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Ferroelectric photovoltaic (FePV) materials are naturally considered a new type of solid-state optoelectronic memory conducting with high storage densities and nonvolatile states. This work investigates ferroelectric properties of Sc0.2Al0.8N thin film with a remnant polarization of ~122 μC/cm2 and researches the switchable FePV effect and photo-diode characteristics of two-terminal Sc0.2Al0.8N devices. When adopting a two-dimensional material MoTe2 to form heterostructure, both the photo absorption spectrum and the conductivity of ScAlN based two-terminal device would be promoted, resulting in the photocurrent at the level of μA/cm2. This work suggests ScAlN can provide a promising FePV implementation for constructing high-performance optoelectronics.

This article presents a high quality factor ( ${Q}$ ) load sensor based on Sc0.2Al0.8N/aluminum nitride (AlN)-on-silicon surface acoustic wave (SAW) resonator. Finite element method (FEM) analysis is performed to predict the resonance frequency and the wave propagation mode. A high- ${Q}$ of 7200 at the parallel resonance frequency ( ${f}_{p}$ ) of 447.50 MHz is measured for Sc0.2Al0.8N/AlN configured SAW resonator on a silicon substrate. Experimental values for variation of series resonance frequency ( ${\Delta } {f}_{s}$ ) and variation of ${f}_{p}$ ( ${\Delta } {f}_{p}$ ) are found to be −75.3 and −186.8 kHz with variation of applied force $({\Delta } \textit {F)} = 4.155$ N, operating in the analyzed range. The linear approximation of measured frequency variations under force is ${\Delta } {f}_{s}/{F} = -12.7$ kHz/N and ${\Delta } {f}_{p}/{F} = -46.2$ kHz/N. Moreover, the force sensitivities for this sensor are −28.4 and −103.2 ppm/N for ${f}_{s}$ and ${f}_{p}$ , respectively. This high- ${Q}$ scandium-doped AlN (ScAlN)/AlN-based SAW resonator exhibits high sensitivity, demonstrating that the structure can be used as load sensors in industrial applications such as manufacturing, medical, grocery, and automotive industries.

This paper presents a ScAlN/AlN-based MEMS piezoelectric accelerometer using the trapezoidal with corners (TWC) shaped cantilevers. The composite Sc0.2Al0.8N/AlN piezoelectric film is deposited on a silicon-on-insulator (SOI) substrate to improve the sensitivity of the piezoelectric accelerometer. The theoretical and FEM model is established to analyze the relationship between the cantilever stiffness and the piezoelectric parameters on the sensitivity and resonance frequency. The fabricated accelerometer includes a trapezoidal part, a rectangular part, and a silicon proof mass. The experimental results show that the sensitivity, minimum detectable signal (MDS), resolution, and resonant frequency of the proposed TWC shaped accelerometer are 7.95 mV/g, 1 mg, 1 mg, and 1290 Hz, respectively. The manufactured accelerometer exhibits good linearity up to 2 g (non-linearity ${T}=300$ K), the thermal noise of the fabricated accelerometer is lower than 94.7 nV/ $\surd $ Hz. Meanwhile, the charge amplifier circuit noise is about $1.97~\mu \text{V}/\surd $ Hz. The proposed TWC accelerometer is sensitive and suitable to sense vibration acceleration in low-frequency scenarios.

This article presents a Photoplethysmography (PPG) sensory system for continuous health monitoring. The PPG chip is fabricated using $0.35~\mu \text{m}$ standard CMOS technology and occupies 2.3 mm $\times$ 1.7 mm. The average power consumption of the receiver analog front-end (AFE) is $50.75~\mu \text{W}$ , the LED driver is power $29.3~\mu \text{W}$ . The consumed power is dramatically reduced due to the using of both low duty cycle for LED lighting and automatic light control (ALC). The PPG sensor has a low input noise current of 41.3 pA and can reject a DC photocurrent up to $24~\mu \text{A}$ because of the integrated background light cancelation (BLC) loop. 12-b SAR-ADC and Serial Peripheral Interface (SPI) are integrated for communication with MCU used for signal processing and results display. Readings of 9 subjects show mean absolute error (MAE) and standard deviation (SD) of 1.95±2.13 beats per minute (BPM), 6.00±4.18mmHg, and 6.13±3.93mmHg, for heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP), respectively.

