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Harvesting sustainable energy resources from surrounding environments to power small electronic devices and systems has attracted massive research attention. Herein, we develop a novel technology to harvest light energy to self-power and simultaneously sense mechanical acceleration in a monolithic structure. When the photonic gate is illuminated the operation mode of the device changes from conventional mode to light harvesting and self-powered operation. The light illumination provides a gradient of majority carrier concentration on the top semiconductor layer, generating a lateral photovoltage, which is the output voltage of the sensor. Under acceleration, the mechanical inertial force induces stress in the sensor material leading to the change of mobility of the charge carriers, which shifts their diffusion rate, and hence changes the gradient of the majority carriers and the lateral photovoltage. The sensitivity at 480 lx light illumination was measured to be 107 μ V / g , while it was approximately 30 μ V / g under the ambient light illumination without any electrical power source. In addition, the acceleration sensitivity is tunable by controlling parameters of the photonic gate such as light power, light spot position and light wavelength. The integration of sensing and powering functions into a monolithic platform proposed in this work eliminates the requirement of external power sources and offers potential solutions for wireless, independent, remote, and battery-free sensing devices and systems.

Respiration signals are a vital sign of life. Monitoring human breath provides critical information for health assessment, diagnosis, and treatment for respiratory diseases such as asthma, chronic bronchitis, and emphysema. Stretchable and wearable respiration sensors have recently attracted considerable interest toward monitoring physiological signals in the era of real time and portable healthcare systems. This review provides a snapshot on the recent development of stretchable sensors and wearable technologies for respiration monitoring. The article offers the fundamental guideline on the sensing mechanisms and design concepts of stretchable sensors for detecting vital breath signals such as temperature, humidity, airflow, stress and strain. A highlight on the recent progress in the integration of variable sensing components outlines feasible pathways towards multifunctional and multimodal sensor platforms. Structural designs of nanomaterials and platforms for stretchable respiration sensors are reviewed.

Semiconductor nanowires are widely considered as the building blocks that revolutionized many areas of nanosciences and nanotechnologies. The unique features in nanowires, including high electron transport, excellent mechanical robustness, large surface area, and capability to engineer their intrinsic properties, enable new classes of nanoelectromechanical systems (NEMS). Wide bandgap (WBG) semiconductors in the form of nanowires are a hot spot of research owing to the tremendous possibilities in NEMS, particularly for environmental monitoring and energy harvesting. This article presents a comprehensive overview of the recent progress on the growth, properties and applications of silicon carbide (SiC), group III‐nitrides, and diamond nanowires as the materials of choice for NEMS. It begins with a snapshot on material developments and fabrication technologies, covering both bottom‐up and top‐down approaches. A discussion on the mechanical, electrical, optical, and thermal properties is provided detailing the fundamental physics of WBG nanowires along with their potential for NEMS. A series of sensing and electronic devices particularly for environmental monitoring is reviewed, which further extend the capability in industrial applications. The article concludes with the merits and shortcomings of environmental monitoring applications based on these classes of nanowires, providing a roadmap for future development in this fast‐emerging research field., Wide bandgap semiconductor nanowires with unique properties and advanced fabrication/integration technologies set a new class of nanosensing and electronic applications. Implementation of these smart devices such as gas sensors, photodetectors, wearable devices, strain sensors, and energy harvesters into environmental monitoring systems offers promising solutions for critical environmental challenges.

Improving and optimizing the processes for transfer printing have the potential to further enhance capabilities in heterogeneous integration of various sensing materials on unconventional substrates for implantable and stretchable electronic devices in biosensing, diagnostics, and therapeutic applications. An advanced transfer printing method based on sacrificial layer engineering for silicon carbide materials in stretchable electronic devices is presented here. In contrast to the typical processes where defined anchor structures are required for the transfer step, the use of a sacrificial layer offers enhances versatility in releasing complex microstructures from rigid donor substrates to flexible receiver platforms. The sacrificial layer also minimizes twisting and wrinkling issues that may occur in free‐standing microstructures, thereby facilitating printing onto flat polymer surfaces (e.g., polydimethylsiloxane). The experimental results demonstrate that transferred SiC microstructures exhibit good stretchability, stable electrical properties, excellent biocompatibility, as well as promising sensing‐functions associated with a high level of structural perfection, without any cracks or tears. This transfer printing method can be applied to other classes of wide bandgap semiconductors, particularly group III‐nitrides and diamond films epitaxially grown on Si substrates, thereby serving as the foundation for the development and possible commercialization of implantable and stretchable bioelectronic devices that exploit wide bandgap materials.

