Efficient concentration of trace analyte with ordered hotspot construction for a robust and sensitive SERS platform

Surface-enhanced Raman scattering(SERS)platform,which enables trace analyte detection,has important application prospects.By structuring/modifying the surface of the SERSsubstrate,analyte in highly diluted solutions can be concentrated into localized active areas for highly sensitive detection.However,subject to the difficulty of the fabrication process,itremains challenging to balance hot-spot construction and the concentration capacity of analyte simultaneously.Therefore,preparing SERS substrates with densely ordered hot spots andefficient concentration capacity is of great significance for highly sensitive detection.Herein,we propose an Ag and fluoroalkyl-modified hierarchical armour substrate(Ag/F-HA),which has a double-layer stacking design to combine analyte concentration with hotspot construction.The microarmour structure is fabricated by femtosecond-laser processing to serve as asuperhydrophobic and low-adhesive surface to concentrate analyte,while the anodic aluminium oxide(AAO)template creates a nanopillar array serving as dense and ordered hot spots.Under the synergistic action of hot spots and analyte concentration,Ag/F-HA achieves a detectionlimit down to 10^(-7)M doxorubicin(DOX)molecules with a RSD of 7.69%.Additionally,Ag/F-HA exhibits excellent robustness to resist external disturbances such as liquid splash or abrasion.Based on our strategy,SERS substrates with directional analyte concentrations are further explored by patterning microcone arrays with defects.This work opens a way to the realistic implementation of SERS in diverse scenarios.

Femtosecond laser direct writing of functional stimulus-responsive structures and applications

Diverse natural organisms possess stimulus-responsive structures to adapt to the surrounding environment.Inspired by nature,researchers have developed various smart stimulus-responsive structures with adjustable properties and functions to address the demands of ever-changing application environments that are becoming more intricate.Among many fabrication methods for stimulus-responsive structures,femtosecond laser direct writing(FsLDW)has received increasing attention because of its high precision,simplicity,true three-dimensional machining ability,and wide applicability to almost all materials.This paper systematically outlines state-of-the-art research on stimulus-responsive structures prepared by FsLDW.Based on the introduction of femtosecond laser-matter interaction and mainstream FsLDW-based manufacturing strategies,different stimulating factors that can trigger structural responses of prepared intelligent structures,such as magnetic field,light,temperature,pH,and humidity,are emphatically summarized.Various applications of functional structures with stimuli-responsive dynamic behaviors fabricated by FsLDW,as well as the present obstacles and forthcoming development opportunities,are discussed.

The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner

With the development of cutting-edge multi-object spectrographs,fiber positioners located in the focal plane are being scaled down in size,and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper motors.However,the small electrical time constant of such coreless motors poses a challenge,as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been tricky.To overcome this challenge,it is advised to increase the Pulse Width Modulation(PWM)frequency as much as possible to mitigate the effects of the current fluctuation.This must be done while ensuring adequate resolution of the PWM generator.By employing a voltage open-loop field-oriented control based on a modulation frequency of 1 MHz,the drive current only costs 25 m A under a 3.3 V power supply.The sine degree of phase current is immaculate,and the repeat positioning accuracy can reach 2μm.Moreover,it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board,especially in sizesensitive applications.This device has been developed under the new generation of The Large Sky Area MultiObject Fiber Spectroscopic Telescope.

Ground-Based Hyperspectral Stereoscopic Remote Sensing Network: A Promising Strategy to Learn Coordinated Control of O_(3) and PM_(2.5) over China

