Performance enhancement of armchair graphene nanoribbon resonant tunneling diode using V-shaped potential well

We study the electron transport in armchair graphene nanoribbon (AGNR) resonant tunneling diode (RTD) using square and V-shaped potential well profiles. We use non-equilibrium Green’s function formalism to analyze the transmission and I-V characteristics. Results show that an enhancement in the peak current (Ip ) can be obtained by reducing the well width (Ww ) or barrier width (Wb ). As Ww decreases, Ip shifts to a higher peak voltage (Vp ), while there is almost no change in Vp with decreasing Wb . It is gratifying to note that there is an enhancement in Ip by about 1.6 times for a V-shaped well over a square well. Furthermore, in the case of a V-shaped well, the negative differential resistance occurs in a shorter voltage range, which may beneficial for ultra-fast switching and high-frequency signal generation. Our work anticipates the suitability of graphene, having better design flexibility, to develop ideally 2D RTDs for use in ultra-dense nano-electronic circuits and systems.

Vibration Energy Harvester Based on Torsionally Oscillating Magnet

Most of the miniaturized electromagnetic vibrational energy harvesters (EVEHs) are based on oscillating proof mass suspended by several springs or a cantilever structure. Such structural feature limits the miniaturization of the device’s footprint. This paper presents an EVEH device based on a torsional vibrating magnet over a stack of flexible planar coils. The torsional movement of the magnet is enabled by microfabricated silicon torsional springs, which effectively reduce the footprint of the device. With a size of 1 cm × 1 cm × 1.08 cm, the proposed EVEH is capable of generating an open-circuit peak-to-peak voltage of 169 mV and a power of 6.9 μW, under a sinusoidal excitation of ±0.5 g (g = 9.8 m/s2) and frequency of 96 Hz. At elevated acceleration levels, the maximum peak-to-peak output voltage is 222 mV under the acceleration of 7 g (±3.5 g).

An Experimental Study on Efficient Piezoelectric Coupled Beams and Corresponding Piezoelectric Bricks

In view of the low output power density of the existing footstep harvesters, two pairs of distinctive L-shaped beams and the corresponding piezoelectric brick models are developed to improve the utilization efficiency of the piezoelectric patches bonded on the beams. A theory model of the aforesaid L-shaped beam is established to analyze its dynamic performance. Two pairs of L-shaped beams and corresponding piezoelectric brick specimens are customized. The influences of some factors on the output voltage and average power from piezoelectric patches of aforesaid piezoelectric bricks are tested and analyzed. Numerical computation based on the theory model of L-shaped beam is conducted to extend the study on the electric output performances of the proposed piezoelectric bricks. Experiment and simulation results indicate that the peak-to-peak voltage and average power can reach up to 376 V (0.15 V/mm3) and 94.72 mW (37.89 μW/mm3) for a piezoelectric patch with a dimension of 50 mm × 50 mm × 1 mm of brick specimens. This research provides novel piezoelectric bricks to harvest footstep energy and obtains some instructive conclusions for the practical design of the piezoelectric brick with ideal energy harvesting efficiency and cost-effectiveness.

Energy harvesting performance of an EDLC power generator based on pure water and glycerol mixture: analytical modeling and experimental validation

A liquid droplet oscillating between two plane electrodes was visualized, and the electrical power generation based on the reverse-electrowetting-on-dielectric (REWOD) phenomenon was measured. For the upper plate, a hydrophobic surface treated by PTFE was used, and the lower plate was tested using the hydrophilic surface properties of ITO glass. To analyze the dynamic behavior of an oscillating liquid bridge, a modeling study was carried out using the phase field method based on the finite element method. The dynamic contact angle of the oscillating liquid bridge was modeled based on advancing and receding contact angles. The variable interfacial areas between the liquid and solid surfaces were calculated and agreed well with the experimental results within a 10% error band. Furthermore, experimental and analytical studies were carried out to examine the REWOD energy harvesting characteristics of the glycerol-water mixtures in various concentrations. As a result, the peak voltage output was obtained at a specific concentration of the glycerol mixture, and the power density of the oscillating liquid bridge at this point was up to 2.23 times higher than that of pure water.

Time-Domain Pulse Waveform Correction for Pulsed Electric Field Measurement in Microwave Cable with Frequency-Dependent Loss

This paper presents a method that corrects pulse waveforms distorted by the frequency-dependent loss of microwave cables in measuring pulsed electric fields (PEFs). Because the distortion resulting from the microwave cable disrupts accurate PEF measurements, the distorted pulse should be corrected for precise PEF effect testing. The proposed correction method is achieved by a transfer function that is determined by ABCD parameters calculated from the scattering parameters of the cable. A 10-m microwave cable is tested to validate the proposed method, where the input pulse is a 2-ns sine pulse of a single cycle. Here, the output pulse, scattering parameters, and cable resistance are measured. These measurement results are used to represent the transfer function in MATLAB for the proposed correction method. The test results show that the corrected pulse obtained from the transfer function has an error of 4.5% in the peak-to-peak voltage and an error of 0.8% in the bipolar pulse width compared to the reference input pulse. The errors of PEF measurement decrease dramatically by using the proposed correction method. Moreover, the correction method is validated for various pulse durations, pulse shapes, and cable types.