Tuning the natural frequency of a resonator is an innovative approach for the implementation of mechanical resonators in a broad range of fields such as timing applications, filters or sensors. The conventional electrothermal technique is not favorable towards large tuning range because of its reliance on metallic heating elements. The use of metallic heaters could limit the tuning capability due to the mismatch in thermal expansion coefficients of materials forming the resonator. To solve this drawback, herein, the design, fabrication, and testing of a highly-doped SiC bridge resonator that excludes the use of metallic material as a heating element has been proposed. Instead, free-standing SiC structure functions as the mechanical resonant component as well as the heating element. Through the use of the Joule heating effect, a frequency tuning capability of almost∆f/fo≈80% has been demonstrated. The proposed device also exhibited a wide operating frequency range from 72.3kHz to 14.5kHz. Our SiC device enables the development of highly sensitive resonant-based sensors, especially in harsh environments.

Stretchable and wearable sensor technology has attracted significant interests and created high technological impact on portable healthcare and smart human-machine interfaces. Wearable electromechanical systems are an important part of this technology that has recently witnessed tremendous progress toward high-performance devices for commercialization. Over the past few years, great attention has been paid to simultaneously enhance the sensitivity and stretchability of the electromechanical sensors toward high sensitivity, ultra-stretchability, low power consumption or self-power functionalities, miniaturisation as well as simplicity in design and fabrication. This work presents state-of-the-art advanced materials and rational designs of electromechanical sensors for wearable applications. Advances in various sensing concepts and structural designs for intrinsic stretchable conductive materials as well as advanced rational platforms are discussed. In addition, the practical applications and challenges in the development of stretchable electromechanical sensors are briefly mentioned and highlighted.

Straw amendment and plant root exudates modify the quality and quantities of soil dissolved organic matter (DOM) and then manipulate the fractions of soil selenium (Se) and its bioavailability. Two typical soils with distinct pH were selected to investigate the effect of different contributors on DOM-Se in soil. The mechanisms relying on the variation in DOM characteristics (quality, quantity and composition) were explored by UV-Vis, ATR-FTIR and 3D-EEM. Straw amendment significantly (p 0.05) suppressed the selenate bioavailability. The reduction in wheat Se content was greater in krasnozems than in Lou soil, as more HA fraction appeared in krasnozems. The root exudates of wheat mainly elevated the low molecular hydrophilic compounds (Hy) in soil, which contributed to the SOL-Hy-Se fractions and thus grain Se in soils (p 0.01). However, straw amendment promoted DOM transforming from small molecules (Hy and FA) to aromatic large molecules (HA), when accompanied with the reduction and retention of Se associated with these molecules. As a result, selenium bioavailability and toxicity reduced with DOM amendment and DOM-Se transformation.

This paper reports on a platform for monolithic integration of piezoelectric and piezoresistive devices on a single chip using the ScAlN/3C-SiC/Si heterostructure. Surface acoustic wave devices with an electromechanical coupling of 3.2% and an out-of-band rejection as high as 18 dB are demonstrated using the excellent piezoelectric properties of ScAlN and low acoustic loss of 3C-SiC. Additionally, a large piezoresistive effect in the low-doped n-type 3C-SiC(100) thin film has been observed, which exceeds the previously reported values in any SiC thin films. The growth of the n-type 3C-SiC thin film was performed using the low pressure chemical vapor deposition technique at 1250 °C and the standard micro-electro-mechanical systems process is used for the fabrication of 3C-SiC piezoresistors. The piezoresistive effect was measured using the bending beam method in different crystallographic orientations. The maximum gauge factor is –47 for the longitudinal [100] orientation. Using the longitudinal and transverse gauge factors for different crystallographic orientations, the fundamental piezoresistive coefficients of the low-doped n-type 3C-SiC thin film are measured to be π 11 = ( − 14.5 ± 1.3 ) × 10 − 11 Pa−1, π 12 = ( 5.5 ± 0.5 ) × 10 − 11 Pa−1, and π 44 = ( − 1.7 ± 0.7 ) × 10 − 11 Pa−1.