With the coming of the“14th Five-Year Plan,”the coordinated control of particulate matter with an aerodynamic diameter no greater than 2.5 lm(PM_(2.5))and O_(3) has become a major issue of air pollution prevention and control in China.The stereoscopic monitoring of regional PM_(2.5) and O_(3) and their precursors is crucial to achieve coordinated control.However,current monitoring networks are currently inadequate for monitoring the vertical profiles of both PM_(2.5) and O_(3) simultaneously and support air quality control.The University of Science and Technology of China(USTC)has established a nationwide ground-based hyperspectral stereoscopic remote sensing network based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)since 2015.This monitoring network provides a significant opportunity for the regional coordinated control of PM_(2.5) and O_(3) in China.One-year vertical profiles of aerosol,NO_(2) and HCHO monitored from four MAX-DOAS stations installed in four megacities(Beijing,Shanghai,Shenzhen,and Chongqing)were used to characterize their vertical distribution differences in four key regions,Jing–Jin–Ji(JJJ),Yangtze River Delta(YRD),Pearl River Delta(PRD),and Sichuan Basin(SB),respectively.The normalized and yearly averaged aerosol vertical profiles below 400 m in JJJ and PRD exhibit a box shape and a Gaussian shape,respectively,and both show exponential shapes in YRD and SB.The NO_(2) vertical profiles in four regions all exhibit exponential shapes because of vehicle emissions.The shape of the HCHO vertical profile in JJJ and PRD was Gaussian,whereas an exponential shape was shown in YRD and SB.Moreover,a regional transport event occurred at an altitude of 600–1000 m was monitored in the southwest–northeast pathway of the North China Plain(NCP)by five MAX-DOAS stations(Shijiazhuang(SJZ),Wangdu(WD),Nancheng(NC),Chinese Academy of Meteorological Sciences(CAMS),and University of Chinese Academy of Sciences(UCAS))belonging to the above network.The aerosol optical depths(AOD)in these five stations decreased in the order of SJZ>WD>NC>CAMS>UCAS.The short-distance regional transport of NO2 in the 700–900 m layer was monitored between WD and NC.As an important precursor of secondary aerosol,the peak of NO_(2) air mass in WD and NC all occurred 1 h earlier than that of aerosol.This was also observed for the short-distance regional transport of HCHO in the 700–900 m layer between NC and CAMS,which potentially affected the O_(3) concentration in Beijing.Finally,CAMS was selected as a typical site to determine the O_(3)–NO_(x)–volatile organic compounds(VOCs)sensitivities in vertical space.We found the production of O_(3) changed from predominantly VOCs-limited conditions to mainly mixed VOCs–NO_(x)-limited condition from the 0–100 m layer to the 200–300 m layer.In addition,the downward transport of O_(3) could contribute to the increase of ground surface O_(3) concentration.This ground-based hyperspectral stereoscopic remote sensing network provide a promising strategy to support management of PM_(2.5) and O_(3) and their precursors and conduct attribution of sources.

Adjacent mode resonance of a hydraulic pipe system consisting of parallel pipes coupled at middle points

The coupling vibration of a hydraulic pipe system consisting of two pipes is studied.The pipes are installed in parallel and fixed at their ends,and are restrained by clips to one bracket at their middle points.The pipe subjected to the basement excitation at the left end is named as the active pipe,while the pipe without excitation is called the passive pipe.The clips between the two pipes are the bridge for the vibration energy.The adjacent natural frequencies will enhance the vibration coupling.The governing equation of the coupled system is deduced by the generalized Hamilton principle,and is discretized to the modal space.The modal correction is used during the discretization.The investigation on the natural characters indicates that the adjacent natural frequencies can be adjusted by the stiffness of the two clips and bracket.The harmonic balance method(HBM)is used to study the responses in the adjacent natural frequency region.The results show that the vibration energy transmits from the active pipe to the passive pipe swimmingly via the clips together with a flexible bracket,while the locations of them are not node points.The adjacent natural frequencies may arouse wide resonance curves with two peaks for both pipes.The stiffness of the clip and bracket can release the vibration coupling.It is suggested that the stiffness of the clip on the passive pipe should be weak and the bracket should be strong enough.In this way,the vibration energy is reflected by the almost rigid bracket,and is hard to transfer to the passive pipe via a soft clip.The best choice is to set the clips at the pipe node points.The current work gives some suggestions for weakening the coupled vibration during the dynamic design of a coupled hydraulic pipe system.

Fault Diagnosis of the LAMOST Fiber Positioner Based on a Long Short-term Memory(LSTM)Deep Neural Network

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)has been in normal operation for more than 10 yr,and routine maintenance is performed on the fiber positioner every summer.The positioning accuracy of the fiber positioner directly affects the observation performance of LAMOST,and incorrect fiber positioner positioning accuracy will not only increase the interference probability of adjacent fiber positioners but also reduces the observation efficiency of LAMOST.At present,during the manual maintenance process of the positioner,the fault cause of the positioner is determined and analyzed when the positioning accuracy does not meet the preset requirements.This causes maintenance to take a long time,and the efficiency is low.To quickly locate the fault cause of the positioner,the repeated positioning accuracy and open-loop calibration curve data of each positioner are obtained in this paper through the photographic measurement method.Based on a systematic analysis of the operational characteristics of the faulty positioner,the fault causes are classified.After training a deep learning model based on long short-term memory,the positioner fault causes can be quickly located to effectively improve the efficiency of positioner fault cause analysis.The relevant data can also provide valuable information for annual routine maintenance methods and positioner designs in the future.The method of using a deep learning model to analyze positioner operation failures introduced in this paper is also of general significance for the maintenance and design optimization of fiber positioners using a similar double-turn gear transmission system.

