Nature-Inspired Gelatin-Based Adhesive Hydrogel: A Rapid and User-Friendly Solution for Hemostatic Applications.

Conventional hemostatic agents face challenges in achieving rapid hemostasis and effective tissue repair due to limited hemostatic scenarios, suboptimal efficacy, and inadequate adhesion to wet tissues. Drawing inspiration from nature-sourced materials, a gelatin-based adhesive hydrogel (AOT)  is designed, easily prepared and quick to form, driven by Schiff base and multiple hydrogen bonds for applications in arterial and liver bleeding models. AOT exhibits exceptional adhesion to wet tissues (48.67 ± 0.16 kPa) and displays superior hemostatic properties with reduced blood loss and hemostatic time compared to other hydrogels and conventional hemostatic materials. Moreover, AOT exhibits good biocompatibility and biodegradability. In summary, this easily prepared adhesive hydrogel has the potential to supplant traditional hemostatic agents, offering a novel approach to achieve swift sealing of hemostasis and facilitate wound healing and repair in broader application scenarios, owing to its unique advantages.

Hierarchical Wrinkles with Piezopotential Enhanced Surface Tribopolarity for High-Performance Self-Powered Pressure Sensor.

Achieving both high sensitivity and wide detecting range is significant for the applications of triboelectric nanogenerator-based self-powered pressure sensors (TPSs). However, most of the previous designs with high sensitivity usually struggle in a narrow pressure detection range (<30 kPa) while expanding the detection range normally sacrifices the sensitivity. To overcome this well-known obstacle, herein, piezopotential enhanced triboelectric effect realized by a rationally designed PDMS/ZnO NWs hierarchical wrinkle structure was exploited to develop a TPS (PETPS) with both high sensitivity and wide detecting range. In this PETPS design, the piezopotential derived from the deformation of ZnO NWs enhances its tribo-charge transferring ability; meanwhile, the hierarchical structure helps to establish a dynamically self-adjustable contact area. Benefiting from these advantages, the PETPS simultaneously achieves high sensitivity (0.26 nC cm-2 kPa-1 from 1 to 25 kPa, and 0.02 nC cm-2 kPa-1 from 25 to 476 kPa), fast response (46 ms), wide sensing range (1 to 476 kPa), and good stability (over 4000 cycles). In addition, the output charge density that is independent of the speed rate of driven force was adopted as the sensing signal of PETPS to replace the commonly used peak voltage/current values, enabling it more adaptive to accurately detect pressure variation in real applications.

Fully integrated on-chip FBG interrogator for high-accuracy measurement of wavelengths.

We present the design and fabrication of an on-chip FBG interrogator based on arrayed waveguide grating (AWG) technology. The spectral overlap between adjacent channels in the integrated AWG is significantly enhanced through a combination approach involving the reduction of the output waveguide spacing and an increase in the input waveguide width. As a result of these design choices, our AWG demonstrates excellent spectral consistency, with spectral cross talk exceeding 30 dB. The interrogator seamlessly combining optical and circuitry components achieves full integration and enables a wide range of interrogation wavelengths, including C-band and L-band. With an interrogation range extending up to 80 nm, it theoretically has the capacity to simultaneously interrogate the wavelengths of 20 FBG sensors. Experimental findings demonstrate an absolute interrogation accuracy of less than 2 pm for the fully integrated interrogator. With its compact size, cost-effectiveness, exceptional precision, and ease of integration, the proposed interrogator holds a substantial promise for widespread application in the realm of FBG sensing.

Enhancing the Performance of a Self-Standing Si/PCNF Anode by Optimizing the Porous Structure.

Embedding silicon nanoparticles into carbon nanofibers is one of the effective methods to fabricate a self-standing and binder-free Si-based anode material for lithium-ion batteries. However, the sluggish Li-ion transport limits the electrochemical performance in the regular strategies, especially under high rate conditions. Herein, a kind of silicon nanoparticle in porous carbon nanofiber structures (Si/PCNFs) has been fabricated through a facile electrospinning and subsequent thermal treatment. By adjusting the mass ratio to 0.4:1, a Si/PCNF anode material with an effective Li+-migration pathway and excellent structural stability can be obtained, resulting in an optimal electrochemical performance. Although increasing the mass ratio of PEG to PAN further can lead to a larger pore size and can be beneficial to Li+ migration, thus being profitable for the rate capacity, the structural stability will get worse at the same time as more defects will form and lead to a weaker C-C binding, thus decrease the cycling stability. Remarkably, the rate capacity reaches 1033.4 mA h g-1 at the current density of 5 A g-1, and the cycling capacity is 933.2 mA h g-1 at 0.5 A g-1 after 200 cycles, maintaining a retention rate of 80.9% with an initial coulombic efficiency of 83.37%.

Adjustment of oxygen vacancy states in ZnO and its application in ppb-level NO2 gas sensor.

Oxygen vacancy (VO) is long believed as a key factor influencing the gas sensing properties. However, the concentration of VO is generally focused while the VO state is neglected, which masks the inherent mechanism of gas sensor. Using a post annealing process, the influence of VO states on the response of ZnO nanofilm to NO2 gas is investigated in this study. The systematical analysis of the results obtained by different methods indicates a transformation of VO from the neutral to the doubly ionized state during post annealing treatment. The results also imply that the gas sensing properties is not directly correlated with the VO concentration. And due to the competitive adsorption of ambient O2, the neutral VO is majorly occupied by the adsorbed O2 while the VO in doubly ionized state can promote the adsorption of NO2. Consequently, the transition of VO from the neutral to the doubly ionized state can lead to a dramatic increase of the response to NO2, from 733 to 3.34 × 104 for 100 ppm NO2. Guided by this mechanism, NO2 gas sensing in ppb-level is also achieved: the response reaches 165% to 25 ppb (0.025 ppm) NO2 with a good repeatability.