Silicon carbide (SiC)‐based microsystems are promising alternatives for silicon‐based counterparts in a wide range of applications aiming at conditions of high temperature, high corrosion, and extreme vibration/shock. However, its high resistance to chemical substances makes the fabrication of SiC particularly challenging and less cost‐effective. To date, most SiC micromachining processes require time‐consuming and high‐cost SiC dry‐etching steps followed by metal wet etching, which slows down the prototyping and characterization process of SiC devices. This work presents a lithography and etching‐free microfabrication for 3C‐SiC on insulator‐based microelectromechanical systems (MEMS) devices. In particular, a direct laser ablation technique to replace the conventional lithography and etching processes to form functional SiC devices from 3C‐SiC‐on‐glass wafers is used. Utilizing a single line‐cutting mode, both metal contact shapes and SiC microstructures can be patterned simultaneously with a remarkably fast speed of over 20 cm s−1. As a proof of concept, several SiC microdevices, including temperature sensors, strain sensors, and microheaters, are demonstrated, showing the potential of the proposed technique for rapid and reliable prototyping of SiC‐based MEMS.

Selenite and selenate are two main selenium (Se) forms absorbed by plants. The comparative effects of selenite and/or selenate on Se uptake and translocation in plants in spite of their coexistence in the environment are still unclear. Therefore, tomato (Solanum lycopersicum L.) seedlings were grown in a hydroponic solution with exogenous selenite, selenate, or selenite and selenate mixed, and Se concentrations in shoots, roots, and xylem sap were measured after harvest. Results showed that selenite (> 0.1 mg Se L−1) could cause phytotoxicity more easily than selenate (> 1 mg Se L−1) under hydroponic conditions. And the absorbability rate of tomato to selenate was higher than that to selenite when Se application level was 0.0175–0.2998 mg L−1, while the opposite result was observed in other Se concentrations. More Se accumulated in roots and Se(VI) in the xylem sap decreased when both Se forms supplied. This study demonstrated that the difference between selenite and selenate on Se uptake and translocation in tomatoes depended on exogenous Se concentration. And selenite could inhibit the absorption and translocation of selenate when supplied with both Se forms.

Due to the two-dimensional effect of selenium (Se) to health, which form of Se is most effective for increasing the bioaccessible Se content in P. ostreatus and whether these products have potential health risks are worth considering. Three Se supplements were applied at different application rates into substrates for cultivating P. ostreatus. The total content and speciation of Se in P. ostreatus fruit bodies were analyzed, and the bioaccessibility of Se was determined via an in vitro physiologically based extraction test (PBET). Results showed that P. ostreatus had the highest utilization efficiency with selenite, followed by Se yeast and selenate. Organic Se (46%-90%) was the major Se speciation in P. ostreatus regardless applied Se species. Although the Se bioaccessibility of the gastrointestinal digestion of P. ostreatus was high (70%-92%), the estimated daily intake and target hazard quotient values are all within the safe ranges. Se-enriched P. ostreatus can be safely used as a dietary source of Se for increasing Se intake.

This paper reports on the piezoresistive effect in p-type 3C-SiC thin film mechanical sensing at cryogenic conditions. Nanothin 3C-SiC films with a carrier concentration of 2 × 1019 cm−3 were epitaxially grown on a Si substrate using the LPCVD process, followed by photolithography and UV laser engraving processes to form SiC-on-Si pressure sensors. The magnitude of the piezoresistive effect was measured by monitoring the change of the SiC conductance subjected to pressurizing/depressurizing cycles at different temperatures. Experimental results showed a relatively stable piezoresistive effect in the highly doped 3C-SiC film with the gauge factor slightly increased by 20% at 150 K with respect to that at room temperature. The data was also in good agreement with theoretical analysis obtained based on the charge transfer phenomenon. This finding demonstrates the potential of 3C-SiC for MEMS sensors used in a large range of temperatures from cryogenic to high temperatures.