Experimental research and analysis of three-finger micro-tweezers

A new type of three-finger micro-tweezer driven by electro-static force was developed for stable manipulation and assembly of micro devices. The whole system consists of micro-tweezers and a specially designed high frequency AC power supply. The free end of the fingers closes and opens with the increase and decrease of the voltage. The tweezers can grasp and manipulate micro objects at size from 30～100 μm. A quantitative simulation method based on boundarx element method(BEM) and equation of energy conservation is introduced to analyze the non-linear behaviors of the tweezer closure. The simulation results agree well with the experimental data.

Number and Distribution of Fiducial Fibers in a Spectroscopic Survey Telescope

To date,the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)has been in operation for 12 yr.To improve the telescope's astronomical observation accuracy,the original open-loop fiber positioning system of LAMOST is in urgent need of upgrading.The upgrade plan is to install several fiber view cameras(FVCs)around primary mirror B to build a closed-loop feedback control system.The FVCs are 20 m from the focal surface.To reduce a series of errors when the cameras detect the positions of the optical fibers,we designed fiducial fibers on the focal surface to be fiducial points for the cameras.Increasing the number of fiducial fibers can improve the detection accuracy of the FVC system,but it will also certainly reduce the number of fiber positioners that can be used for observation.Therefore,the focus of this paper is how to achieve the quantity and distribution that meet the requirements of system detection.In this paper,we introduce the necessity of using fiducial fibers,propose a method for selecting their number and present several methods for assessing the uniformity of their distribution.Finally,we implement particle swarm optimization to find the best distribution of fiducial fibers.

A digital microfluidic single-cell manipulation systemoptimized by extending-depth-of-field device

Microfuidic systems have been widely utilized in high-throughput biology analysis,but thedificulties in iquid manipulation and cell cultivation limit its application.This work has developed a new digital microfluidic(DMF)system for on-demand droplet control.By adopting anextending-depth-of-field(EDoF)phase modulator to the optical system,the entire depth of themicrofluidic channel can be covered in one image without any refocusing process,ensuring that 95%of the particles in the droplet are captured within three shots together with shaking pro-cesses.With this system,suspension droplets are generated and droplets containing only oneyeast cll can be recognized,then each single cell is cultured in the array of the chip.Byobservingtheir growth in cell numbers and the green fluorescence protein(GFP)production via fluorescence imaging,the single cell with the highest production can be identified.The results haveproved the heterogeneity of yeast cells,and showed that the combined system can be applied forrapid single-cell sorting,cultivation,and analysis.

Triboelectric‘electrostatic tweezers'for manipulating droplets on lubricated slippery surfaces prepared by femtosecond laser processing

The use of‘Electrostatic tweezers'is a promising tool for droplet manipulation,but it faces many limitations in manipulating droplets on superhydrophobic surfaces.Here,we achieve noncontact and multifunctional droplet manipulation on Nepenthes-inspired lubricated slippery surfaces via triboelectric electrostatic tweezers(TETs).The TET manipulation of droplets on a slippery surface has many advantages over electrostatic droplet manipulation on a superhydrophobic surface.The electrostatic field induces the redistribution of the charges inside the neutral droplet,which causes the triboelectric charged rod to drive the droplet to move forward under the electrostatic force.Positively or negatively charged droplets can also be driven by TET based on electrostatic attraction and repulsion.TET enables us to manipulate droplets under diverse conditions,including anti-gravity climb,suspended droplets,corrosive liquids,low-surface-tension liquids(e.g.ethanol with a surface tension of 22.3 mN·m^(-1)),different droplet volumes(from 100 nl to 0.5 ml),passing through narrow slits,sliding over damaged areas,on various solid substrates,and even droplets in an enclosed system.Various droplet-related applications,such as motion guidance,motion switching,droplet-based microreactions,surface cleaning,surface defogging,liquid sorting,and cell labeling,can be easily achieved with TETs.

