MXene-based flexible pressure sensor with piezoresistive properties significantly enhanced by atomic layer infiltration

The flexible pressure sensor has been credited for leading performance including higher sensitivity,faster response/recovery,wider detection range and higher mechanical durability,thus driving the development of novel sensing materials enabled by new processing technologies.Using atomic layer infiltration,Pt nanocrystals with dimensions on the order of a few nanometers can be infiltrated into the compressible lamellar structure of Ti3C2Tx MXene,allowing a modulation of its interlayer spacing,electrical conductivity and piezoresistive property.The flexible piezoresistive sensor is further developed from the Pt-infiltrated MXene on a paper substrate.It is demonstrated that Pt infiltration leads to a significant enhancement of the pressure-sensing performance of the sensor,including increase of sensitivity from 0.08 kPa^(-1)to 0.5 kPa^(-1),extension of detection limit from 5 kPa to 9 kPa,decrease of response time from 200 ms to 20 ms,and reduction of recovery time from 230 ms to 50 ms.The mechanical durability of the flexible sensor is also improved,with the piezoresistive performance stable over 1000 cycles of flexure fatigue.The atomic layer infiltration process offers new possibilities for the structure modification of MXene for advanced sensor applications.

Diffusion-tensor imaging as an adjunct to dynamic contrastenhanced MRI for improved accuracy of differential diagnosis between breast ductal carcinoma in situ and invasive breast carcinoma

Objective： To determine the value of diffusion-tensor imaging （DTI） as an adjunct to dynamic contrastenhanced magnetic resonance imaging （DCE-MRI） for improved accuracy of differential diagnosis between breast ductal carcinoma in situ （DCIS） and invasive breast carcinoma （IBC）. Methods： The MRI data of 63 patients pathologically confirmed as breast cancer were analyzed. The conventional MRI analysis metrics included enhancement style, initial enhancement characteristic, maximum slope of increase, time to peak, time signal intensity curve （TIC） pattern, and signal intensity on FS- T2WI. The values of apparent diffusion coefficient （ADC）, directionally-averaged mean diffusivity （D^vg）, exponential attenuation （EA）, fractional anisotropy （FA）, volume ratio （VR） and relative anisotropy （RA） were calculated and compared between DCIS and IBC. Multivariate logistic regression was used to identify independent factors for distinguishing IBC and DCIS. The diagnostic performance of the diagnosis equation was evaluated using the receiver operating characteristic （ROC） curve. The diagnostic efficacies of DCE- MRI, DWI and DTI were compared independently or combined. Results： EA value, lesion enhancement style and TIC pattern were identified as independent factor for differential diagnosis of IBC and DCIS. The combination diagnosis showed higher diagnostic efficacy than a single use of DCE-MRI （P=0.02）, and the area of the curve was improved from 0.84 （95% CI, 0.67-0.99） to 0.94 （95% CI, 0.85-1.00）. Conclusions： Quantitative DTI measurement as an adjunct to DCE-MRI could improve the diagnostic performance of differential diagnosis between DCIS and IBC compared to a single use of DCE-MRI.

Lead‑Free Perovskite Materials for Solar Cells

The toxicity issue of lead hinders large-scale commercial production and photovoltaic field application of lead halide perovskites.Some novel non-or low-toxic perovskite materials have been explored for development of environmentally friendly lead-free perovskite solar cells(PSCs).This review studies the substitution of equivalent/heterovalent metals for Pb based on first-principles calculation,summarizes the theoretical basis of lead-free perovskites,and screens out some promising lead-free candidates with suitable bandgap,optical,and electrical properties.Then,it reports notable achievements for the experimental studies of lead-free perovskites to date,including the crystal structure and material bandgap for all of lead-free materials and photovoltaic performance and stability for corresponding devices.The review finally discusses challenges facing the successful development and commercialization of lead-free PSCs and predicts the prospect of lead-free PSCs in the future.

Atomic level deposition to extend Moore’s law and beyond

In the past decades,Moore’s law drives the semiconductor industry to continuously shrink the critical size of transistors down to 7 nm.As transistors further downscaling to smaller sizes,the law reaches its limitation,and the increase of transistors density on the chip decelerates.Up to now,extreme ultraviolet lithography has been used in some key steps,and it is facing alignment precision and high costs for high-volume manufacturing.Meanwhile,the introduction of new materials and 3D complex structures brings serious challenges for top-down methods.Thus,bottom-up schemes are believed to be necessary methods combined with the top-down processes.In this article,atomic level deposition methods are reviewed and categorized to extend Moore’s law and beyond.Firstly,the deposition brings lateral angstrom resolution to the vertical direction as well as top-down etching,such as double patterning,transfer of nanowires,deposition of nanotubes,and so on.Secondly,various template-assisted selective deposition methods including dielectric templates,inhibitors and correction steps have been utilized for the alignment of 3D complex structures.Higher resolution can be achieved by inherently selective deposition,and the underlying selective mechanism is discussed.Finally,the requirements for higher precision and efficiency manufacturing are also discussed,including the equipment,integration processes,scale-up issues,etc.The article reviews low dimensional manufacturing and integration of 3D complex structures for the extension of Moore’s law in semiconductor fields,and emerging fields including but not limited to energy,catalysis,sensor and biomedicals.

