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The integration of micro- and nanoelectronics into or onto biomedical devices can facilitate advanced diagnostics and treatments of digestive disorders, cardiovascular diseases, and cancers. Recent developments in gastrointestinal endoscopy and balloon catheter technologies introduce promising paths for minimally invasive surgeries to treat these diseases. However, current therapeutic endoscopy systems fail to meet requirements in multifunctionality, biocompatibility, and safety, particularly when integrated with bioelectronic devices. Here, we report materials, device designs, and assembly schemes for transparent and stable cubic silicon carbide (3C-SiC)-based bioelectronic systems that facilitate tissue ablation, with the capability for integration onto the tips of endoscopes. The excellent optical transparency of SiC-on-glass (SoG) allows for direct observation of areas of interest, with superior electronic functionalities that enable multiple biological sensing and stimulation capabilities to assist in electrical-based ablation procedures. Experimental studies on phantom, vegetable, and animal tissues demonstrated relatively short treatment times and low electric field required for effective lesion removal using our SoG bioelectronic system.

The trend of globalization leads to an increased need for international freight transportation and accelerates the development of the global logistics industry. This paper aims to study logistics service providers' current status and strategies in central Vietnam. The study data sample was collected through a questionnaire form, responded by 488 companies outsourcing logistics services. The findings indicate a direction for the Central Vietnam authorities to follow in implementing the ideal investment prioritization and the appropriate regulations for improving its logistics industry. This study enriches the literature by investigating logistics study's current status and prospects in a transitional economy. It also offers invaluable information and implications for local providers, government authorities, and foreign logistic service providers interested in Central Vietnam's logistics industry.

It is critical to investigate the charge carrier gradient generation in semiconductor junctions with an asymmetric configuration, which can open a new platform for developing lateral photovoltaic and self-powered devices. This paper reports the generation of a charge carrier gradient in a 3C-SiC/Si heterojunction with an asymmetric electrode configuration. 3C-SiC/Si heterojunction devices with different electrode widths were illuminated by laser beams (wavelengths of 405, 521, and 637 nm) and a halogen bulb. The charge carrier distribution along the heterojunction was investigated by measuring the lateral photovoltage generated when the laser spot scans across the 3C-SiC surface between the two electrodes. The highest lateral photovoltage generated is 130.58 mV, measured in the device with an electrode width ratio of 5 and under 637 nm wavelength and 1000 μW illumination. Interestingly, the lateral photovoltage was generated even under uniform illumination at zero bias, which is unusual for the lateral photovoltage, as it can only be generated when unevenly distributed photogenerated charge carriers exist. In addition, the working mechanism and uncovered behavior of the lateral photovoltaic effect are explained based on the generation and separation of electron-hole pairs under light illumination and charge carrier diffusion theory. The finding further elaborates the underlying physics of the lateral photovoltaic effect in nano-heterojunctions and explores its potential in developing optoelectronic sensors.

Hydrogel actuators displaying programmable shape transformations promise to be core components in future biomedical and soft robotic devices. However, current hydrogel actuators have shortcomings, including poor mechanical properties, slow response, and lack of shape reprogrammability, which limit their practical applications . Existing molecular designs offer limited efficiency in synergistically addressing these issues in a single hydrogel system. Herein, we propose a strategy to develop hydrogel actuators with muscle-mimetic aligned microfibrillar morphology, combining thermoinduced microphase separation and mechanical alignment. The key to our design is the introduction of metal–phenolic complexes, which not only induce irreversible sol–gel transition via the concentrated coordinate ions above lower critical solution temperature (LCST) but also fix the alignment of bundle network due to dynamic network rearrangement. Our design concept is observed to simultaneously achieve excellent mechanical properties (tensile strength ≈ 1.27 MPa, toughness ≈ 2.0 MJ m–3) and ultrafast actuation (40.1% thermal contraction as short as 1 s), which is a long-lasting challenge in the field. In addition, the dynamic hydrogels can be reprogrammed into spiral, helical, and biomimetic actuators. This work opens new opportunities to realize real-world applications for smart hydrogels as soft machines by fundamentally breaking the current property limit.

