A new β-amylase detection strategy based on encapsulated enzyme in magnetic layered double hydroxide with high sensitivity and simplified workflow.

EPSRC Centre for Innovative Manufacturing in Food

Flexible tactile sensors with high sensitivity typically suffer from a dramatically reduces pressure resolution with increasing pressure, resulting in narrow linear ranges and limited application scenarios. Herein, a capacitive tactile sensor based on cone‐shaped electrodes (CSE) that can maintain high sensitivity over a broad linearity range is proposed. The linear response comes from the novel sensing mechanism based on the change in the facing electrode area and the rational design of the conical architecture. Finite element analysis (FEA) confirms that the interfacial contact area between the elastic electrodes and the dielectric layer can respond linearly to pressure over a broad spectrum. Based on this strategy, the fabricated sensors perform a high sensitivity (0.23 kPa−1) and superior linearity (R2 = 0.999) across a wide pressure range of up to 130 kPa. The sensors demonstrate several key features, such as good repeatability, fast response speed, low detection limit, and high durability. These attributes enable the successful use of the sensors for monitoring artery pulses and providing weighting capabilities to robots, showing promising potential for applications in daily health monitoring and human‐machine interaction.

Hydrogen sulfide (H2S) is an important respiratory biomarker of many diseases, and thus, developing H2S gas sensors with low detection limits at low operating temperatures is essential for the early diagnosis of diseases in low-resource environments. Although lead halide perovskites have unique electronic and optical properties, the high toxicity of lead has prompted the development of alternative materials. In this study, Cs2AgBiCl6 was synthesized using a simple method. The sensor based on Cs2AgBiCl6 showed excellent sensing of H2S gas at room temperature over a wide humidity range, with high response (90.6 vs 10 ppm of H2S) and fast response speed (99.6 s vs 400 ppb H2S). The detection limit was low (5 ppb H2S), and the selectivity at room temperature was excellent. Small changes in H2S concentration (<100 ppb) were detected as a fully reversible resistance signal. Additionally, sum frequency vibration spectroscopy and DFT calculations showed that the high gas sensitivity was attributed to the physical adsorption of H2S at Cl vacancies on the surface of Cs2AgBiCl6, as well as efficient charge transfer. This work provides an avenue for developing high-performance gas sensors based on nontoxic, wide band gap, halide double perovskite semiconductors operating at room temperature.

Chitosan stabilized copper iodide nanoparticles enabled nano-bio-engineered platform for efficient electrochemical biosensing of dopamine

WARNING : The light-emitting molecular structures responsible for the chemiluminescence and fluorescence phenomena are not necessarily the same!

Highly sensitive microfiber strain sensors are promising for the detection of mechanical deformations in applications where limited space is available. In particular for in situ battery thickness monitoring where high resolution and low detection limit are key requirements. Herein, the realization of a highly sensitive strain sensor for in situ lithium-ion (Li-ion) battery thickness monitoring is presented. The compliant fiber-shaped sensor is fabricated by an upscalable wet-spinning method employing a composite of microspherical core-shell conductive particles embedded in an elastomer. The electrical resistance of the sensor changes under applied strain, exhibiting a high strain sensitivity and extremely low strain detection limit of 0.00005 with high durability of 10 000 cycles. To demonstrate the accuracy and ease of applicability of this sensor, the real-time thickness change of a Li-ion battery pouch cell is monitored during the charge and discharge cycles. This work introduces a promising approach with the least material complexity for soft microfiber strain gauges.

Flexible capacitive pressure sensors with simple structure and low power consumption have attracted great interest because of their promising applications in wearable electronics. However, assembling a pressure sensor with high sensitivity, low detection limit, and wide dynamic range is still a big challenge. Here, a sandwich‐like, flexible capacitive pressure sensor is reported with micropyramid array electrode and porous dielectric layer. Under external stimulus pressure, the distance between two electrodes, and dielectric constant of dielectric layer will change simultaneously, resulting in high sensitivity (2.51 kPa−1) of the sensor. Due to the micropyramid array electrode, the sensor exhibits low detection limit (2.0 Pa), fast response speed (84 ms), wide working range (&gt;10 kPa), and high stability (&gt;5000 dynamic cycles). Finite‐element analysis also reveals that the larger duty ratio and altitude of micropyramid arrays lead to higher sensor sensitivity. By depicting the deformation of micropyramid during compression, the sensing mechanism of these sensors is discovered, providing a potential direction for developing sensitivity and linear range. Additionally, the sensor has been demonstrated to be efficient in monitoring human motion, such as muscle activation and rope skipping, showing high potential in the field of sport wearable equipment.

