查看更多>>摘要：Flexible pressure sensors are lightweight and highly sensitive,making them suitable for use in small portable devices to achieve precise measurements of tiny forces.This article introduces a low-cost and easy-fabrication strategy for piezoresistive flexible pressure sensors.By embedding silver nanowires into a polydimethylsiloxane layer with micro-pyramids on its surface,a flexible pressure sensor is created that can detect low pressure(17.3 Pa)with fast response(＜20 ms)and high sensitivity(69.6 mA kPa-1).Furthermore,the pressure sensor exhibits a sensitive and stable response to a small amount of water flowing on its surface.On this basis,the flexible pressure sensor is innovatively combined with a micro-rotor to fabricate a novel urinary flow-rate meter(uroflowmeter),and results from a simulated human urination experiment show that the uroflowmeter accurately captured all the essential shape characteristics that were present in the pump-simulated urination curves.Looking ahead,this research provides a new reference for using flexible pressure sensors in urinary flow-rate monitoring.
查看更多>>摘要：Sensitive detection and precise quantitation of trace-level crucial biomarkers in a complex sample matrix has become an important area of research.For example,the detection of high-sensitivity cardiac troponin Ⅰ(hs-cTnⅠ)is strongly recommended in clinical guidelines for early diagnosis of acute myocardial infarction.Based on the use of an electrode modified by single-walled carbon nanotubes(SWCNTs)and a Ru(bpy)32+-doped silica nanoparticle(Ru@SiO2)/tripropylamine(TPA)system,a novel type of electrochemiluminescent(ECL)magneto-immunosensor is developed for ultrasensitive detection of hs-cTnⅠ.In this approach,a large amount of[Ru(bpy)3]2+is loaded in SiO2(silica nanoparticles)as luminophores with high luminescent efficiency and SWCNTs as electrode surface modification material with excellent elec-trooxidation ability for TPA.Subsequently,a hierarchical micropillar array of microstructures is fabricated with a magnet placed at each end to efficiently confine a single layer of immunomagnetic microbeads on the surface of the electrode and enable 7.5-fold signal enhancement.In particular,the use of transparent SWCNTs to modify a transparent ITO electrode provides a two-order-of-magnitude ECL signal amplifi-cation.A good linear calibration curve is developed for hs-cTnⅠ concentrations over a wide range from 10 fg/ml to 10 ng/ml,with the limit of detection calculated as 8.720 fg/ml(S/N=3).This ultrasensitive immunosensor exhibits superior detection performance with remarkable sta-bility,reproducibility,and selectivity.Satisfactory recoveries are obtained in the detection of hs-cTnⅠ in human serum,providing a potential analysis protocol for clinical applications.
查看更多>>摘要：The development of tissue engineering and regeneration research has created new platforms for bone transplantation.However,the prepara-tion of scaffolds with good fiber integrity is challenging,because scaffolds prepared by traditional printing methods are prone to fiber cracking during solvent evaporation.Human skin has an excellent natural heat-management system,which helps to maintain a constant body tem-perature through perspiration or blood-vessel constriction.In this work,an electrohydrodynamic-jet 3D-printing method inspired by the thermal-management system of skin was developed.In this system,the evaporation of solvent in the printed fibers can be adjusted using the temperature-change rate of the substrate to prepare 3D structures with good structural integrity.To investigate the solvent evaporation and the interlayer bonding of the fibers,finite-element analysis simulations of a three-layer microscale structure were carried out.The results show that the solvent-evaporation path is from bottom to top,and the strain in the printed structure becomes smaller with a smaller temperature-change rate.Experimental results verified the accuracy of these simulation results,and a variety of complex 3D structures with high aspect ratios were printed.Microscale cracks were reduced to the nanoscale by adjusting the temperature-change rate from 2.5 to 0.5 ℃ s-1.Opti-mized process parameters were selected to prepare a tissue engineering scaffold with high integrity.It was confirmed that this printed scaffold had good biocompatibility and could be used for bone-tissue regeneration.This simple and flexible 3D-printing method can also help with the preparation of a wide range of micro-and nanostructured sensors and actuators.
