materials design; Materials property; Metamaterials; Surface

As for any electrostatic transducer, triboelectric energy generators (TENGs) need to maximize their bias voltage for a good kinetic-to-electrical energy conversion. If several hundreds of volts can be obtained directly by triboelectric contacts for some state-of-art devices, unstable charge-pump (UCP) conditioning circuits can also be used to reach such high values with more basic TENGs. Whatever the chosen solution, this high-voltage must be reduced to a few volts to power an electronic device. In this abstract, we first compare the three main UCPs and we propose to use an autonomous MEMS micro-plasma switch in a Buck DC-DC converter in order to maximized the voltage across the TENG while obtaining a low voltage rectified output without any external control.

In this paper, we explore the far-field radiative thermal rectification potential of common materials such as metals,ceramics and doped semi-conductors using radiative and thermo-radiative properties extracted from literature. Seventeen different materials are considered. The rectification coefficient is then calculated for 136 pairs of materials; each pair can be used for the two terminals of a radiative thermal diode. A thermal bias of 200 K is considered. The choice of materials and thermal bias value are only bound by data availability in literature. Obtained results, highlight new candidate materials for far-field radiative thermal rectification. They also highlight materials where thermal rectification is not negligible and should be considered with care in heat transfer calculations when considering systems subject to a comparable thermal bias and where these materials are used. Among the materials studied, undoped Indium Arsenide (InAs) shows great promise to be employed for thermal rectification, with a thermal rectification ratio reaching 96.35% in combination with other materials. Obtained results pave the way for an optimized design of thermal radiation control and management devices such as thermal diodes.

Scavenging the energy of human motions has attracted widespread attentions with the development of wearable electronics. This paper for the first time proposed a progressive triboelectric nanogenerator based on macro-triangle-prism-shaped conductive polyurethane (PU) foam and polytetrafluoroethylene (PTFE) film, which occupy the top and bottom spots of the triboelectric table respectively. The proposed macro-structured conductive PU foam also integrates the functions of spring, spacer and electrode. Thanks to the innovative structures and chosen of the materials, an extended current pulse width is obtained. A maximum RMS power density of 100 nJ/cm2/tap was obtained with a 60 MΩ resistive load and press force of 10 N@5 Hz. By regulating the TENG with a Bennet doubler conditioning circuit, the ubiquitous voltage saturation phenomenon when charging a storage capacitor using full-wave rectifiers is avoided. Moreover, the energy per cycle, charging efficiency and totally stored energy can be exponentially pumped up. With a Bennet circuit charging a 5 nF capacitor, a harvested energy density of ~ 710 nJ/cm2/tap was obtained when voltage across the capacitor was 400 V. Putting the device under sole within 25 human steps, the totally stored energy was 0.43 mJ with a Bennet circuit, 3.6 times higher than that using a full-wave rectifier (0.12 mJ). The Bennet was proven better for regulating the triboelectric nanogenerators with long operation-time compared to the classical full-wave rectifier.

Recently, electrostatic kinetic energy harvesters regained strong attention through the development of new triboelectric generators for harvesting green and renewable energy. These devices use a triboelectric dielectric layer as electret for polarizing their capacitance and they behave similarly to electret generators. However, triboelectric-based electret nanogenerators (T-ENG) have specificities arising from the contact electrification phenomenon and leading to different performances. For better understanding T-ENG, we investigated their electrical modeling with lumped-elements and multiphysics simulation in light of last researches on electret generators. To take into account T-ENG specificities, we experimentally measured the amplitude of the triboelectric effect on perfluoroalkoxy alkane films. This approach allowed fully simulating T-ENG and the model was found in agreement with experimental results. Understanding and verifying the model is capital, but to go further toward the application of T-ENG, we reused two electret circuits to extract the T-ENG model parameters in view of facilitating their realistic modeling and practical development into application.

International audience; Enhancing residential buildings energy efficiency has become a critical goal to take up current challenges of human comfort, urbanization growth and the consequent energy consumption increase. In a context of integrated smart infrastructures, sensor networks offer a relevant solution to support building energy consumption monitoring, operation and prediction. The amount of accessible data with such networks also opens new prospects to better consider key parameters such as human behaviour and to lead to more efficient energy retrofit of existing buildings. However, sensor networks planning and implementation in general, and in existing buildings in particular, is a particularly complex task facing many challenges and affecting the performances of such a promising solution. In the present paper, we report on a field experiment of a sensor network deployment involving more than 250 sensors in three collective residential buildings in Paris region for the evaluation of a deep energy retrofit. More specifically, we describe the whole process of the sensor network design and roll-out and highlight the main critical aspects in such complex process. We also provide a feedback after several months of the sensor network operation and preliminary analysis of collected data. Reported results path the way for an efficient and optimized design and deployment of sensor networks for energy and indoor environment quality monitoring in existing buildings.