Flexible pressure sensors have aroused tremendous attention, owing to their broad applications in healthcare, robotics, and prosthetics. So far, it remains a critical challenge to develop low-cost and controllable microstructures for flexible pressure sensors. Herein, a high-sensitivity and low-cost flexible piezoresistive sensor was developed by combining a controllable graphene-nanowalls (GNWs) wrinkle and a polydimethylsiloxane (PDMS) elastomer. For the GNWs-PDMS bilayer, the vertically grown GNWs film can effectively improve the interface strength and form delamination-free conformal wrinkles. More importantly, a controllable microstructure can be easily tuned through the thermal wrinkling method. The wrinkled graphene-nanowalls (WG) piezoresistive sensor has a high sensitivity (S = 59.0 kPa-1 for the 0-2 kPa region and S = 4.8 kPa-1 for the 2-20 kPa region), a fast response speed (<6.9 ms), and a low limit of detection (LOD) of 2 mg (∼0.2 Pa). The finite element method was used to analyze the working mechanism of the sensor, which revealed that the periods of the wrinkles play a dominant role in the performances of the sensors. These prominent merits enable wrinkled graphene sensors to successfully detect various signals from a weak stimulus to large pressures, for example, the detection of weak gas and plantar pressure. Furthermore, object manipulation, tactile imaging, and braille recognition applications have been demonstrated, showing their great potential in prosthetics limbs and intelligent robotics.

MicroRNAs (miRNAs) have been recently regarded as clinically important biomarkers for early cancer diagnostic. Accumulative evidences have proved that dysregulated expression of miRNAs is closely related with the occurrence, diagnosis and treatment of cancer [1]. Conventional methods of miRNA detection have some limitations like requiring large amount of sample input, expensive instrumentation, and long analysis time. To address these shortcomings as well as providing multiplexing capability, selectivity, and real-time measurement different types of cancer biosensors have been developed. Among them electrochemical biosensors have shown great promise for this application due to their high sensitivity, specificity, cost-effectiveness, and compatibility with the miniaturization [2]. A label-free and ultrasensitive impedimetric biosensor for miRNA detection is reported in this study. We utilized a glassy carbon electrode (GCE) modified with multi-wall carbon nanotube (MWCNT) as a biosensor platform. Incorporation of nanomaterials such as MWCNT offers unique advantages including enhanced electronic properties, higher surface area, and rapid electrode kinetics which leads to higher sensitivities and lower limit of detection [3]. Capture DNA probes were immobilized onto the surface of MWCNT modified electrode using a novel molecular tethering agent. All surface modification, immobilization, and hybridization between probe DNA and the target miRNA were investigated by electrochemical analyses. Besides, different variables such as probe concentration, pH, ionic strength, and hybridization time were investigated and optimized to get the optimal experimental conditions for miRNA detection. The obtained results demonstrated that the proposed biosensor exhibits excellent analytical properties including high sensitivity, low detection limit, selectivity, and reproducibility for miRNA detection. References Lan H, Lu H, Wang X, Jin H (2015) MicroRNAs as potential biomarkers in cancer: opportunities and challenges. BioMed research international 2015Kilic T, Erdem A, Ozsoz M, Carrara S (2018) MicroRNA biosensors: Opportunities and challenges among conventional and commercially available techniques. Biosensors and Bioelectronics 99:525-546Oliveira T, Morais S (2018) New Generation of Electrochemical Sensors Based on Multi-Walled Carbon Nanotubes. Applied Sciences 8 (10):1925 Figure 1

Digitalising food manufacturing

The “ozone hole” and ozone pollution have caused numerous environmental problems that threaten human survival. Therefore, real-time monitoring of the concentration of trace ozone components in the atmosphere is critical. In recent decades, the ethylene chemiluminescence method has become a common method for diagnosing trace ozone in the air due to its high sensitivity, low detection limit, and simple operation. However, this method requires a large amount of high-purity ethylene, which presents risks such as flammability and explosion during actual measurements. Therefore, this paper proposes a new strategy for measuring trace ozone levels at the ppb with high safety and sensitivity, based on the chemiluminescence reaction mechanism between NO and ozone. Firstly, this article designs a system for preparing quantitative ozone standard gas using the principle of plasma discharge and the ultraviolet broadband absorption concentration measurement method; Subsequently, a fluorescence measurement system with high sensitivity and low detection limit was built based on the principle of chemiluminescence and weak light detection technology; Finally, experimental investigations on the chemiluminescence laws of traditional hydrocarbons and NO chemiluminescence laws was conducted with the help of the aforementioned weak light measurement system. The results indicate that the NO chemiluminescence reaction is more prominent than hydrocarbons and is an ideal excitation gas for ozone fluorescence detection. The chemiluminescence signal of NO is approximately 17 times higher than that of C2H4, 68 times higher than that of C2H2, and much higher than that of other hydrocarbons such as CH4, C2H6. The experiment also showed that within the concentration range of 0-10 ppm and103 ppm of NO excitation gas, the measurement system has high linearity and sensitivity, drastically improving the safety and sensitivity of the measurement system. For example, when the NO concentration is 1000 ppm, the correlation linearity coefficient R2 is above 0.999, the lower limit of Allan variance detection can reach approximately 20 ppt.