查看更多>>摘要：Flexible sensors are used widely in wearable devices,specifically flexible piezoresistive sensors,which are common and easy to manipulate.However,fabricating such sensors is expensive and complex,so proposed here is a simple fabrication approach involving a sensor containing microstructures replicated from a sandpaper template onto which polydimethylsiloxane containing a mixture of graphene and carbon nan-otubes is spin coated.The surface morphologies of three versions of the sensor made using different grades of sandpaper are observed,and the corresponding pressure sensitivities and linearity and hysteresis characteristics are assessed and analyzed.The results show that the sensor made using 80-mesh sandpaper has the best sensing performance.Its sensitivity is 0.341 kPa-1 in the loading range of 0-1.6 kPa,it responds to small external loading of 100 Pa with a resistance change of 10％,its loading and unloading response times are 0.126 and 0.2 s,respectively,and its hysteresis characteristic is～7％,indicating that the sensor has high sensitivity,fast response,and good stability.Thus,the presented piezoresistive sensor is promising for practical applications in flexible wearable electronics.
查看更多>>摘要：Ceramic matrix composites(CMCs)are highly promising materials for the next generation of aero-engines.However,machining of CMCs suffers from low efficiency and poor surface finish,which presents an obstacle to their wider application.To overcome these problems,this study investigates high-efficiency deep grinding of CMCs,focusing on the effects of grinding depth.The results show that both the sur-face roughness and the depth of subsurface damage(SSD)are insensitive to grinding depth.The material removal rate can be increased sixfold by increasing the grinding depth,while the surface roughness and SSD depth increase by only about 10％.Moreover,it is found that the behavior of material removal is strongly dependent on grinding depth.As the grinding depth is increased,fibers are removed in smaller sizes,with the fiber length in chips being reduced by about 34％.However,too large a grinding depth will result in blockage by chip powder,which leads to a dramatic increase in the ratio of tangential to normal grinding forces.This study demonstrates that increasing the depth of cut is an effective approach to improve the machining efficiency of CMCs,while maintaining a good surface fin-ish.It provides the basis for the further development of high-performance grinding methods for CMCs,which should facilitate their wider application.
查看更多>>摘要：There is a currently a lack of large-area plasma sterilization devices that can intelligently identify the shape of a wound for automatic steriliza-tion.For this reason,in this work,a plasma sterilization device with wound-edge recognition was developed using a field-programmable gate array(FPGA)and a high-performance image-processing platform to realize intelligent and precise sterilization of wounds.SOLIDWORKS was used to design the mechanical structure of the device,and it was manufactured using 3D printing.The device used an improvement of the traditional Sobel detection algorithm,which extends the detection of edges in only the x and y directions to eight directions(00,45°,90°,135°,180°,225°,270°,and 315°),completing the wound-edge detection by adaptive thresholding.The device can be controlled according to different shapes of sterilization area to adjust the positioning of a single plasma-jet tube in the horizontal plane for two-dimensional move-ment;the distance between the plasma-jet tube and the surface of the object to be sterilized can be also adjusted in the vertical direction.In this way,motors are used to move the plasma jet and achieve automatic,efficient,and accurate plasma sterilization.It was found that a good sterilization effect could be achieved at both the culture-medium level and the biological-tissue level.The ideal sterilization parameters at the culture-medium level were a speed of 2 mm/s and a flow rate of 0.6 slm,while at the biological-tissue level,these values were 1 mm/s and 0.6 slm,respectively.