Background and Purpose: The AFFINITY trial (Assessment of Fluoxetine in Stroke Recovery) reported that oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and seizures. After trial medication was ceased at 6 months, survivors were followed to 12 months post-randomization. This preplanned secondary analysis aimed to determine any sustained or delayed effects of fluoxetine at 12 months post-randomization. Methods: AFFINITY was a randomized, parallel-group, double-blind, placebo-controlled trial in adults (n=1280) with a clinical diagnosis of stroke in the previous 2 to 15 days and persisting neurological deficit who were recruited at 43 hospital stroke units in Australia (n=29), New Zealand (4), and Vietnam (10) between 2013 and 2019. Participants were randomized to oral fluoxetine 20 mg once daily (n=642) or matching placebo (n=638) for 6 months and followed until 12 months after randomization. The primary outcome was function, measured by the modified Rankin Scale, at 6 months. Secondary outcomes for these analyses included measures of the modified Rankin Scale, mood, cognition, overall health status, fatigue, health-related quality of life, and safety at 12 months. Results: Adherence to trial medication was for a mean 167 (SD 48) days and similar between randomized groups. At 12 months, the distribution of modified Rankin Scale categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio, 0.93 [95% CI, 0.76–1.14]; P =0.46). Compared with placebo, patients allocated fluoxetine had fewer recurrent ischemic strokes (14 [2.18%] versus 29 [4.55%]; P =0.02), and no longer had significantly more falls (27 [4.21%] versus 15 [2.35%]; P =0.08), bone fractures (23 [3.58%] versus 11 [1.72%]; P =0.05), or seizures (11 [1.71%] versus 8 [1.25%]; P =0.64) at 12 months. Conclusions: Fluoxetine 20 mg daily for 6 months after acute stroke had no delayed or sustained effect on functional outcome, falls, bone fractures, or seizures at 12 months poststroke. The lower rate of recurrent ischemic stroke in the fluoxetine group is most likely a chance finding. Registration: URL: http://www.anzctr.org.au/ ; Unique identifier: ACTRN12611000774921.

Giant piezoresistive effect enables the development of ultrasensitive sensing devices to address the increasing demands from hi-tech applications such as space exploration and self-driving cars. The discovery of the giant piezoresistive effect by optoelectronic coupling leads to a new strategy for enhancing the sensitivity of mechanical sensors, particularly with light from light-emitting diodes (LEDs). This paper reports on the piezoresistive effect in a 3C-SiC/Si heterostructure with a bonded LED that can reach a gauge factor (GF) as high as 18 000. This value represents an approximately 1000 times improvement compared to the configuration without a bonded LED. This GF is one of the highest GFs reported to date for the piezoresistive effect in semiconductors. The generation of carrier concentration gradient in the top thin 3C-SiC film under illumination from the LED coupling with the tuning current contributes to the modulation of the piezoresistive effect in a 3C-SiC/Si heterojunction. In addition, the feasibility of using different types of LEDs as the tools for modulating the piezoresistive effect is investigated by evaluating lateral photovoltage and photocurrent under LED's illumination. The generated lateral photovoltage and photocurrent are as high as 14 mV and 47.2 μA, respectively. Recent technologies for direct bonding of micro-LEDs on a Si-based device and the discovery reported here may have a significant impact on mechanical sensors.

This article researches current practices of several Vietnamese universities to fulfill their third mission. Analyzing results of major activities (such as technology transfer, research commercialization, and entrepreneurship) in 9 universities in the North of Vietnam from 2013 to 2018, the article identifies the limitations and suggests a number of governance policies to support universities in fulfilling their third mission in Vietnam’s current context. Keywords: Third Mission, University, Entrepreneurial University, Technology Transfer, Commercialization.

Wearable and implantable bioelectronics have experienced remarkable progress over the last decades. Bioelectronic devices provide seamless integration between electronics and biological tissue, offering unique functions for healthcare applications such as real-time and online monitoring and stimulation. Organic semiconductors and silicon-based flexible electronics have been dominantly used as materials for wearable and implantable devices. However, inherent drawbacks such as low electronic mobility, particularly in organic materials, instability, and narrow band gaps mainly limit their full potential for optogenetics and implantable applications. In this context, wide-band-gap (WBG) materials with excellent electrical and mechanical properties have emerged as promising candidates for flexible electronics. With a significant piezoelectric effect, direct band gap and optical transparency, and chemical inertness, these materials are expected to have practical applications in many sectors such as energy harvesting, optoelectronics, or electronic devices, where lasting and stable operation is highly desired. Recent advances in micro/nanomachining processes and synthesis methods for WBG materials led to their possible use in soft electronics. Considering the importance of WBG materials in this fast-growing field, the present paper provides a comprehensive Review on the most common WBG materials, including zinc oxide (ZnO) for II–VI compounds, gallium nitride (GaN) for III–V compounds, and silicon carbide (SiC) for IV–IV compounds. We first discuss the fundamental physical and chemical characteristics of these materials and their advantages for biosensing applications. We then summarize the fabrication techniques of wide-band-gap semiconductors, including how these materials can be transferred from rigid to stretchable and flexible substrates. Next, we provide a snapshot of the recent development of flexible WBG materials-based wearable and implantable devices. Finally, we conclude with perspectives on future research direction.