Ultrasensitive Fiber-Based ZnO Nanowire Network Ultraviolet Photodetector Enabled by the Synergism between Interface and Surface Gating Effects.

A flexible UV photodetector with a high on/off ratio is extremely important for environmental sensing, optical communication, and flexible optoelectronic devices. In this work, a flexible fiber-based UV photodetector with an ultrahigh on/off ratio is developed by utilizing the synergism between interface and surface gating effects on a ZnO nanowire network structure. The synergism between two gating effects is realized by the interplay between surface band bending and the Fermi level through the nanowire network structure, which is proved through the control experiments between the ZnO micro/nanowire photodetector and micro/nanowire junction photodetector, and the corresponding Kelvin probe force microscopy (KPFM) measurements. The on/off ratio of the fiber-based ZnO nanowire network UV photodetector reaches 1.98 × 108 when illuminated by 1.0 mW cm-2 UV light, which is 20 times larger than the largest reported result under the same UV illumination. This new UV sensor also has a high resolution to UV light intensity change in the nW cm-2 range. Furthermore, when the fiber-based photodetector is curved, it still shows excellent performance as above. This work gives a new effective route for the development of a high-performance UV photodetector or other optoelectronic detection devices.

Flexible Self-Powered ZnO Film UV Sensor with a High Response.

Response (on/off ratio) is one of the key parameters of ultraviolet (UV) sensors. In this paper, a kind of highly sensitive ZnO UV sensor with highly increased on/off current ratio was designed and developed. Under a weak UV intensity of 0.1 mW/cm2, this ultrathin ZnO film-based UV sensor has an on/off current ratio of 1.3 × 106 which is 3 times higher than the record value for ZnO-based UV sensors. In addition, it shows good flexibility and stable UV detection property during the bending process. When bending the sensor to a radius of curvature of about 18.5 mm, the sensor also shows high UV detection performance.

Mechanism of Sensitivity Enhancement of a ZnO Nanofilm Gas Sensor by UV Light Illumination.

Although ultraviolet (UV) light illumination has been widely used to increase the sensitivity of semiconductor gas sensors, its underlying mechanism is still blurred and controversial. In this work, the influence of UV light illumination on the sensitivity of ZnO nanofilm gas sensors is explored experimentally and simulated based on a modified Wolkenstein's model. The influential factors on sensitivity are determined respectively: the surface band bending and Fermi level are measured by Kelvin probe force microscopy, the binding energy and extrinsic surface state are calculated by density functional theory, and the depletion of the whole semiconductor caused by the finite size is illustrated by the transfer characteristics of a field effect transistor. With all these factors taken into consideration, the surface state densities of adsorbed O2 and NO2 molecules in the dark and under UV light illumination are calculated which determine the sensitivity. Good agreement has been obtained between the experiment and simulation results. Accordingly, when NO2 is introduced into the atmosphere, the enhancement of sensitivity is ascribed to the more dramatic increase of surface state density and surface band bending activated by the UV light illumination compared with that in the dark. This finding is critical and would contribute greatly to the development of gas sensors with high sensitivity.

Clarifying the high on/off ratio mechanism of nanowire UV photodetector by characterizing surface barrier height.

The response of semiconductor nanowire UV sensors represented by ZnO nanowire UV sensor is usually explained by the adsorption and desorption of oxygen molecules, but with the great increase of these sensors' on/off ratio in recent years, this explanation is inadequate and the inner mechanism for the large on/off ratio urgently needs to be explored. Here, the distribution of carrier concentration in a ZnO nanowire is found to be determined as a function of the radius of the nanowire, using a calibrated surface photovoltage method and space charge model. A critical radius is indicated which determines the carrier concentration and photoresponse behavior of the nanowire. When the radius is below this critical value, the carrier concentration in the dark decreases dramatically compared with that of the nanowire under UV light illumination. Specifically, a decrease of carrier concentration by 4-5 orders of magnitude occurs when the radius is below 50 nm, which causes the on/off ratio to vary by the same orders of magnitude. When the radius is above the critical value, the influence of radius on carrier concentration is nonsignificant and the on/off ratio is below 100. Finally, we found that the high on/off ratio of the ZnO nanowire should be ascribed to the complete depletion of the nanowire led by the interplay of radius and surface band bending rather than the change in width of the depletion layer as most papers have suggested.

Magnetic force driven nanogenerators as a noncontact energy harvester and sensor.

Nanogenerator has been a very important energy harvesting technology through directly deforming piezoelectric material. Here, we report a new magnetic force driven contactless nanogenerator (CLNG), which avoids the direct contact between nanogenerator and mechanical movement source. The CLNG can harvest the mechanical movement energy in a noncontact mode to generate electricity. Their output voltage and current can be as large as 3.2 V and 50 nA, respectively, which is large enough to power up a liquid crystal display. We also demonstrate a means by which a magnetic sensor can be built.