To optimize the technical conditions for simultaneous detection of serum ferritin(SF), soluble transferrin receptor(sTfR), C-reactive protein(CRP)and retinol-binding protein four(RBP4)by liquid protein microarray. The trapping antibodies of the four proteins were coupled to magnetic beads with different codes, and the samples were added to the 96-well plate. The antibodies were detected by double antibody sandwich method. The serum of 5 patients were diluted with commercial diluent, 1% albumin from bovine serum(BSA) and phosphate buffer saline(PBS) to detect 4 target proteins, and the results were compared. The antibody specific binding ability was tested by antibody specific validation test. The interference between proteins was verified by the paired t test of the signal values of the single reaction system and the mixed reaction system. The lower limit of detection and the limit of biological detection of each protein were found by using multiple dilution method. The standard curve and regression equation were established. 1%BSA and PBS were selected to replace commercial diluent as diluents for the detection of 4 proteins in this experiment. The cross-reaction rate of the four antigens with other capture antibodies and detection antibodies was less than 2%. There was no significant difference in the signal value of each protein in the single reaction system and the mixed reaction system. The limit of detection and the limit of biological detection of SF were 1.155 and 1.625 ng/mL, respectively. The lower limit of detection and the limit of biological detection of sTfR were 2.682 and 5.208 ng/mL, respectively. The detection limit and biological detection limit of CRP were 0.302 and 0.391 ng/mL, respectively. The lower limit of detection and the limit of biological detection for RBP4 were 1.814 and 3.540 ng/mL, respectively. The standard curve and regression equation of the four proteins within the common linear range were as follows: SF y=172.5x-39.65, R~2=0.9968;sTfR y=60.10x+77.38, R~2=0.9972;CRP y=-6.000x~2+210.3x+246.1, R~2=0.9063;RBP4 y=-0.6998x~2+64.31x+134.8, R~2=0.9748. The conditions of the detection platform for four proteins such as SF, sTfR, CRP and RBP4 were optimized by using liquid protein chip technology.

Flexible electronic sensors composed of flexible film and conductive materials play an increasingly important role in wearable and internet information transmission. It has received more and more attention and made some progress over the decades. However, it is still a great challenge to prepare biocompatible and highly transparent conductive films. Egg white is a pure natural protein‐rich material. Hydroxypropylmethyl cellulose has a good compatibility and high transparency, which is an ideal material for flexible sensors. Here, we overcome the problem of poor mechanical flexibility and electrical conductivity of protein, and develop a high transparency and good flexibility hydroxypropylmethyl cellulose/egg white protein composite membrane‐based triboelectric nanogenerator (‘X’‐TENG). The experimental results show that the flexible pressure sensor based on ‘X’‐TENG has a high sensitivity, fast response speed, and low detection limit. It can even be used as a touch/pressure sensing artificial electronic skin. It can also be made into an intelligent waffle keyboard for recording and tracking users of the keyboard. Our strategy may provide a new way to easily build flexible electronic sensors and move toward practical applications.

A highly-sensitive wearable capacitance pressure sensor based on calcium copper titanate/polydimethysiloxane/graphene oxide and polydimethysiloxane/silver nanowires sanwich strustures combination for human body monitoring

Gossypol (Gsp) and antibiotics present in water bodies become organic pollutants that are harmful to human health and the ecological environment. Accurate and effective detection of these pollutants has far-reaching significance in many fields. A new three-dimensional metal-organic framework (MOF), {[Eu3(L)2(HCOO-)(H2O)3]·2H2O·2DMF}n (Eu-MOF), was synthesized from 3,5-bis(2,4-dicarboxylphenyl)nitrobenzene (H4L) ligand and Eu3+ via the solvothermal method in this paper. The Eu-MOF demonstrates strong red fluorescence and can remain stable in different pH solutions. The MOF fluorescence probe could detect organic pollutants through the "shut-off" effect, with a fast response speed and a low detection limit [Gsp, nitrofurantoin (NFT), and nitrofurazone (NFZ) for 0.43, 0.38, and 0.41 μM, respectively]. During the testing process, Eu-MOF exhibited good selectivity and recoverability. Furthermore, the mechanism of fluorescence quenching was investigated, and the recoveries were also good in real samples. This paper introduced a deep learning model to recognize the fluorescence images, a portable intelligent logic detector designed for real-time detection of Gsp by logic gate strategy, and an anticounterfeiting mark prepared based on inkjet printing. Importantly, this work provides a new way of thinking for the detection of organic pollutants in water with high sensitivity and practicality by combining the fluorescence probe with machine learning and logical judgment.