A first-order ( S 1 ) Lamb wave resonator (LWR) with a trapezoid grooves configuration on the top surface of the aluminum nitride membrane between interdigital electrodes is proposed in this paper. Both the simulation and experiment results demonstrate that the k e f f 2 can be enhanced with the depth of the trapezoid grooves increasing. Meanwhile, the spurious modes can be suppressed by the trapezoid grooves. A 75% improvement on the k e f f 2 has been achieved in a 2.45 GHz S 1 mode LWR with trapezoid grooves with spurious modes free. The k e f f 2 reaches up to 5.47% without quality factor degradation.

The thin film bulk acoustic resonator (FBAR) has emerged as a promising choice for liquid sensors because of its high frequency and sensitivity. To investigate the potential of FBAR devices working as the liquid sensors, we study the operating law of FBAR in liquid environments and explore the different loading effects of liquid on the shear mode and longitudinal mode. By analyzing the device and liquid interactions, we modify the Mason model of FBAR in the liquid environment. Subsequently, the influence of the piezoelectric film with different tilt angles and liquids on the characteristics of FBAR is discussed. We also prepared Sc0.2Al0.8N film-based FBAR to confirm the influence of different liquid environments on the resonant performances. The results show that the frequency drift of FBAR in the shear mode is related to density and viscosity of liquid, and the frequency drift of FBAR in the longitudinal mode is related to bulk modulus and density of liquid. The resonant frequency of FBAR in the shear mode is more sensitive with glycerol solution than that of FBAR in the longitudinal mode. This work can provide a research basis for the application of FBAR liquid sensors.

The effective electromechanical coupling coefficient ( K eff 2 ) is one of the crucial parameters to evaluate the performance of resonators. However, the low effective electromechanical coupling coefficient K eff 2 limits the application of lamb wave resonators in filters. This work presents the impact of metallization rate on the K eff 2 of AlN Checker-mode resonators (CKMRs) by using the finite element analysis approach for the first time. Four types of piezoelectric effect excitation configurations are proposed with different electrode designs based on AlN CKMRs. The results show that CKMRs have the largest K eff 2 with the metallization rate of 0.25–0.31 for the top electrode. Meanwhile, when the metallization rate of the top electrode varies from 0.2 to 0.7, the K eff 2 of open CKMRs possess the most remarkable enhancement of about 235% of CKMRs. By properly optimizing the electrode design, CKMRs exhibit potential in commercial applications.

Broadband transducers occupy an important position in acoustic emission technology and its applications. The acoustic emission signals are usually caused by sudden local energy in materials or components, where the bandwidth needs to be wide. Therefore, it is inseparable from the broadband receiving transducer to extract a variety of useful information from the acoustic emission signal. Here, we present a broadband piezoelectric micromachined acoustic transducer by applying variable masses under different cantilever beams. The acoustic transducer operates in both the audible frequency band and ultrasound frequency band. The bandwidth is 2.54kHz and 37.1kHz when the sensor signal is attenuated by half (-6dB) in the primary and higher-order modes. Compared with previous transducers, the broadband transducer exhibits a flatter frequency response around the resonance region and a high output voltage in a wide frequency range. This is of great benefit to receive sound signals.

With the rapid development of microelectromechanical systems (MEMS), microphones need to be more miniaturized and integrated. This paper presents an AIN-based high sensitivity piezoelectric MEMS microphone (PMM) fabricated on a cavity silicon-on-insulator (CSOI) platform. The microphone consists of six trapezoidal piezoelectric cantilevers, where the fixed end of the beam is located in the center of the hexagonal working area. Through theoretical analysis and finite element method (FEM) simulation, we have demonstrated that the proposed structure has higher electro-acoustic conversion sensitivity than the reference device. The receiving sound pressure sensitivity of the designed device is −80.5 dB (re 1V/Pa). In addition, its near-field radiated sound pressure is 75.6 dB SPL under the excitation of 1Vrms.

Remarkable differences between the chemical compositions of the essential oils from three yellow Camellias were found, and the antioxidant and antimicrobial activities of the three oils were reported for the first time. Although yellow Camellia is a popular tea tree with golden flowers, there is insufficient information available about its volatile constituents and biological activity. In the present work, the essential oils from the leaves of Camellia tunghinensis, Camellia nitidissima and Camellia euphlebia were obtained by hydrodistillation. A total of 75, 56 and 55 constituents, accounting for approximately 86.9%, 77.5% and 84.5% of the oils of C. tunghinensis, C. nitidissima and C. euphlebia, respectively, were identified. GC/MS analysis showed that the principal components of the oil of C. tunghinensis were n-hexanal (17.2%), 2-pentylfuran (10.6%), phytone (7.5%) and geranylacetone (5.0%). The oil of C. nitidissima is rich in linalool (35.8%), phytol (7.9%), geranylacetone (7.3%) and methyl salicylate (6.8%), while phytol (58%), geranylacetone (5.6%) and n-hexanal (3.3%) are the major constituents of the oil of C. euphlebia. The antioxidant activities of the three oils were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) (ABTS) assays. The IC50 values of the oils varied from 42.82 to 164.98 µg/mL for DPPH and from 120.56 to 321.91 µg/mL for ABTS, which indicated that the three oils possess moderate antioxidant effects. Moreover, the antimicrobial activities of the oils were tested against four microorganisms (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa) by the disc diffusion method. Except for Pseudomonas aeruginosa, the tested microorganisms were sensitive to the oils, and inhibition zones from 12.1 to 24.3 mm were observed. The minimum inhibitory concentrations (MIC values) were determined to be 0.625–2.5 mg/mL, indicating the oils had weak antibacterial effects.