This paper presents an analytical solution for the Joule heating problem of a segmented wire made of two materials with different properties and suspended as a bridge across two fixed ends. The paper first establishes the one-dimensional (1D) governing equations of the steady-state temperature distribution along the wire with the consideration of heat conduction and free-heat convection phenomena. The temperature coefficient of resistance of the constructing materials and the dimension of the each segmented wires were also taken into account to obtain analytical solution of the temperature. COMSOL numerical solutions were also obtained for initial validation. Experimental studies were carried out using copper and nichrome wires, where the temperature distribution was monitored using an IR thermal camera. The data showed a good agreement between experimental data and the analytical data, validating our model for the design and development of thermal sensors based on multisegmented structures.

A better understanding of the benefits of selenium (Se) fertilization to alleviate the toxicity of mercury (Hg) on plants and of the underlying mechanisms involved in Hg stress is important for the remediation of soils contaminated by Hg. This study is aimed to explore the effects of the application of selenite to alleviate the toxicity of Hg in soils to plants and related mechanisms involved in this process. The chemical (Hg uptake of pak choi), biological (root and shoot length, root and shoot weight) and physiological effects (antioxidant enzyme activities, non-enzymatic antioxidant contents (proline) and lipid peroxidation products (malondialdehyde)) produced over plants by the application of different doses of Hg and Se to soil has been investigated through a pot experiment, which was conducted with exposure to different dosages of mercuric chloride (0, 1.0, 2.0, and 3.0 mg/kg soil) and sodium selenite (0, 0.5, 1.0, and 2.5 mg/kg soil). Results indicated that single high Hg treatment (3.0 mg/kg Hg) resulted in significantly increase in Hg uptake by plants (P 0.01), thus the growth of pak choi was inhibited. However, the Se application at 1.0 and 2.5 mg/kg led to significantly alleviated Hg uptake by plants (P 0.05). Meanwhile, the low Se (at 0.5 and 1.0 mg/kg) applied to soil induced significantly improvement the growth of pak choi (P 0.05) by elevating the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione peroxidase (GSH-Px) enzymes and the content of chlorophyll (SPAD value) as well as suppressed the lipid peroxidation products contents (MDA) and proline. Results collectively indicated that applied Se played an important role in promoting the detoxification of Hg and growth of pak choi under oxidative stress. Notably, this role may only be significant when Se application at the appropriate concentration (≤ 1.0 mg/kg).

This paper presents a simple, rapid and cost-effective wire bonding technique for single crystalline silicon carbide (3C–SiC) MEMS devices. Utilizing direct ultrasonic wedge–wedge bonding, we have demonstrated for the first time the direct bonding of aluminum wires onto SiC films for the characterization of electronic devices without the requirement for any metal deposition and etching process. The bonded joints between the Al wires and the SiC surfaces showed a relatively strong adhesion force up to approximately 12.6–14.5 mN and excellent ohmic contact. The bonded wire can withstand high temperatures above 420 K, while maintaining a notable ohmic contact. As a proof of concept, a 3C–SiC strain sensor was demonstrated, where the sensing element was developed based on the piezoresistive effect in SiC and the electrical contact was formed by the proposed direct-bonding technique. The SiC strain sensor possesses high sensitivity to the applied mechanical strains, as well as exceptional repeatability. The work reported here indicates the potential of an extremely simple direct wire bonding method for SiC for MEMS and microelectronic applications.

This work presents the fabrication, mechanical strength characterization, and cell culture demonstration of a high aspect ratio silicon carbide (SiC) membrane. Optimizations in the deposition and fabrication make an ultra-high aspect ratio up to 20,000 SiC membranes with high fracture strength possible. Utilizing the superior properties of SiC material, the ultra-thin SiC membrane is a promising for cell culture/stretching devices, enabling very short optical accesses. The biocompatibility of the SiC membrane was confirmed with the 3T3 fibroblasts cell viability rate of 92.7%, in which the cells flattened and elongated their morphology while maintaining a strong adhesion to the SiC surface.

This chapter presents the fundamentals of thermoresistive effect in different SiC morphologies including single-crystalline cubic SiC, polycrystalline and amorphous SiC. The thermocapacitive and thermoelectric effects are also summarised. In addition, recent advances in the characterisation of the thermoelectrical effect in SiC single and double layers with a heterostructure will be discussed. Other aspects of temperature effect on the electrical properties of SiC are mentioned.