This article presents the design and characterization of a direct current (dc) sensor utilizing the Hall effect in AlGaN/GaN 2-D electron gas (2DEG) four-terminal devices and a flux concentrator. The sensor was fabricated from an AlGaN/GaN/Si wafer grown by metal-organic chemical vapor deposition. The sensor exhibited excellent linearity and repeatability with a high Hall voltage under the primary current ranging from −5 to 5 A. The sensitivity of the sensor was measured to be 0.26 (V/A)/A at 20 °C and independent of ambient temperature up to 200 °C. The obtained result is greater than that of other reported Hall effect-based current sensors. The high sensitivity and thermal stability at varying temperatures are attributed to the high electron mobility, wide bandgap, and stability of carrier density in 2DEG. Combining these factors with the excellent mechanical strength, electrical conductivity, and chemical inertness of GaN, the proposed sensor is promising for current monitoring in a wide range of operation temperatures.

Analysis of temporal patterns of high-dimensional time-series water quality data is essential for pollution management worldwide. This study has applied dynamic factor analysis (DFA) and cluster analysis (CA) to analyze time-series water quality data monitored at the five stations installed along the La Buong river in Southern Vietnam. Application of the DFA identified two types of temporal patterns, one of the run-off driven parameters (total suspended solid (TSS), turbidity, and iron) and the other of diffuse source pollution. The association of the variables like BOD

Electrical neuron stimulation holds promise for treating chronic neurological disorders, including spinal cord injury, epilepsy, and Parkinson’s disease. The implementation of ultrathin, flexible electrodes that can offer noninvasive attachment to soft neural tissues is a breakthrough for timely, continuous, programable, and spatial stimulations. With strict flexibility requirements in neural implanted stimulations, the use of conventional thick and bulky packages is no longer applicable, posing major technical issues such as short device lifetime and long-term stability. We introduce herein a concept of long-lived flexible neural electrodes using silicon carbide (SiC) nanomembranes as a faradic interface and thermal oxide thin films as an electrical barrier layer. The SiC nanomembranes were developed using a chemical vapor deposition (CVD) process at the wafer level, and thermal oxide was grown using a high-quality wet oxidation technique. The proposed material developments are highly scalable and compatible with MEMS technologies, facilitating the mass production of long-lived implanted bioelectrodes. Our experimental results showed excellent stability of the SiC/silicon dioxide (SiO 2 ) bioelectronic system that can potentially last for several decades with well-maintained electronic properties in biofluid environments. We demonstrated the capability of the proposed material system for peripheral nerve stimulation in an animal model, showing muscle contraction responses comparable to those of a standard non-implanted nerve stimulation device. The design concept, scalable fabrication approach, and multimodal functionalities of SiC/SiO 2 flexible electronics offer an exciting possibility for fundamental neuroscience studies, as well as for neural stimulation–based therapies.

Recently, wearable electronics for health monitoring have been demonstrated with considerable benefits for early-stage disease detection. This article reports a flexible, bending-insensitive, bio-compatible and lightweight respiration sensor. The sensor consists of highly oriented carbon nanotube (HO-CNT) films embedded between electro-spun polyacrylonitrile (PAN) layers. By aligning carbon nanotubes between the PAN layers, the sensor exhibits a high sensitivity towards airflow (340 mV/(m/s)) and excellent flexibility and robustness. In addition, the HO-CNT sensor is insensitive to mechanical bending, making it suitable for wearable applications. We successfully demonstrated the attachment of the sensor to the human philtrum for real-time monitoring of the respiration quality. These results indicate the potential of HO-CNT flow sensor for ubiquitous personal health care applications.