A low-power, high-gain, and low-noise analog front-end (AFE) for wearable photoplethysmography (PPG) acquisition systems is designed and fabricated in a 0.35 &mu, m CMOS process. A high transimpedance gain of 142 dB&Omega, and a low input-referred noise of only 64.2 pArms was achieved. A Sub-Hz filter was integrated using a pseudo resistor, resulting in a small silicon area. To mitigate the saturation problem caused by background light (BGL), a BGL cancellation loop and a new simple automatic gain control block are used to enhance the dynamic range and improve the linearity of the AFE. The measurement results show that a DC photocurrent component up-to-10 &mu, A can be rejected and the PPG output swing can reach 1.42 Vpp at THD &lt, 1%. The chip consumes a total power of 14.85 &mu, W using a single 3.3-V power supply. In this work, the small area and efficiently integrated blocks were used to implement the PPG AFE and the silicon area is minimized to 0.8 mm &times, 0.8 mm.

Three-dimensional self-supported cathode nanoarchitectures are the key to develop high-performance thin film lithium-ion microbatteries and flexible lithium-ion batteries. In this work, we have developed a facile “hydrothermal lithiation” strategy to prepare vertically aligned porous LiMn2O4 nanowall arrays, comprising highly crystallized spinel nanoparticles, on various conductive substrates without high temperature treatment. The “hydrothermal lithiation” can effectively convert Mn3O4 spinel nanowall arrays into LiMn2O4 spinel nanowall arrays without severe morphology change. The binder-free three-dimensional porous LiMn2O4 nanowall arrays exhibit high specific reversible capacity up to 131 mA h g−1 (or 0.29 mA h cm−2) as well as outstanding cycling stability and rate capability, making them promising as cathodes for both three-dimensional thin film lithium-ion microbatteries and flexible lithium-ion batteries. A flexible lithium-ion full cell is demonstrated by using LiMn2O4 nanowall arrays on carbon cloth as the cathode and Li4Ti5O12 nanowall arrays on carbon cloth as the anode. The flexible Li4Ti5O12//LiMn2O4 full cell device, employing three-dimensional nanoarchitectures for both cathode and anode, can deliver specific reversible capacities of 124.8 mA h g−1 (based on the weight of cathode material) at 1 C and 92.1 mA h g−1 at 20 C with excellent cycle performance. Our work demonstrates the great potential for flexible energy storage technology using low cost fabrication method of nanoarchitectures.

Monolayer MoS2 nanosheets (NSs) are promising anode materials for lithium-ion batteries because all redox reactions take place at the surface without lithium-ion diffusion limit. However, the expanded band gap of monolayer MoS2 NSs (∼1.8 eV) compared to their bulk counterparts (∼1.2 eV) and restacking tendency due to the van der Waals forces result in poor electron transfer and loss of the structure advantage. Here, a facile approach is developed to fabricate the MoS2-graphene aerogels comprising controlled three-dimensional (3D) porous architectures constructed by interconnected monolayer MoS2-graphene hybrid NSs. The robust 3D architectures combining with the monolayer feature of the hybrid NSs not only prevent the MoS2 and graphene NSs from restacking, but also enable fast electrode kinetics due to the surface reaction mechanism and highly conductive graphene matrix. As a consequence, the 3D porous monolayer MoS2-graphene composite aerogels exhibit a large reversible capacity up to 1200 mAh g(-1) as well as outstanding cycling stability and rate performance, making them promising as advanced anode materials for lithium-ion batteries.