This work presents a conversion free p-type 4H silicon carbide (4H-SiC) four-terminal strain sensor utilizing a large Hall offset voltage in a symmetric four-terminal configuration. Upon the application of mechanical strain, a high sensitivity of 209 mV/A/ppm was obtained. The strain sensor also exhibited good repeatability and linearity with a significantly large offset voltage in the induced strain ranging from 0 to 334ppm. Coupled these performances with the excellent mechanical strength, electrical conductivity, thermal stability, and chemical inertness of the SiC material, the proposed 4H-SiC strain sensor is promising for stress/strain monitoring for harsh operating environments with high signal-to-noise ratio.

This chapter presents the future prospect of SiC MEMS thermoelectrical sensing devices in terms of the development of new platform and integration capability of SiC with other materials for high-temperature applications. The chapter also describes the possibility of using the thermoelectrical effect in SiC for possible applications in sensing systems, including resonant sensors. Challenges and opportunities for the development of SiC thermal devices in high-temperature applications will also be discussed.

There are several parameters representing the detection capability and efficiency of SiC sensors towards practical applications such as temperature detectors, flow sensors, convective-based accelerometers and gyroscopes. This chapter presents a number of desirable parameters for SiC thermal sensors at high temperatures. These important features include, but are not limited to, the sensitivity, response time and linearity.

This chapter describes the approaches for the growth of high-quality silicon carbide. The doping methods for n-type and p-type SiC with the inclusion of selective doping are presented. Various fabrication strategies are introduced, including wet etching and oxidation. Fundamental properties of Ohmic and Schottky contacts to SiC are included. This chapter also gives brief examples of fabrication processes to achieve standard MEMS structures such as cantilevers and membranes.

This chapter presents the general background on silicon carbide as a functional semiconductor for sensors operating in harsh environments. The fundamental stacking orders of different SiC polytypes with common growth methods and conditions are introduced, with a focus on cubic silicon carbide (3C-SiC) and hexagonal silicon carbide (e.g. 4H-SiC and 6H-SiC). This chapter also introduces the thermoelectrical effect in SiC with respect to sensing properties at high temperatures. The importance of SiC materials with a wide range of applications in harsh environments will be mentioned.

This chapter describes the influence of the design and fabrication processes on the performance of SiC thermal devices. The chapter first discusses the influence of various substrates on the sensitivity of SiC nanofilms. The impact of doping types and doping levels will be presented. The dependence of the performance of SiC thermal devices on the material morphologies will be mentioned. Finally, this chapter presents the capability of growing SiC nanoscale films and the dependence of the temperature coefficient of resistance on the thickness of SiC films.

The global movement towards lower carbon economies and distributed energy requires the realisation of improved energy generation methods. Tri-generation is a method of optimising the thermal efficiency of energy generation through waste heat recapturing and can simultaneously provide heating, cooling and electrical output to meet building energy demands. A meta-analysis was conducted to analyse the performance of various prime movers utilised in tri-generation applications. Through this study it was determined that the efficiency of tri-generation and combined cycles can be optimised through a hybridisation of prime movers.

The piezoresistive effect in silicon nanowires (SiNWs) has attracted a great deal of interest for NEMS devices. Most of the piezoresistive SiNWs reported in the literature were fabricated using the bottom up method or top down processes such as electron beam lithography (EBL). Focused ion beam (FIB), on the other hand, is more compatible with CMOS integration than the bottom up method, and is simpler and more capable of fabricating very narrow Si nanostructures compared to EBL and photolithography. Taking the advantages of FIB, this paper presents for the first time the piezoresistive effect of p-type SiNWs fabricated using focused ion beam implantation and wet etching. The SiNWs were locally amorphized by Ga+ ion implantation, selectively wet-etched, and thermally annealed at 700 °C. A relatively large gauge factor of approximately 47 was found in the annealed SiNWs, indicating the potential of using the piezoresistive effect in top-down fabricated SiNWs for developing NEMS sensors.

This article reports the first results on the strain-induced pseudo-Hall effect in single crystal 3C-SiC(111) four-terminal devices. The impact of crystal orientation and the direction of strain on this effect has been presented. A single crystal p-type 3C-SiC(111) was grown by low pressure chemical vapor deposition and four-terminal devices were fabricated using conventional photolithography and dry etching processes. It has been observed that the pseudo-Hall effect in p-type 3C-SiC(111) is the same in [110] and [11] crystal orientations and is smaller than the pseudo-Hall effect of 3C-SiC(100) four-terminal devices due to the defects associated with the growth of 3C-SiC(111).

