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The rapid growth of wireless electronic devices has raised concerns about the harmful effects of leaked electromagnetic radiation (EMR) on human health. Even though numerous studies have been carried out to explore the biological effects of EMR, no clear conclusions have been drawn about the effect of radio frequency (RF) EMR on oligodendrocytes. To this end, we exposed oligodendroglia and three other types of brain cells to 2.4 GHz EMR for 6 or 48 h at an average input power of 1 W in either a continuous wave (CW-RF) or a pulse-modulated wave (PW-RF, 50 Hz pulse frequency, 1/3 duty cycle) pattern. RNA sequencing, RT-qPCR, and Western blot were used to examine the expression of C/EBPβ and its related genes. Multiple reaction monitoring (MRM) was used to examine the levels of expression of C/EBPβ-interacting proteins. Our results showed that PW-RF EMR significantly increased the mRNA level of C/EBPβ in oligodendroglia but not in other types of cells. In addition, the expression of three isoforms and several interacting proteins and targeted genes of C/EBPβ were markedly changed after 6-h PW-RF but not CW-RF. Our results indicated that RF EMR regulated the expression and functions of C/EBPβ in a waveform- and cell-type-dependent manner.

Significance The steady increase of electromagnetic radiation (EMR) in the environment, particularly the wireless signal, causes serious public concern over its potential negative impact on health. However, it is challenging to examine such impact on human subjects due to associated complex issues. In this study, we establish an experimental system for the investigation of EMR impact on mice. Using this system, we uncovered a causal relationship between 2.4-GHz EMR modulated by 100-Hz square pulses and increased wakefulness in mice. This result identifies sleep alteration as a potential consequence of exposure to excessive wireless signals., Electromagnetic radiation (EMR) in the environment has increased sharply in recent decades. The effect of environmental EMR on living organisms remains poorly characterized. Here, we report the impact of wireless-range EMR on the sleep architecture of mouse. Prolonged exposure to 2.4-GHz EMR modulated by 100-Hz square pulses at a nonthermal output level results in markedly increased time of wakefulness in mice. These mice display corresponding decreased time of nonrapid eye movement (NREM) and rapid eye movement (REM). In contrast, prolonged exposure to unmodulated 2.4-GHz EMR at the same time-averaged output level has little impact on mouse sleep. These observations identify alteration of sleep architecture in mice as a specific physiological response to prolonged wireless-range EMR exposure.

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.

Triboelectric-electret nanogenerators (T-ENG) are characterized by their high output voltage and small current and therefore a relatively low output power, making them limited to small power consuming electronics. Here we report a self-enhancing conditioning circuit (CC) that exponentially amplifies the output electrical energy converted from the mechanical domain of a T-ENG, in orders of magnitude compared to traditional CC. The circuit, working on the principles of Bennet’s doubler device, is inductorless and uses only diodes as automatic switches to reconfigure the charge storing capacitors between series and parallel modes. We previously reported this circuit in saturation and stable mode for T-ENG and compared the performances with half-wave rectifier. Here we investigate the circuit performance in exponential and unstable mode in comparison with half-wave and full-wave rectifiers. Theoretical analysis is presented to study the operation of the circuit and to find out the required conditions for the Bennet’s doubler to work in exponential boosting mode. Output performance of half and full wave rectifiers are compared theoretically. Simulations and experiments are performed to verify the theoretical discussions and to present the effect of non-ideal circuit elements on the output performance of the T-ENG.