Quantum dots (QDs) were suggested a decade ago as a means of spectral decoy to divert rocket attacks from flying objects such as satellites but have not yet found industrial applications. A possible reason is that these advanced nanomaterials are unstable in the long-Term under the forces exhibited on a flying object and the nanoparticles might agglomerate to form larger microparticles, which have a different, unwanted spectral footprint. This work proposes an on-board (in situ) real-Time synthesis of quantum dots on a satellite as a result of an interdisciplinary innovation that combines nanomaterial chemistry, heating and mixing with batch microfluidics, and microfabrication of a miniaturized chip. We employed a microchip as the in situ reaction chamber due to its capability of fast, compact synthesis. The implementation of the space micro-reactor, on the other hand, leads to other fundamental challenges that need to be solved such as robust pump-free fluid motion and quick synthesis of quantum dots in less than 180 s which is equivalent to the typical time a rocket needs to reach the satellite from the ground. Additionally, quantum dots need to be tailored in the type of material and size to replicate the spectral signal of the to-be-protected space asset while the synthesis process needs to be robust and resilient to work reliably and automatically under the demanding conditions of a flying object. In this study, we selected cadmium selenide (CdSe) and lead selenide (PbSe) as the materials of choice. Our synthesis process aims to simplify and tailor CdSe and PbSe quantum dots to match the above demands. The produced quantum dots were characterized by their wavelength emission spectra and high-Angle annular dark-field scanning transmission electron microscopy (HAADF STEM) images. Results show that both CdSe and PbSe quantum dots have been successfully synthesized within a maximum of 10 minutes. While the chosen CdSe-based synthesis was unable to reach IR-emitting sizes within several minutes, we managed to meet all other research targets. The synthesized PbSe QDs were able to reach the mock-spectrum and could produce an emission wavelength peak from 1200 to 1400 nm. This work finally provides insights into the limits of batch synthesis in a microfabricated nanodot chip, such as the need to improve reproducibility and enhance particle growth. Based on this learning, we propose a self-priming flow microchip synthesis that can capitalize on mixing as a key asset to overcome those limits.

Background: Trials of fluoxetine for recovery after stroke report conflicting results. The Assessment oF FluoxetINe In sTroke recoverY (AFFINITY) trial aimed to show if daily oral fluoxetine for 6 months after stroke improves functional outcome in an ethnically diverse population.Methods: AFFINITY was a randomised, parallel-group, double-blind, placebo-controlled trial done in 43 hospital stroke units in Australia (n=29), New Zealand (four), and Vietnam (ten). Eligible patients were adults (aged ≥18 years) with a clinical diagnosis of acute stroke in the previous 2–15 days, brain imaging consistent with ischaemic or haemorrhagic stroke, and a persisting neurological deficit that produced a modified Rankin Scale (mRS) score of 1 or more. Patients were randomly assigned 1:1 via a web-based system using a minimisation algorithm to once daily, oral fluoxetine 20 mg capsules or matching placebo for 6 months. Patients, carers, investigators, and outcome assessors were masked to the treatment allocation. The primary outcome was functional status, measured by the mRS, at 6 months. The primary analysis was an ordinal logistic regression of the mRS at 6 months, adjusted for minimisation variables. Primary and safety analyses were done according to the patient's treatment allocation. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000774921.Findings: Between Jan 11, 2013, and June 30, 2019, 1280 patients were recruited in Australia (n=532), New Zealand (n=42), and Vietnam (n=706), of whom 642 were randomly assigned to fluoxetine and 638 were randomly assigned to placebo. Mean duration of trial treatment was 167 days (SD 48·1). At 6 months, mRS data were available in 624 (97%) patients in the fluoxetine group and 632 (99%) in the placebo group. The distribution of mRS categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio 0·94, 95% CI 0·76–1·15; p=0·53). Compared with patients in the placebo group, patients in the fluoxetine group had more falls (20 [3%] vs seven [1%]; p=0·018), bone fractures (19 [3%] vs six [1%]; p=0·014), and epileptic seizures (ten [2%] vs two [Interpretation: Oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and epileptic seizures. These results do not support the use of fluoxetine to improve functional outcome after stroke.Funding: National Health and Medical Research Council of Australia.

Utilizing harvesting energy to power sensors has been becoming more critical in the current age of the Internet of Things. In this paper, we propose a novel technology using a monolithic 3C-SiC/Si heterostructure to harvest photon energy to power itself and simultaneously sense the surrounding temperature. The 3C-SiC/Si heterostructure converts photon energy into electrical energy, which is manifested as a lateral photovoltage across the top material layer of the heterostructure. Simultaneously, the lateral photovoltage varies with the surrounding temperature, and this photovoltage variation with temperature is used to monitor the temperature. We characterized the thermoresistive properties of the 3C-SiC/Si heterostructure, evaluated its energy conversion, and investigated its performance as a light-harvesting self-powered temperature sensor. The resistance of the heterostructure gradually drops with increasing temperature with a temperature coefficient of resistance (TCR) ranging from more than -3500 to approximately -8200 ppm/K. The generated lateral photovoltage is as high as 58.8 mV under 12 700 lx light illumination at 25 °C. The sensitivity of the sensor in the self-power mode is as high as 360 μV·K