Kinase non-catalytic C-lobe domain containing 1 (KNDC1) exists in dendrites, guanine nucleotide exchange factor complexes and neuronal cell bodies as a putative protein-protein interaction module that regulates a number of signaling pathways. Previous studies have demonstrated that the knockdown of KNDC1 delays human umbilical vein endothelial cell (HUVEC) senescence. However, the effect of KNDC1 overexpression on HUVEC function remains unclear. In the present study, an adenovirus vector carrying KNDC1 was constructed and then transfected into endothelial cells to observe cell senescence. Furthermore, the effect of KNDC1 overexpression on HUVEC senescence was investigated in vitro and the underlying molecular mechanism was investigated. Senescence-associated β-galactosidase staining was used to determine cellular senescence and reactive oxygen species (ROS) were monitored to detect the level of cell oxidative stress. The mRNA transcription level and protein expression were analyzed by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. The results demonstrated that KNDC1 overexpression possibly inhibited HUVEC activity and function and promoted HUVEC senescence. Mechanistic studies demonstrated that KNDC1 triggered a p53-ROS positive feedback loop, which serves a crucial role in regulating senescence. In conclusion, to the best of the authors' knowledge, this is the first time that KNDC1-adenovirus vector inhibition of HUVEC proliferation by activating the p53 signaling pathway has been reported. Theoretically, the results of the present study also support KNDC1 as a therapeutic target for future anti-senescence.

This paper presents a low-power analog front-end (AFE) photoplethysmography (PPG) sensor fabricated in 0.35 µm CMOS process. The AFE amplifies the weak photocurrent from the photodiode (PD) and converts it to a strong voltage at the output. In order to decrease the power consumption, the circuits are designed in subthreshold region; so the total biasing current of the AFE is 10 µ A. Since the large input DC photocurrent is a big issue for the PPG sensing circuit, we apply a DC photocurrent rejection technique by adding a DC current-cancellation loop to reject the large DC photocurrent up to 10 µA. In addition, a pseudo resistor is used to reduce the high-pass corner frequency below 0.5 Hz and Gm-C filter is adapted to reject the out-of-band noise higher than 16 Hz. For the whole sensor, the amplifier chain can achieve a total gain of 140 dBμ and an input integrated noise current of 68.87 pA rms up to 16 Hz.

Highlights: • Self-supported LiMn{sub 2}O{sub 4} nanorod arrays are prepared on the Pt substrates. • LiMn{sub 2}O{sub 4} nanorod array cathode exhibits a large areal capacity of 0.25 mAh cm{sup −2}. • LiMn{sub 2}O{sub 4} nanorod array cathode exhibits good cycle performance and rate capability. • LiMn{sub 2}O{sub 4} nanorod arrays are potential cathodes for 3D microbatteries. - Abstract: Although three-dimensional (3D) microbatteries represent great advantage compared to their two-dimensional counterparts, the fabrication of 3D cathode is still a challenge, which holds back the further development of 3D microbatteries. In this work, we present a novel approach for fabrication of LiMn{sub 2}O{sub 4} nanorod arrays as 3D cathode for microbatteries. α-MnO{sub 2} nanotube arrays are firstly grown on the Pt substrate as the template, and LiMn{sub 2}O{sub 4} nanorod arrays are then prepared by lithiation of α-MnO{sub 2} nanotube arrays in molten salt followed by 800 °C annealing in air. In the half cell test, the 3D LiMn{sub 2}O{sub 4} nanorod arrays exhibit both high gravimetric capacity (∼130 mAh g{sup −1}) and areal capacity (∼0.25 mAh cm{sup −2}), while maintaining good cycling stability and rate capability. The facile synthesis and superior electrochemical performance of the three-dimensional LiMn{sub 2}O{sub 4} cathodemore » make it promising for application in microbatteries.« less

Nanocrystalline LiMn 2 O 4 /graphene nanosheets nanocomposite has been successfully synthesized by a one-step hydrothermal method without post-heat treatment. In the nanocomposite, LiMn 2 O 4 nanoparticles of 10–30 nm in size are well crystallized and homogeneously anchored on the graphene nanosheets. The graphene nanosheets not only provide a highly conductive matrix for LiMn 2 O 4 nanoparticles but also effectively reduce the agglomeration of LiMn 2 O 4 nanoparticles. The nanocrystalline LiMn 2 O 4 /graphene nanosheets nanocomposite exhibited greatly improved electrochemical performance in terms of specific capacity, cycle performance, and rate capability compared with the bare LiMn 2 O 4 nanoparticles. The superior electrochemical performance of the nanocrystalline LiMn 2 O 4 /graphene nanosheets nanocomposite makes it promising as cathode material for high-performance lithium-ion batteries.

Nanocrystalline LiMn2O4/graphene nanosheet (GNS) composite is hydrothermally prepared by dispersing GNS in H2O followed by addition of KMnO4 and LiOH (autoclave, 180 °C, 5 h).