An Electret/Hydrogel-Based Tactile Sensor Boosted by Micro-Patterned and Electrostatic Promoting Methods with Flexibility and Wide-Temperature Tolerance

With the rising demand for wearable, multifunctional, and flexible electronics, plenty of efforts aiming at wearable devices have been devoted to designing sensors with greater efficiency, wide environment tolerance, and good sustainability. Herein, a thin film of double-network ionic hydrogel with a solution replacement treatment method is fabricated, which not only possesses excellent stretchability (>1100%) and good transparency (>80%), but also maintains a wide application temperature range (−10~40 °C). Moreover, the hydrogel membrane further acts as both the flexible electrode and a triboelectric layer, with a larger friction area achieved through a micro-structure pattern method. Combining this with a corona-charged fluorinated ethylene propylene (FEP) film, an electret/hydrogel-based tactile sensor (EHTS) is designed and fabricated. The output performance of the EHTS is effectively boosted by 156.3% through the hybrid of triboelectric and electrostatic effects, which achieves the open-circuit peak voltage of 12.5 V, short-circuit current of 0.5 μA, and considerable power of 4.3 μW respectively, with a mentionable size of 10 mm × 10 mm × 0.9 mm. The EHTS also demonstrates a stable output characteristic within a wide range of temperature tolerance from −10 to approximately 40 °C and can be further integrated into a mask for human breath monitoring, which could provide for a reliable healthcare service during the COVID-19 pandemic. In general, the EHTS shows excellent potential in the fields of healthcare devices and wearable electronics.

Broadband vibration energy harvester based on nonlinear magnetic force and rotary pendulums

A broadband vibration energy harvester based on nonlinear magnetic force and rotary pendulums is proposed in this paper. The harvester is mainly composed of a magnetoelectric transducer and a rotary pendulum fixed with four permanent magnets. In order to improve the working bandwidth of the harvester, two pairs of permanent magnets are added in the middle of the rotary pendulum by using magnetic nonlinearity. The mechanical - magnetic - electrical analytical model of the harvester is established, and the theoretical value obtained by the model is basically consistent with the experimental value. The results show that the harvester has a strong nonlinearity through the magnetic force. When the acceleration is 0.4 g, some typical testing results are as follows: the resonant frequency is 19 Hz, maximum peak-peak voltage is 94.1 V, half power bandwidth is 15.8 Hz, center frequency is 26.9 Hz, and the ratio of half power bandwidth to the center frequency is 58.73 %.

Bone Mineral Density Attenuation in Obstructive Sleep Apnea by Derived Computed Tomography Screening

The association between obstructive sleep apnea (OSA) and bone mineral density (BMD) is poorly elucidated with contradictory findings. We retrospectively explored the association between OSA and BMD by examining abdominal computed tomography (CT) vertebrae images using clinical information. We included 315 subjects (174 with OSA and 141 without OSA) who performed at least two CT scans (peak voltage of 120 kV). Bone mineral density was attenuated in those with OSA and increased age. BMD attenuation was not associated with the apnea–hypopnea score, nocturnal oxygen saturation, or arousal index. A multivariate linear regression indicated that OSA is associated with BMD attenuation after controlling for age, gender, and cardiovascular diseases. Here, we report that OSA is associated with BMD attenuation. Further studies are required to untangle the complex affect of OSA on BMD loss and possible clinical implication of vertebra depressed fracture or femoral neck fracture.

Abstract 14407: Effect of Initial Defibrillation on Chest Compression Artifact in the ECG

Introduction: Chest compressions (CCs) during CPR cause electrical artifacts in the ECG. Prior work has found that the severity of CC artifact, quantified by the signal-to-noise ratio (SNR), affects the diagnostic sensitivity of defibrillator algorithms designed to detect shockable rhythms during CCs. Whether SNR is altered by defibrillation is unknown. We therefore compared SNR before and after defibrillation shocks. Methods: We evaluated patients with out-of-hospital cardiac arrest who received at least 1 defibrillation shock, had subsequent ventricular fibrillation (VF), and had a calculable SNR before and after initial shock. We measured the CC artifact during VF before and after the initial shock (and up to 3 subsequent shocks) using CC amplitude and SNR. CC amplitude was defined as the median peak-to-peak voltage of the ECG during CCs. SNR was calculated as the log ratio of the power of the CC-free VF signal to the power of the estimated noise caused by CC artifact (Figure). Differences in medians before and after the first 4 shocks were evaluated using Wilcoxon signed-rank test with Bonferroni correction (alpha = 0.0125). Results: A total of 192 patients had a calculable SNR during VF before and after initial shock. Of these, the median CC amplitude decreased after the initial shock (0.93 vs. 0.75 mV, p<0.001), and SNR improved (-2.30 vs. -1.07 dB, p=0.004). In contrast to the initial shock, both CC amplitude and SNR did not differ significantly before and after shock 2 (n=107), shock 3 (n=54), or shock 4 (n=32). Conclusion: Measures of CC artifact in the ECG were greater before initial shock than afterward. This could potentially be due to changes in CC characteristics, variations in physical perturbation of the defibrillator electrodes, degradation of VF over time, or effects of tissue electroporation on paddle conductivity and noise. These findings may have implications for selection of decision thresholds in algorithms to detect shockable rhythm during CCs.

A Tuning Fork Frequency Up-Conversion Energy Harvester

In this paper, a novel tuning fork structure for self-frequency up-conversion is proposed. The structure has an in-phase vibration mode and an anti-phase vibration mode. The in-phase vibration mode is used to sense the environment vibration, and the anti-phase vibration mode is used for energy conversion and power generation. The low-frequency energy collection and the high-frequency energy conversion can be achieved simultaneously. Theoretical and experimental results show that the tuning fork frequency up-conversion energy harvester has excellent performance. This structure provides the energy harvester with excellent output power in a low-frequency vibration environment. At the resonant frequency of 7.3 Hz under 0.7 g acceleration, the peak voltage is 41.8 V and the peak power is 8.74 mW. The tuning fork frequency up-conversion energy harvester causes the humidity sensor to work stably. The structure has the potential to power wireless sensor nodes or to be used as a small portable vibration storage device, especially suitable for the monitoring of the environment related to human movement.