Asymptomatic transmission was found to be the Achilles' heel of the symptom-based screening strategy, necessitating the implementation of mass testing to efficiently contain the transmission of COVID-19 pandemic. However, the global shortage of molecular reagents and the low throughput of available realtime PCR facilities were major limiting factors.A novel semi-nested and heptaplex (7-plex) RT-PCR assay with melting analysis for detection of SARS-CoV-2 RNA has been established for either individual testing or 96-sample pooled testing. The complex melting spectrum collected from the heptaplex RT-PCR amplicons was interpreted with the support of an artificial intelligence algorithm for the detection of SARS-CoV-2 RNA. The analytical and clinical performance of the semi-nested RT-PCR assay was evaluated using RNAs synthesized in-vitro and those isolated from nasopharyngeal samples.The LOD of the assay for individual testing was estimated to be 7.2 copies/reaction. Clinical performance evaluation indicated a sensitivity of 100% (95% CI: 97.83-100) and a specificity of 99.87% (95% CI: 99.55-99.98). More importantly, the assay supports a breakthrough sample pooling method, which makes possible parallel screening of up to 96 samples in one real-time PCR well without loss of sensitivity. As a result, up to 8,820 individual pre-amplified samples could be screened for SARS-CoV-2 within each 96-well plate of realtime PCR using the pooled testing procedure.The novel semi-nested RT-PCR assay provides a solution for highly multiplex (7-plex) detection of SARS-CoV-2 and enables 96-sample pooled detection for increase of testing capacity. .

The piezoresistive effect has been a dominant mechanical sensing principle that has been widely employed in a range of sensing applications. This transducing concept still receives great attention because of the huge demand for developing small, low-cost, and high-performance sensing devices. Many researchers have extensively explored new methods to enhance the piezoresistive effect and to make sensors more and more sensitive. Many interesting phenomena and mechanisms to enhance the sensitivity have been discovered. Numerous review papers on the piezoresistive effect have been published; however, there is no comprehensive review article that thoroughly analyses methods and approaches to enhance the piezoresistive effect. This paper comprehensively reviews and presents all the advanced enhancement methods ranging from the quantum physical effect and new materials to nanoscopic and macroscopic structures, and from conventional rigid to flexible, stretchable and wearable applications. In addition, the paper summarises results recently achieved on applying the above-mentioned innovative sensing enhancement techniques in making extremely sensitive piezoresistive transducers.

Recent advances in micro-electromechanical systems (MEMS) has allowed unprecedent perspectives for label-free detection (LFD) of biological and chemical analytes. Additionally, these LFD technologies offer the potential to design high resolution and high throughput sensing platforms, with the promise of further miniaturization. However, the immobilization of biomolecules onto inorganic surfaces without impacting their sensing abilities is crucial for designing these LFD technologies. Currently, covalent functionalization of self-assembled monolayers (SAMs) present promising pathways for improving assay sensitivity, reproducibility, surface stability and proximity of binding sites to the sensor surface. Herein, we investigate the use of chemical vapor deposition of 3-(glycidyloxypropyl)-trimethoxysilane (GOPTS) as a versatile SAM for the covalent functionalization of a SiO

Transformation of conventional 2D platforms into unusual 3D configurations provides exciting opportunities for sensors, electronics, optical devices, and biological systems. Engineering material properties or controlling and modulating stresses in thin films to pop-up 3D structures out of standard planar surfaces has been a highly active research topic over the last decade. Implementation of 3D micro and nanoarchitectures enables unprecedented functionalities including multiplexed, monolithic mechanical sensors, vertical integration of electronics components, and recording of neuron activities in 3D organoids. This paper provides an overview on stress engineering approaches to developing 3D functional microsystems. The paper systematically presents the origin of stresses generated in thin films and methods to transform a 2D design into an out-of-plane configuration. Different types of 3D micro and nanostructures, along with their applications in several areas are discussed. The paper concludes with current technical challenges and potential approaches and applications of this fast-growing research direction.