A MEMS electrostatic kinetic energy harvester (e-KEH) of about 1 cm2, working at ultralow frequency (1–20 Hz), without any supported additional mass on its mobile electrode, and working even without a vacuum environment is reported. The prototype is especially suitable for environments with abundant low frequency motions such as wearable electronics. The proposed e-KEH consists of a capacitor with a finger-teeth interdigited comb structure. This greatly reduces the air damping effect, and thus the capacitance variation remains important regardless of the presence of air. With the new design, the energy transduced per cycle of excitation is no less than 33 times higher than the classic design within 10–40 Hz/2 gpeak, while is 85 times higher at 15 Hz/2 gpeak. An enclosed miniature ball combined with non-linear stoppers enables the oscillation of the movable electrode through impact-based frequency up-conversion mechanism, which is also improved by the low air damping. Thanks to this new design, a higher efficiency than the classic gap-closing comb structure is obtained, as a larger range of working frequency (1–180 Hz) in air. A maximum energy conversion of 450 nJ/cycle is obtained with a bias voltage of 45 V and an acceleration of 11 Hz, 3 gpeak. Working with a diode AC-DC rectifier, the proposed KEH is able to support up to 3 RFID communications within 16 s while operated at 11 Hz, 3 gpeak.

This paper describes a predictive and complete numeric model of a multi-mass and impact-coupled MEMS electrostatic kinetic energy harvester (e-KEH). A silicon resonator is coupled with elastic silicon beams (acting as a part of stoppers) and a miniature metallic ball. The model considers all these impacts as well as the electromechanical force and catches the frequency-up and spring-softening effects. More importantly, for the first time, it models accurately the evolving and non-linear squeeze-film air damping effect in a gap-closing transducer, which is induced by the large amplitude of displacement of the silicon mass. The predictions provided by the model are compared with experimental results, showing a good consistency. The key parameters of the KEH are analyzed with the proposed model, which can be of great help for further design optimization of similar devices. [2018-0174]

This paper reports a paper-based electrostatic kinetic energy harvester (e-KEH) implementing multilayered electret films based on electrospun nanofibrous material. It is the first time that a fully flexible electret-based e-KEH is reported. The proposed electret, PVDF-PTFD nanofibrous covered by Parylene C, has a faster stabilization of surface potential than a planar thin film of Parylene C, and a higher stability of charge storage. With a maximum force of 0.5 N and a 3-layer electret, the device capacitance increases from 25 pF to 100 pF during a pressing operation. Working with the optimal resistive load of 16 MΩ, the device pressed manually delivers a peak instantaneous power up to 45.6 μW and an average energy of 54 nJ/stroke, corresponding to a peak instantaneous power density of 7.3 μWcm-2 and an average energy density of 8.6 nJcm-2/stroke. Within 450 manual strokes, a 10-nF capacitor is charged up to 8.5 V by the prototype through a full-wave diode bridge. On a 1-μF capacitor, the energy delivery of 9.9 nJ/stroke has been obtained with a 10 Hz pressing movement excited by a vibrator with a maximum force of 0.5 N.

In this paper, electrospun piezoelectric PVDF-TrFE nanofibers were used for the fabrication of two types of flexible nanogenerator (NG) devices based on the direct piezoelectric effect, allowing the conversion of mechanical energy into electrical energy. The first one is composed of quite well aligned thin film nanofibers of about 35 μm and the second one is composed of random nanofibers of about 50 μm. The influence of the applied stress and strain rate on the output for both types of NG was studied. It is shown that the pulse peaks generated by NG increase with the applied mechanical strain frequency, the generated output is also proportional to the applied stress amplitude. The first NG loaded in bending mode can generate a maximum voltage of 270 mV. By connecting two devices in series/parallel, the voltage/current value could be multiplied by two. The second NG which was biased in compression mode using a shaker controlled by a force sensor, can generate a potential of about 7 V under 3.6 N applied force.

International audience; We report an energy-autonomous Radio Frequency IDentification (RFID) tag system which is powered by an electrostatic MEMS-based Vibration Energy Harvester (e-VEH). The VEH is designed specifically for the vibrations of low frequency around 10 Hz. An energy of 80 nJ/cycle can be delivered when the VEH is loaded with an optimal resistor and a bias of 20 V. An RFID chip is powered by the current released from a 1-μF capacitor, which is charged by the VEH through a diode rectifier. The read range of the tag is increased from 2.5 m (under batteryless mode) to 15 m when powered by the VEH working with an acceleration of 2 grms and 10 Hz. The energy of the VEH stored in the capacitor within 40 s can sustain up to 3 tag readings.