This communication reports for the first time, the impact of device geometry on the stress-dependent offset voltage of single crystal p-type 3C–SiC four terminal devices. Single crystal p-type 3C–SiC(100) was grown by low pressure chemical vapor deposition and three different device geometries (cross, rectangle and square) were fabricated using the conventional photolithography and dry etching processes. It was observed that the stress-dependent offset voltage of the devices strongly depends upon the device geometry and it can be increased by almost 100% by just selecting the appropriate device geometry. We also found that as the device is rotated within the (100) crystal plane its stress sensitivity varies from ≈0 to 9 × 10−11 Pa−1.

This paper reports on the thermoresistive properties of graphite on paper (GOP). A negative temperature coefficient of resistance (TCR) from −2900 to −4400 ppm K−1 was observed for the GOP. This negative and large TCR is attributed to an increase in the thermionic emission current over a low potential barrier with increasing temperature. The potential barrier was found to be 33 meV between the graphite grains. The paper also demonstrates the use of the GOP in a highly sensitive (0.83 mV (m s−1)−0.8 mW−1) GOP-based anemometer, indicating strong feasibility of using this material for low-cost and sensitive thermal sensing applications.

Micromachined membranes are promising platforms for cell culture thanks to their miniaturization and integration capabilities. Possessing chemical inertness, biocompatibility, and integration, silicon carbide (SiC) membranes have attracted great interest toward biological applications. In this paper, we present the batch fabrication, mechanical characterizations, and cell culture demonstration of robust ultrathin epitaxial deposited SiC membranes. The as-fabricated ultrathin SiC membranes, with an ultrahigh aspect ratio (length/thickness) of up to 20 000, possess high a fracture strength up to 2.95 GPa and deformation up to 50 μm. A high optical transmittance of above 80% at visible wavelengths was obtained for 50 nm membranes. The as-fabricated membranes were experimentally demonstrated as an excellent substrate platform for bio-MEMS/NEMS cell culture with the cell viability rate of more than 92% after 72 h. The ultrathin SiC membrane is promising for in vitro observations/imaging of bio-objects with an extremely short optical access.

To exploit the plant byproducts from selenium (Se) biofortification and reduce environmental risk of inorganic Se fertilizer, pot experiment was conducted in this study. The effects of Se-enriched wheat (Triticum aestivum L.) straw (WS + Se) and pak choi (Brassica chinensis L.) (P + Se) amendment on organo-selenium speciation transformation in soil and its bioavailability was evaluated by pak choi uptake. The Se contents of the cultivated pak choi in treatments amended with the same amount of Se-enriched wheat straw and pak choi were 1.7 and 9.7 times in the shoots and 2.3 and 6.3 times in the roots compared with control treatment. Soil respiration rate was significantly increased after all organic material amendment in soil (p

This letter reports a giant opto-piezoresistive effect in p-3C-SiC/p-Si heterostructure under visible-light illumination. The p-3C-SiC/p-Si heterostructure has been fabricated by growing a 390 nm p-type 3C-SiC on a p-type Si substrate using the low pressure chemical vapor deposition (LPCVD) technique. The gauge factor of the heterostructure was found to be 28 under a dark condition; however, it significantly increased to about −455 under illumination of 635 nm wavelength at 3.0 mW/cm2. This gauge factor is over 200 times higher than that of commercial metal strain gauge, 16 times higher than that of 3C-SiC thinfilm, and approximately 5 times larger than that of bulk Si. This enhancement of the gauge factor was attributed to the opto-mechanical coupling effect in p-3C-SiC/p-Si heterostructure. The opto-mechanical coupling effect is the amplified effect of the photoconductivity enhancement and strain-induced band structure modification in the p-type Si substrate. These findings enable extremely high sensiti...