The discovery of a giant piezoresistive effect in a semiconductor heterojunction by optoelectronic coupling can open a new era for mechanical sensors. This paper develops a novel concept of opto-electronic coupling in semiconductor heterojunctions for pressure sensing. We employ non-uniform illumination of visible light on a SiC/Si heterojunction to generate a gradient of charge carriers in the SiC nanofilm. These charge carriers are then manipulated by a tuning current, producing giant relative resistance changes in the material under applied pressure. We successfully demonstrated the enhancement by opto-electronic coupling in a SiC/Si heterojunction pressure sensor of sensitivity up to 185 000 times compared to the unilluminated condition. In addition, the opto-electronic coupling enables significantly improved repeatability, stability, signal-to-noise ratio and detectable range of the pressure sensor. The ultrahigh sensitive pressure sensing mechanism by opto-electronic coupling will pave a way for development of extremely sensitive mechanical sensors.

The shear-wave velocity structures of the crust and uppermost mantle of northern Vietnam were analyzed using the receiver function (RF) method at 25 broadband stations to investigate the regional crustal structure and its tectonic evolution. In this study, we presented a new crustal shear-wave velocity structure of northern Vietnam determined through RF analysis. Our results revealed significant variations in crustal thickness and deep crustal velocities across the study area. Along the Red River shear zone (RRSZ), the patterns of the crustal structure were distinct on both sides; they were simple and complex, respectively, in the blocks on northeast and southwest. A low-velocity zone (LVZ) was widely observed in the northwestern corner of the study area, and significant lateral variations in the thickness and strength of the crustal structure were observed from north to south. This LVZ was distributed as a thick and deep zone in the north and became thinner and shallower in the central region; the LVZ finally disappeared in the south. Two end members of the origin of the LVZ were proposed. The LVZ can be considered a weak crustal layer that escaped from the southeastern margin of the Tibetan Plateau, or it may have been formed from a paleo-subducted slab beneath it because of an onsite mantle heat source. The existence of this LVZ suggests that the movement of the RRSZ is possibly concentrated above the LVZ and that extension to the upper mantle is not necessary in the present stage. The above tectonic regime supports the possibility that the RRSZ is a strikeslip fault with a feature restricted in the crust.

There is an increasing demand for measuring respiratory rate (RR) to monitor the progression of clinical events such as cardiac arrest or during the admission to the intensive care unit (ICU). Current methods of respiration monitoring are complex, invasive, expensive and therefore require alternative techniques. In this paper, we utilized wearable and flexible technology to develop humidity sensors for long-term continuous monitoring of respiration. Using manual drawing and printing techniques, the sensors were made based on graphite trace and silver nanoparticles as two different sensing materials. The surface morphologies of the devices were characterized by Scanning Electron Microscope (SEM) to show the construction of the sensors. Additionally, the material characterization was performed to obtain the Raman Spectra. Paper was chosen as a flexible substrate owing to its biodegradability, porosity, and disposability. The humidity sensing characteristics of the sensors indicated the best sensitivity of 0.0564% for Graphite on Paper (GOP) sensor. Furthermore, the hygroscopic nature of the paper enables converting the humidity changes during inhalation and exhalation into electrical signals. The electrical signals are transmitted via an interface to a computer using a simple data-logging set-up. A set of normal, deep and apnea breathing conditions could be easily differentiated from these signals along with information on respiration rate and pattern. The functionality of sensors was also tested after light and rigorous exercises. The proposed sensor combines the advantages of being low cost, non-invasive, highly sensitive, stable and holds tremendous potential for wearable/flexible healthcare technology.

Various species of selenium (Se) can be radicularly or foliarly absorbed by plants. However, differences of these species in uptake and transport via the xylem or phloem remain unclear. Maize (Zea mays L.) seedlings were grown in hydroponic solutions with five exogenous Se species [inorganic forms: selenite and selenate; and organic forms: selenomethionine (SeMet), methyl-selenocysteine (MeSeCys), and selenocystine (SeCys2)] radicularly or foliarly applied on the plants. Under radicular application, the seedlings showed higher root uptake of organic Se than inorganic forms. Moreover, the largest proportion of Se in the shoots was found under MeSeCys treatment. Se accumulation under foliar application was low. The uptake of inorganic Se was higher than that of organic forms under foliar treatments. The phloem of maize showed a strong ability for downward Se transport, although the proportion of that in the whole plant was small (