从中国首台紫外-可见光高光谱卫星仪器反演得到的高空间分辨率臭氧廓线

Understanding the vertical distribution of ozone is crucial when assessing both its horizontal and vertical transport,as well as when analyzing the physical and chemical properties of the atmosphere.One of the most effective ways to obtain high spatial resolution ozone profiles is through satellite observations.The Environmental Trace Gases Monitoring Instrument(EMI)deployed on the Gaofen-5 satellite is the first Chinese ultraviolet-visible hyperspectral spectrometer.However,retrieving ozone profiles using backscattered radiance values measured by the EMI is challenging due to unavailable measurement errors and a low signal-to-noise ratio.The algorithm developed for the Tropospheric Monitoring Instrument did not allow us to retrieve 87%of the EMI pixels.Therefore,we developed an algorithm specific to the characteristics of the EMI.The fitting residuals are smaller than 0.3%in most regions.The retrieved ozone profiles were in good agreement with ozonesonde data,with maximum mean biases of 20%at five latitude bands.By applying EMI averaging kernels to the ozonesonde profiles,the integrated stratospheric column ozone and tropospheric column ozone also showed excellent agreement with ozonesonde data,The lower layers(0-7.5 km)of the EMI ozone profiles reflected the seasonal variation in surface ozone derived from the China National Environmental Monitoring Center(CNEMC).However,the upper layers(9.7-16.7 km)of the ozone profiles show different trends,with the ozone peak occurring at an altitude of 9.7-16.7 km in March,2019.A stratospheric intrusion event in central China from August 11 to 15,2019,is captured using the EMI ozone profiles,potential vorticity data,and relative humidity data.The increase in the CNEMC ozone co ncentration showed that downward transport enhanced surface ozone pollution.

High-performance liquid metal electromagnetic actuator fabricated by femtosecond laser

Small-scale electromagnetic soft actuators are characterized by a fast response and simplecontrol,holding prospects in the field of soft and miniaturized robotics.The use of liquid metal(LM)to replace a rigid conductor inside soft actuators can reduce the rigidity and enhance the actuation performance and robustness.Despite research efforts,challenges persist in the flexible fabrication of LM soft actuators and in the improvement of actuation performance.To address these challenges,we developed a fast and robust electromagnetic soft microplate actuator based on a laser-induced selective adhesion transfer method.Equipped with unprecedentedly thin LM circuit and customized low Young’s modulus silicone rubber(1.03 kPa),our actuator exhibits an excellent deformation angle(265.25?)and actuation bending angular velocity(284.66 rad·s^(-1)).Furthermore,multiple actuators have been combined to build an artificial gripper with a wide range of functionalities.Our actuator presents new possibilities for designing small-scaleartificial machines and supports advancements in ultrafast soft and miniaturized robotics.

MAX-DOAS and in-situ measurements of aerosols and trace gases over Dongying,China:Insight into ozone formation sensitivity based on secondary HCHO

This study presents a comprehensive overview of the atmospheric pollutants including Sulfur dioxide(SO_(2)),Nitrogen dioxide(NO_(2)),Formaldehyde(HCHO),Particulate Matter PM;PM_(10):diameter≤10μm,and PM_(2.5):diameter≤2.5μm,and Ozone(O_(3)),over Dongying(Shandong Province)from March-April 2018 and September-October 2019 by employing ground-based Multiple Axis Differential Optical Absorption Spectroscopy(MAX-DOAS)observations along with the in-situ measurements attained by the national air quality monitoring platform.The concentrations of SO_(2)and NO_(2)were under the acceptable level,while both PM_(2.5),and PM_(10)were higher than the safe levels as prescribed by national and international air quality standards.The results depict that 21%of the total observation days were found to be complex polluted days(PM_(2.5)>35μg/m^(3) and O_(3)>160μg/m^(3)).The secondary HCHO was used for accurate analysis of O_(3)sensitivity.A difference of 11.40%and 10%during March-April 2018 and September-October 2019 respectively in O_(3)sensitivity was found between HCHO_(total)/NO_(2)and HCHO_(sec)/NO_(2).The results indicate that primary HCHO have significant contribution in HCHO.O_(3)formation predominantly remained to be in VOC-limited and transitional regime during March-April 2018 and September-October 2019 in Dongying.These results imply that concurrent control of both NO_(x) and VOCs would benefit in ozone reductions.Additionally,the criteria pollutants(PM,SO_(2),and NO_(2))depicted strong correlations with each other except for O_(3)for which weak correlation coefficient was obtained with all the species.This study will prove to be baseline for designing of air pollution control strategies.