This paper presents for the first time a p-type 4H silicon carbide (4H-SiC) van der Pauw strain sensor by utilizing the strain induced effect in four-terminal devices. The sensor was fabricated from a 4H-SiC (0001) wafer, using a 1 μm thick p-type epilayer with a concentration of 1018 cm−3. Taking advantage of the four-terminal configuration, the sensor can eliminate the need for resistance-to-voltage conversion which is typically required for two-terminal devices. The van der Pauw sensor also exhibits an excellent repeatability and linearity with a significantly large output voltage in induced strain ranging from 0 to 334 ppm. Various sensors aligned in different orientations were measured and a high sensitivity of 26.3 ppm−1 was obtained. Combining these performances with the excellent mechanical strength, electrical conductivity, thermal stability, and chemical inertness of 4H-SiC, the proposed sensor is promising for strain monitoring in harsh environments.

Developing flexible pressure sensors is of high interest in soft skin and tactile sensing applications. Here we demonstrate a simple approach to fabricating a sensitive resistive pressure sensor using carbon nanotube (CNT) micro-yarns as a pressure sensing element which is constructed on a stretchable acrylic elastomer. The sensor showed a high sensitivity of −0.86 Ω/kPa and a fast response time of 100 ms. Different to the longitudinal piezoresistive effect of micro-yarns, the high pressure sensitivity of the sensor was achieved owing to the compressibility of the micro-yarn in the direction perpendicular to the yarn axis. The sensor was also able to monitor finger pressure in real-time, demonstrating its potential for tactile sensing applications.

Flow sensing in hostile environments is of increasing interest for applications in the automotive, aerospace, and chemical and resource industries. There are thermal and non-thermal approaches for high-temperature flow measurement. Compared to their non-thermal counterparts, thermal flow sensors have recently attracted a great deal of interest due to the ease of fabrication, lack of moving parts and higher sensitivity. In recent years, various thermal flow sensors have been developed to operate at temperatures above 500 °C. Microelectronic technologies such as silicon-on-insulator (SOI), and complementary metal-oxide semiconductor (CMOS) have been used to make thermal flow sensors. Thermal sensors with various heating and sensing materials such as metals, semiconductors, polymers and ceramics can be selected according to the targeted working temperature. The performance of these thermal flow sensors is evaluated based on parameters such as thermal response time, flow sensitivity. The data from thermal flow sensors reviewed in this paper indicate that the sensing principle is suitable for the operation under harsh environments. Finally, the paper discusses the packaging of the sensor, which is the most important aspect of any high-temperature sensing application. Other than the conventional wire-bonding, various novel packaging techniques have been developed for high-temperature application.

Selenite (Se (IV)) and selenate (Se (IV)) have recently been demonstrated to be equally effective in inhibiting mercury (Hg) phytotoxicity to plants. This assertion is still unclear. In this study, we aimed to explore the potential effects of Se species (Se

In this paper, we propose an extended navigation framework for autonomous mobile robots in dynamic environments using a reinforcement learning algorithm. The main idea of the proposed algorithm is to provide the mobile robots the relative position and motion of the surrounding objects to the robots, and the safety constraints such as minimum distance from the robots to the obstacles, and a learning model. We then distribute the mobile robots into a dynamic environment. The mobile robots will automatically learn to adapt to the environment by their own experienced through the trial-and-error interaction with the surrounding environment. When the learning phase is completed, the mobile robots equipped with our proposed framework are able to navigate autonomously and safely in the dynamic environment. The simulation results in a simulated environment shows that, our proposed navigation framework is capable of driving the mobile robots to avoid dynamic obstacles and catch up dynamic targets, providing the safety for the surrounding objects and the mobile robots.

This paper presents an active disturbance rejection rejection control design for integrated guidance and control missile based on sliding mode control and extended state observer. The integrated model is formulated as a block-strict-feedback nonlinear system, in which modeling errors, unmodeled non-linearities, target maneuvers, etc. are viewed as unknown uncertainties. The nonlinear control law is designed based on backstepping and sliding mode control (SMC) techniques. Based on the principle of active disturbance rejection control (ADRC), enhanced feedback linearization (FL) based control law is implemented for the IGC model using the estimates generated by an extended state observer (ESO). The stability analysis of the closed-loop system is also conducted. Simulation results show that, small miss distances and smooth missile trajectories are achieved, and the system is robust against system uncertainties and external disturbances.