A generally accepted method to predict selenium (Se) bioavailability of long-term contaminated soils has not yet been established, even if risk assessments in selenosis areas are crucial. In this study, a set of methods were tested to assess the bioavailability of Se to field maize. Fifty maize (Zea mays L.) samples and corresponding soils were collected from a selenosis area (Ziyang, China). The diffusive gradients in thin-films (DGT) technique and the traditional chemical extraction methods, including seven single-step extraction procedures and a five-step sequential extraction were used to predict the bioaccumulation of Se in plant. The result verified the presence of 50% of total Se in the form of residual Se fraction, followed by organic-bound and Fe-Mn oxide-bound Se fractions in soil. In addition, Se6+, Se4+, and Se2− were all detected in the solution extracted by H2O, KCl, phosphate-buffered solution (PBS), NaHCO3, ethylenediaminetetraacetic acid-2Na (EDTA-2Na) and ammonium bicarbonate–diethylenetriaminepentaacetic acid (AB-DTPA), but Se6+ was not extracted by NaOH. The Se extracted by single-step extraction methods was weakly correlated with the Se uptake by plants with relatively high Se concentration (>3 mg·kg−1). The abilities of the tested methods to predict Se bioavailability in naturally Se-enriched soils declined in the following order: DGT > soil solution > PBS > KCl > H2O > NaHCO3 > EDTA > DTPA > NaOH. The ratio of CDGT to soil solution Se (Csoln) totaled 0.13, indicating an extremely low Se supply from the soil solid phase to the soil solution. Se measured by DGT was mainly derived from the soluble and exchangeable Se fractions that can accurately reflect the plant-absorbed Se pool. Therefore, the DGT technique is highly applicable in the simultaneous prediction of Se bioavailability in naturally Se-enriched soils.

Single-crystalline silicon carbide (3C-SiC) on the Si substrate has drawn significant attention in recent years due to its low wafer cost and excellent mechanical, chemical, and optoelectronic properties. However, the applications of the structure have primarily been focused on piezoresistive and pressure sensors, bio-microelectromechanical system, and photonics. Herein, we report another promising application of the heterostructure as a laser spot position-sensitive detector (PSD) based on the lateral photovoltaic effect (LPE) under nonuniform optical illuminations at zero-bias conditions. The LPE shows a linear dependence on spot positions, and the sensitivity is found to be as high as 33 mV/mm under an illumination of 2.8 W/cm2 (635 nm). The structure also exhibits a linear dependence of the LPE over a large distance (7 mm) between two electrodes, which is crucial for PSDs as the region with a linear dependence of LPE is only usable for PSDs. The LPE at different spot positions and under different illumination conditions have been investigated and explained based on the energy-band analysis. The temperature dependence of the LPE and position sensitivity is also investigated. Furthermore, the two-dimensional mapping of the lateral photovoltages reveals the potential for utilizing the 3C-SiC/Si heterostructure to detect the laser spot position precisely on a plane.

Mine and smelter soil contaminations with Pb, Cu, Cd, and Zn have become serious problems in China, because of anthropogenic activities. Little is known about the efficacy of residual lime (RL) single and integrated with residual Ca-bentonite (RCB), residual tobacco biochar (RTB), and residual zeolite (RZ) on the stability of toxic metals and reduces their uptake by corn after harvesting of Chinese cabbage. A previous pot trial investigated L single and integrated with CB, TB, and Z on the stabilization and absorption of Pb, Cd, Cu, and Zn using Chinese cabbage, and corn was later selected as the test plant in the present work and grown in mine-contaminated (M-C), smelter heavily, and low contaminated (S-HC and S-LC) soils. Diethylenetriamine pentaacetic acid (DTPA)–extractable method was used to examine the bioavailability of Pb, Cd, Cu, and Zn in M-C, S-HC, and S-LC soils, through atomic adsorption spectrophotometer. The results indicated that the maximum immobilization of Pb reached 63.9% with RL + RZ, Cd 61.7% with RL + RTB, Cu 94.2% with RL + RZ, and Zn 62.4% with RL + RTB, but RL + RTB and RL + RZ treatments mobilized Pb up to 22.44 and 19.9% and RL + RCB mobilized the Cu nearly 53.1% than control. The residual impact of amendments did not support to corn dry biomass and height. The Pb absorption in the corn shoot was significantly reduced by 35.4% with RL + RZ, Cd 65.2% with RL + RTB, Cu 25.2% RL + RCB, and Zn 44.2% with RL + RZ. The accumulation of Pb in the corn root was significantly reduced by 52.1% with RL + RTB, Cd 38.6% with RL + RZ, Cu 51.01% with RL + RZ, and Zn 62.7% with RL + RZ rather than control. Our results demonstrate that the RL alone and combined with RTB, RCB, and RZ could be a feasible approach for successful remediation of Cd and Zn in mine-contaminated soil and Pb, Cd, Cd, and Zn in smelter-contaminated soils. Overall, the long-term residual impact of amendments for the restoration of mine-/smelter-contaminated soils should be verified under field scale.