查看更多>>摘要：Nitrogen vacancy(NV)color centers in diamond have useful applications in quantum sensing and fluorescent marking.They can be gen-erated experimentally by ion implantation,femtosecond lasers,and chemical vapor deposition.However,there is a lack of studies of the yield of NV color centers at the atomic scale.In the molecular dynamics simulations described in this paper,NV color centers are pre-pared by ion implantation in diamond with pre-doped nitrogen and subsequent annealing.The differences between the yields of NV color centers produced by implantation of carbon(C)and nitrogen(N)ions,respectively,are investigated.It is found that C-ion implantation gives a greater yield of NV color centers and superior location accuracy.The effects of different pre-doping concentrations(400-1500 ppm)and implantation energies(1.0-3.0 keV)on the NV color center yield are analyzed,and it is shown that a pre-doping concentra-tion of 1000 ppm with 2 keV C-ion implantation can produce a 13％yield of NV color centers after 1600 K annealing for 7.4 ns.Finally,a brief comparison of the NV color center identification methods is presented,and it is found that the error rate of an analysis utiliz-ing the identify diamond structure+coordination analysis method is reduced by about 7％compared with conventional identification methods.
查看更多>>摘要：Solid-state nanopores offer a range of distinct advantages over biological nanopores,such as structural diversity and greater stability and durability;this makes them highly promising for high-resolution nanoparticle sensing.Biological nanopores can exhibit gating characteristics with stress-responsive switches and can demonstrate specificity toward particular molecules.Drawing inspiration from biological nanopores,this paper introduces a novel polymer nanopore with field-effect characteristics,leveraging a conductive polymer in its construction to show-case intriguing gating behavior.Notably,in this device,the polymer layer serves as the gate,enabling precise control over the source-drain current response inside and outside the pore by simply adjusting the gate voltage.This unique feature allows fine-tuning of the nanopore's sensitivity to nanoparticles of varying sizes and facilitates its operation in multiple modes.Experimental results reveal that the developed poly-mer nanopore field-effect transistor demonstrates remarkable selectivity in detecting nanoparticles of various sizes under different applied voltages.The proposed single device demonstrates the exceptional ability to detect multiple types of nanoparticle,showcasing its immense potential for a wide range of applications in biological-particle analysis and medical diagnostics.
查看更多>>摘要：Electron beam lithography(EBL)involves the transfer of a pattern onto the surface of a substrate by first scanning a thin layer of organic film(called resist)on the surface by a tightly focused and precisely controlled electron beam(exposure)and then selectively removing the exposed or nonexposed regions of the resist in a solvent(developing).It is widely used for fabrication of integrated cir-cuits,mask manufacturing,photoelectric device processing,and other fields.The key to drawing circular patterns by EBL is the graphics production and control.In an EBL system,an embedded processor calculates and generates the trajectory coordinates for movement of the electron beam,and outputs the corresponding voltage signal through a digital-to-analog converter(DAC)to control a deflector that changes the position of the electron beam.Through this procedure,it is possible to guarantee the accuracy and real-time con-trol of electron beam scanning deflection.Existing EBL systems mostly use the method of polygonal approximation to expose circles.A circle is divided into several polygons,and the smaller the segmentation,the higher is the precision of the splicing circle.However,owing to the need to generate and scan each polygon separately,an increase in the number of segments will lead to a decrease in the overall lithography speed.In this paper,based on Bresenham's circle algorithm and exploiting the capabilities of a field-programmable gate array and DAC,an improved real-time circle-producing algorithm is designed for EBL.The algorithm can directly generate cir-cular graphics coordinates such as those for a single circle,solid circle,solid ring,or concentric ring,and is able to effectively realizes deflection and scanning of the electron beam for circular graphics lithography.Compared with the polygonal approximation method,the improved algorithm exhibits improved precision and speed.At the same time,the point generation strategy is optimized to solve the blank pixel and pseudo-pixel problems that arise with Bresenham's circle algorithm.A complete electron beam deflection system is established to carry out lithography experiments,the results of which show that the error between the exposure results and the preset pat-terns is at the nanometer level,indicating that the improved algorithm meets the requirements for real-time control and high precision of EBL.
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