Flexible multifunctional electronic devices are of high interest for a wide range of applications including thermal therapy and respiratory devices in medical treatment, safety equipment, and structural health monitoring systems. This paper reports a scalable and efficient strategy of manufacturing a polyacrylonitrile-carbon nanotube-polyacrylonitrile (PAN-CNT-PAN)robust flexible platform for multifunctional electronic devices including flexible heaters, temperature sensors, and flexible thermal flow sensors. The key advantages of this platform include low cost, porosity, mechanical robustness, and electrical stability under mechanical bending, enabling the development of fast-response flexible heaters with a response time of ≈1.5 s and relaxation time of ≈1.7 s. The temperature-sensing functionality is also investigated with a range of temperature coefficient of resistances from −650 to −900 ppm K−1. A flexible hot-film sensing concept is successfully demonstrated using PAN-CNT-PAN with a high sensitivity of 340 mV (m s−1)−1. The sensitivity enhancement of 50% W−1 is also observed with increasing supply power. The low cost, porosity, versatile, and robust properties of the proposed platform will enable the development of multifunctional electronic devices for numerous applications such as flexible thermal management, temperature stabilization in industrial processing, temperature sensing, and flexible/wearable devices for human healthcare applications.

There is an increasing demand for the development and integration of multifunctional sensing modules into power electronic devices that can operate in high temperature environments. Here, the authors demonstrate the tunable thermoresistance of p‐type 4H–SiC for a wide temperature range from the room temperature to above 800 K with integrated flow sensing functionality into a single power electronic chip. The electrical resistance of p‐type 4H–SiC is found to exponentially decrease with increasing temperature to a threshold temperature of 536 K. The temperature coefficient of resistance (TCR) shows a large and negative value from −2100 to −7600 ppm K−1, corresponding to a thermal index of 625 K. From the threshold temperature of 536–846 K, the electrical resistance shows excellent linearity with a positive TCR value of 900 ppm K−1. The authors successfully demonstrate the integration of p–4H–SiC flow sensing functionality with a high sensitivity of 1.035 μA(m s−1)−0.5 mW−1. These insights in the electrical transport of p–4H–SiC aid to improve the performance of p–4H–SiC integrated temperature and flow sensing systems, as well as the design consideration and integration of thermal sensors into 4H–SiC power electronic systems operating at high temperatures of up to 846 K.

This letter reports for the first time the strain dependence of the offset voltage in p-type 3C-SiC van der Pauw square device. The p-type 3C-SiC thin film was epitaxially grown on a p-type Si(100) wafer using low pressure chemical vapor deposition followed by a conventional photolithography and dry etch processes, forming four-terminal van der Pauw device. The influence of applied tensile and compressive strain on the offset voltage of the van der Pauw device was investigated using the bending beam method. Experimental results showed that the offset voltage of the device is significantly changed by applied compressive and tensile strain, indicating the feasibility of using this effect for mechanical sensing applications. The sensitivity of the device to the applied strain has been found to be 70 (mV/A)/ppm.

article i nfo Here we report estimates of crustal thickness and Poisson's ratios for northern Vietnam, based on teleseismic receiver function analysis of observations from a dense broadband seismic array. The seismic array comprised of 24 stations distributed evenly over northern Vietnam, from whose records we examined 190 teleseismic events of Mw > 5.5 for the period 2006-2008. Using the radial receiver functions calculated from teleseismic records at individual stations, the optimum crustal thickness and Vp/Vs (where Vp and Vs are the velocities of P- and S-waves, respectively) ratio beneath each station were determined using the H-κ (where H is crustal thickness and κ is defined as the Vp/Vs ratio) stacking algorithm. Determined values of crustal thickness range from 26.5 km to 36.4 km, with an average of 31.0 ± 2.1 km. The simple pattern of variation of crustal thick- ness in the northeastern region of the study area, with a mean of ~31 km, suggests that the sector belongs to the craton of the South China block. A highly variable crustal thickness is found over the northwestern region of northern Vietnam, ranging from ~29.5 km to ~36.4 km, implying that complex tectonic processes have taken place in this region. The thinnest crust is found in the Red River Delta, where it ranges from 26.5 km to 30.4 km, which is suggestive of a recent rifting process. The determinations of crustal thickness show a good linear correlation with Bouguer gravity anomalies. Lower values of Poisson's ratio in the northeastern and Red River Delta sectors suggest a more felsic crust, and larger values in the northwestern sector suggest lithospheric extension in the Song Da depression. The findings enhance our understanding of the geotectonic architecture of the northern Vietnam region.