This letter reports the characterization procedure of a radio frequency identification (RFID) tag powered by a microelectromechanical system vibration energy harvester (VEH). The tag antenna and its matching interface to the RFID chip are designed with the help of an electromagnetic simulator. The energy provided by the VEH is stored in a reservoir capacitor and released through a mechanical switch to the tag. It is demonstrated that the tag can communicate with a reader at a distance up to 15 m when powered by the VEH working with an acceleration of 2 $g_{rms}$ and 100 Hz. The energy delivered by the VEH within 100 s can sustain up to six tag readings using the EPC Gen-2 Class-1 standard.

We report a hierarchical hexahedral geometry of interdigited-comb MEMS capacitor for electrostatic vibration energy harvesters (e-VEHs), where the air damping effect is greatly reduced while the capacitance variation remains important. Based on the same frequency up-conversion structure as in our previous design, the device with the new electrode geometry reaches a larger bandwidth (10∼180 Hz) in air compared to the classical gap-closing structure (80∼160 Hz). The energy extracted in air during each cycle of input excitation is 85 times higher than the classical design @15 Hz / 2 g peak (20 V), and is no less than 33 times higher within 10∼40 Hz.

Capturing the body's mechanical energy from the heart, lungs, and diaphragm can probably meet the requirements for in vivo applications of implantable biomedical devices. In this work, we present a novel contractile cardiomyocyte (CM)-driven biogenerator based on piezoelectric nanofibers (NFs) uniaxially aligned on a PDMS thin film. Flexible nanostructures interact with the CMs, as a physical cue to guide the CMs to align in a specific way, and create mechanical interfaces of contractile CMs and piezoelectric NFs. As such, the cellular construct features specific alignment and synchronous contraction, which realizes the maximal resultant force to drive the NFs to bend periodically. Studies on contraction mapping show that neonatal rat CMs self-assemble into a functional bio-bot film with well-defined axes of force generation. Consequently, the biogenerator produces an average voltage of 200 mV and current of 45 nA at the cell concentration of 1.0 million per ml, offering a biocompatible and scalable platform for biological energy conversion.

International audience; We report a 1-cm2 ultra-wideband MEMS electrostatic vibration energy harvester (e-VEH) that combines a frequency-up conversion system with a vertical electret layer obtained by corona discharge. At 2.0 grms, the device can harvest more than 1 μW from 59 to 148 Hz, and more than 0.5 μW from 14 to 152 Hz. Thanks to this new device, we demonstrate the self-starting power supply of an energy autonomous temperature sensor node with a data transmission beyond a distance of 10 m at 868 MHz.

International audience; This article proposes a silicon-based electrostatic kinetic energy harvester with an ultra-wide operating frequency bandwidth from 1 Hz to 160 Hz. This large bandwidth is obtained, thanks to a miniature tungsten ball impacting with a movable proof mass of silicon. The motion of the silicon proof mass is confined by nonlinear elastic stoppers on the fixed part standing against two protrusions of the proof mass. The electrostatic transducer is made of interdigited-combs with a gap-closing variable capacitance that includes vertical electrets obtained by corona discharge. Below 10 Hz, the e-KEH offers 30.6 nJ per mechanical oscillation at 2 grms, which makes it suitable for powering biomedical devices from human motion. Above 10 Hz and up to 162 Hz, the harvested power is more than 0.5 μW with a maximum of 4.5 μW at 160 Hz. The highest power of 6.6 μW is obtained without the ball at 432 Hz, in accordance with a power density of 142 μW/cm3. We also demonstrate the charging of a 47-μF capacitor to 3.5 V used to power a battery-less wireless temperature sensor node.