Although direct ink writing (DIW) is a versatile 3D printing technique, progress in DIW has been constrained by the stringent rheological requirements for printable conductive nanocomposites, particularly at smaller length scales. In this work, we overcome these challenges using an aqueous nanocomposite ink with polydimethylsiloxane (PDMS) submicrobeads and an electrochemically derived graphene oxide (EGO) nanofiller. This nanocomposite ink possesses a thixotropic, self-supporting viscoelasticity. It can be easily extruded through very small nozzle openings (as small as 50 μm) allowing for the highest resolution PDMS DIW reported to date. With a mild thermal annealing, the DIW-printed device exhibits low resistivity (1660 Ω·cm) at a low percolation threshold of EGO (0.83 vol.%) owing to the unique nanocomposite structure of graphene-wrapped elastomeric beads. The nanocomposite ink was used to print wearable, macro-scale strain sensing patches, as well as remarkably small, micron-scale pressure sensors. The large-scale strain sensors have excellent performance over a large working range (up to 40% strain), with high gauge factor (20.3) and fast responsivity (83 ms), while the micron-scale pressure sensors demonstrated high pressure sensitivity (0.31 kPa−1) and operating range (0.248–500 kPa). Ultrahigh resolution, multi-material layer-by-layer deposition allows the engineering of microscale features into the devices, features which can be used to tune the piezoresistive mechanism and degree of piezoresistivity.

This work reports the strain dependence of the offset voltage in an AlGaN/GaN van der Pauw device under mechanical strain. The AlGaN/GaN heterostructure was grown on a sapphire (0 0 0 1) wafer by using a metal organic chemical vapor deposition (MOCVD) process. Taking advantage of the four-terminal configuration, the fabricated van der Pauw device exhibited an excellent repeatability and linearity with a significant change of the offset voltage under application of tensile and compressive strains. In particular, the sensitivity of the device to the applied strain was found to be as large as 3 ( μ V/V)/ppm, indicating the feasibility of using this effect for mechanical sensing applications. The sensing mechanism of the device is explained via the alteration of the sheet carrier concentration at the AlGaN/GaN interface and the asymmetric current flux in the 2DEG van der Pauw device.

Self-powered photodetectors (PDs) are highly desirable for many applications, ranging from smart cities to optical communications. Herein, we report on a self-powered broadband [UV to near-infrared (NIR)] PD based on a single-crystalline SiC (100)/Si (100) heterojunction. In self-powered photovoltaic detection mode, the detector exhibits a high responsivity (2500 V/W at $\text {8.0} \times \text {10}^{\text {-6}}$ W/cm2, 521 nm) and specific detectivity (~1013 Jones at $8.0 \times 10^{-6}$ W/cm2, 521 nm) under UV, visible, and NIR spectral illuminations thanks to the superior rectification property of the heterojunction which results in significantly reducing the dark current. The device also shows high illumination ON/ OFF switching ratios, as high as $\text {2.2} \times \text {10}{^{\text {7}}}$ , with an excellent stability and repeatability. A detailed insight about electron–hole pairs generation, separation, and Fermi-energy level shifting at different illumination conditions has been elucidated via energy band diagrams.

Silicon carbide (SiC) has been extensively investigated in the last decade, specifically for applications in harsh environments. However, most SiC sensors require an external power supply, which cannot operate at high temperatures. This letter develops a new sensing technology in a SiC platform based on near field communication to eliminate the requirement for wired power sources. The 3C-SiC temperature sensors were fabricated from a SiC-on-insulator substrate formed by anodic bonding. The sensors functioned based on the thermoresistance of the SiC films with the high TCR of −13 000 ppm/K at 300 K and −3 000 ppm/K at 600 K. The resistance change of the sensors was wirelessly measured using a reading coil placed outside of the heating chamber, showing a significant resonant-frequency-shift (−400 ppm/K at 600 K) of the coupling impedance under temperature variation. The proposed technique is promising for the development of wireless wide-band-gap sensors used in extreme conditions.

The development of a multimodal sensing platform with multiple layers for electronic skin (e-skin) sensing of temperature and pressure has attracted considerable interest to practical applications in soft robotics, human-machine interfaces, and wearable health monitoring. In this work, we demonstrated a new platform technology with multiple sandwiched layers of highly oriented carbon nanotube membrane and polyacrylonitrile for the integration of pressure and temperature sensory functionalities into a single platform that is thin, ultra-lightweight, flexible, and wearable. The key technology of in situ deposition of sensor platform on objects or in robot interface makes this a unique method for the development of e-skins for robotic applications, offering a new approach to wearable electronics and portable health care.