Magnetically responsive manipulation of droplets and bubbles

Droplets and bubbles have a wide range of applications in industry,agriculture,and daily life,and their controllable manipulation is of significant scientific and technological importance.Versatile magnetically responsive manipulation strategies have been developed to achieve precise control over droplets and bubbles.To manipulate nonmagnetic droplets or bubbles with magnetic fields,the presence of magnetic medium is indispensable.Magnetic additives can be added to the surface or interior of droplets and bubbles,allowing for on-demand manipulation by direct magnetic actuation.Alternatively,magnetically responsive elastomer substrates can be used to actuate droplets and bubbles by controlling the deformation of microstructures on the substrates through magnetic stimulation.Another strategy is based on untethered magnetic devices,which enables free mobility,facilitating versatile manipulation of droplets and bubbles in a flexible manner.This paper reviews the advances in magnetically responsive manipulation strategies from the perspective of droplets and bubbles.An overview of the different classes of magnetic medium,along with their respective corresponding droplet/bubble manipulation methods and principles,is first introduced.Then,the applications of droplet/bubble manipulation in biomedicine,microchemistry,and other fields are presented.Finally,the remaining challenges and future opportunities related to regulating droplet/bubble behavior using magnetic fields are discussed.

Parametric Research of Experiments on a Carangiform Robotic Fish

In this paper, a carangiform robotic fish with 4-DoF （degree of freedom） tail has been developed. The robotic fish has capability of swimming under two modes that are radio control and autonomous swimming. Experiments were conducted to investigate the influences of characteristic parameters including the frequency, the amplitude, the wave length, the phase difference and the coefficient on forward velocity. The experimental results shown that the swimming performance of the robotic fish is affected mostly by the characteristic parameters observed.

Numerical and Experimental Research on Modular Oscillating Fin

Fishes are famous for their ability to position themselves accurately even in turbulent flows. This ability is the result of the coordinated movement of fins which extend from the body. We have embarked on a research program designed to develop an agile and high efficient biologically inspired robotic fish based on the performance of hybrid mechanical fms. To accomplish this goal, a mechanical ray-like fin actuated by Shape Memory Alloy （SMA） is developed, which can realize both oscillatory locomotion and undulatory locomotion. We first give a brief introduction on the mechanical structure of our fin and then carry out theoretic analysis on force generation. Detailed information of these theoretical results is later revealed by Computational Huid Dynamic （CFD）, and is final validated by experiments. This robotic fin has potential application as a propulsor for future underwater vehicles in addition to being a valuable scientific instrument.

ROBOT'S MOTION ERROR AND ONLINE COMPENSATION BASED ON FORCE SENSOR

Robot＇s dynamic motion error and on-line compensation based on multi-axis force sensor are dealt with.It is revealed that the reasons of the error are formed and the relations of the error are delivered.A motion equation of robot＇s termination with the error is established,and then,an error matrix and an error compensation matrix of the motion equation are also defined.An on-line error＇s compensation method is put forward to decrease the displacement error,which is a degree of millimeter,shown by the result of simulation of PUMA562 robot.

Recent developments in photoacoustic imaging and sensing for nondestructive testing and evaluation

Photoacoustic(PA)imaging has been widely used in biomedical research and preclinical studies during the past two decades.It has also been explored for nondestructive testing and evaluation(NDT/E)and for industrial applications.This paper describes the basic principles of PA technology for NDT/E and its applications in recent years.PA technology for NDT/E includes the use of a modulated continuous-wave laser and a pulsed laser for PA wave excitation,PA-generated ultrasonic waves,and all-optical PA wave excitation and detection.PA technology for NDT/E has demonstrated broad applications,including the imaging of railway cracks and defects,the imaging of Li metal batteries,the measurements of the porosity and Young’s modulus,the detection of defects and damage in silicon wafers,and a visualization of underdrawings in paintings.

Encryption/decryption and microtarget capturing by pH-driven Janus microstructures fabricated by the same femtosecond laser printing parameters

Several natural organism can change shape under external stimuli. These natural phenomena have inspired a vast amount of research on exploration and implementation of reconfigurable shape transformation. The Janus structure is a promising approach to achieve shape transformation based on its heterogeneous chemical or physical properties on opposite sides.However, the heterogeneity is generally realized by multi-step processing, different materials,and/or different processing parameters. Here, we present a simple and flexible method of producing p H-sensitive Janus microactuators from a single material, using the same laser printing parameters. These microactuators exhibit reversible structural deformations with large bending angles of ~31°and fast response(~0.2 s) by changing the p H value of the aqueous environment. Benefited from the high flexibility of the laser printing technique and the spatial arrangements, pillar heights, and bending directions of microactuators are readily controlled,enabling a variety of switchable ordered patterns and complex petal-like structures on flat surfaces and inside microchannels. Finally, we explore the potential applications of this method in information encryption/decryption and microtarget capturing.

Correction to: Recent developments in photoacoustic imaging and sensing for nondestructive testing and evaluation

Following publication of the original article[1],the authors identified an error in the article title.The first word ‘Review’ is added mistakenly by the typesetter.