International audience; This paper reports for the first time a MEMS electrostatic vibration energy harvester (e-VEH) with corona-charged vertical electrets on its electrodes. The bandwidth of the 1-cm2 device is extended in low and high frequencies by nonlinear elastic stoppers. With a bias voltage of 46 V (electret@21 V + DC external source@25 V) between the electrodes, the RMS power of the device reaches 0.89 μW at 33 Hz and 6.6 μW at 428 Hz. The -3dB frequency band including the hysteresis is 223~432 Hz, the one excluding the hysteresis 88~166 Hz. We also demonstrate the charging of a 47 μF capacitor used for powering a wireless and autonomous temperature sensor node with a data transmission beyond 10 m at 868 MHz.

The interaction of sulfonated polystyrene (SPS) with cetyl trimethylammonium bromide (CTAB) and myristyl trimethylammonium bromide (MTAB) in aqueous solution was investigated. It was found that the solution viscosity increases rapidly at the molar ratio of CTAB/-SO3Na = 0.5 or MTAB/-SO3Na = 0.6 (the first viscosity maximum) and CTAB/-SO3Na = ∼1.5 or MTAB/-SO3Na = 2.0 (the second viscosity maximum). Both the first and the second viscosity maxima are related closely with the hydrophobic domains formed in solution, which can be detected using methyl orange as a spectral probe or N,N-dimethylamino flavone as fluorescent probe. In the higher concentration of [SPS], such as >0.05 M (-SO3Na unit), the SPS/CTAB solution converts to gel suddenly at CTAB/-SO3Na = ∼1.5–1.7 region, but with a further addition of CTAB or SPS, the gel collapses quickly. A term “micelle crosslinking” was proposed to explain the conversion of solution/gel and the reversible nature of gel ↔ solution.

Aquaporin-4 (AQP4) is a basolateral water channel in collecting duct principal cells and assembles into orthogonal array particles (OAPs), the size of which appears to depend on relative expression levels of AQP4 splice variants. Because the higher-order organization of AQP4 was perturbed by vasopressin in Brattleboro rats and phosphorylation sites have been identified on AQP4, we investigated whether vasopressin and forskolin (Fk) affect AQP4 assembly and/or expression in LLC-PK1cells stably transfected with the AQP4 splice variant M23, which is responsible for formation of OAPs, and/or the splice variant M1, which does not form OAPs. Our data show that [lys8]-vasopressin (LVP) and Fk treatment led to differential increases in expression levels of M23-AQP4 and M1-AQP4 that varied as a function of incubation time. At early time points ( day 1) expression of M1 was significantly stimulated (4.5-fold), over that of M23 (1.6-fold), but after 3 days the expression of M23 became predominant (4.1-fold) over that of M1 (1.9-fold). This pattern of stimulation was dependent on an intact AQP4 residue serine 111 and required protein synthesis. In cells expressing both M1 and M23 (M1/M23 ∼ 1), with small sized OAPs at the membrane, the LVP/Fk-induced stimulation of M23 was modified and mimicked that of M1 when expressed alone, suggesting a dominant role for M1. In Brattleboro kidney inner medulla, an 8-day chronic exposure to the vasopressin agonist (dDAVP) led to reduction in M1 and a significant increase in M23 immunoblot staining (M1/M23 = 2/3 → 1/4). These results indicate that AQP4 organization and expression are regulated by vasopressin in vivo and in vitro and demonstrate that the dominant role for M1 is restricted to a one-to-one interaction between AQP4 splice variants that regulates the membrane expression of OAPs.

Recent work1,2 indicates that the South China Sea is an ‘Atlantictype’ marginal basin of late Tertiary age. Magnetic anomalies in the eastern part of the sea are consistent with seafloor spreading directed approximately north–south1,2. We present here a new morphostructural study based on coupled seabeam mapping and single-channel seismic reflection profiling, which reveals dominant normal fault scarps, striking N50° E between 113 and 119° E longitude near the axis of this basin. Such a structural fabric implies a NW–SE spreading direction, at least in the 150–200-km-wide axial region of the South China Sea, and places new constraints on geodynamic models for the formation of this basin in the tectonic and palaeogeographic framework of South-East Asia and the South-West Pacific.