原子层制造的研究现状与科学挑战

原子层制造是指加工精度达到原子层量级的可控制造技术,包括原子层去除、添加、迁移等。针对信息、能源、航空航天等领域核心零部件超高性能构建的发展需求,通过原子层可控去除制造全频段原子级精度无损表面,并结合原子层增材制造原子级新结构,有望实现特殊功能的有效创成,保证超高性能的安全可靠。另外,后摩尔时代先进芯片的制造工艺将迈入亚纳米物理极限,原子层制造需求贯穿芯片制造工艺的全流程。本文阐述了原子层制造技术的发展需求与研究进展,围绕原子层抛光、原子层沉积/刻蚀、原子层损伤控制、原子层工艺与装备等领域,梳理了原子层制造的发展方向及研究目标,凝练了原子层制造领域未来的关键科学问题及面临的挑战,探讨了前沿研究方向和发展战略。

A Predictive Instrument for Sensitive and Expedited Measurement of Ultra-Barrier Permeation

The reliable operation of flexible display devices poses a significant engineering challenge regarding the metrology of high barriers against water vapor.No reliable results have been reported in the range of 10–6 g∙(m^(2)∙d)1,and there is no standard ultra-barrier for calibration.To detect trace amount of water vapor permeation through an ultra-barrier with extremely high sensitivity and a greatly reduced test period,a predictive instrument was developed by integrating permeation models into high-sensitivity mass spectrometry measurement based on dynamic accumulation,detection,and evacuation of the permeant.Detection reliability was ensured by means of calibration using a standard polymer sample.After calibration,the lower detection limit for water vapor permeation is in the range of 10–7 g∙(m^(2)∙d)1,which satisfies the ultra-barrier requirement.Predictive permeation models were developed and evaluated using experimental data so that the steady-state permeation rate can be forecasted from non-steady-state results,thus enabling effective measurement of ultra-barrier permeation within a significantly shorter test period.

System identification and control of the ground operation mode of a hybrid aerial-ground robot

This paper presents an in-depth analytical and empirical assessment of the performance of DoubleBee,a novel hybrid aerial-ground robot.Particularly,the dynamic model of the robot with ground contact is analyzed,and the unknown parameters in the model are identified.We apply an unscented Kalman filter-based approach and a least square-based approach to estimate the parameters with given measurements and inputs at every time step.Real data are collected and used to estimate the parameters;test data verify that the values obtained are able to model the rotation of the robot accurately.A gain-scheduled feedback controller is proposed,which leverages the identified model to generate accurate control inputs to drive the system to the desired states.The system is proven to track a constant-velocity reference signal with bounded error.Simulations and real-world experiments using the proposed controller show improved performance than the PID-based controller in tracking step commands and maintaining attitude under robot movement.

Atomic layer deposition in advanced display technologies:from photoluminescence to encapsulation

Driven by the growing demand for next-generation displays,the development of advanced luminescent materials with exceptional photoelectric properties is rapidly accelerating,with such materials including quantum dots and phosphors,etc.Nevertheless,the primary challenge preventing the practical application of these luminescent materials lies in meeting the required durability standards.Atomic layer deposition(ALD)has,therefore,been employed to stabilize luminescent materials,and as a result,flexible display devices have been fabricated through material modification,surface and interface engineering,encapsulation,cross-scale manufacturing,and simulations.In addition,the appropriate equipment has been developed for both spatial ALD and fluidized ALD to satisfy the low-cost,high-efficiency,and high-reliability manufacturing requirements.This strategic approach establishes the groundwork for the development of ultra-stable luminescent materials,highly efficient light-emitting diodes(LEDs),and thin-film packaging.Ultimately,this significantly enhances their potential applicability in LED illumination and backlighted displays,marking a notable advancement in the display industry.

混合表面活性剂体系合成锆掺杂介孔分子筛

在水热体系中研究了以阳离子表面活性剂为主,阴离子表面活性剂、非离子表面活性剂、中性伯胺等为辅的混合表面活性剂对合成锆掺杂介孔分子筛的影响,考察了水/SiO2摩尔比、晶化温度、晶化时间及混合表面活性剂/SiO2摩尔比对所制分子筛结构的影响,对优化条件下合成的样品进行了表征.结果表明,锆掺杂介孔分子筛的最佳合成体系为阴阳离子表面活性剂混合体系,最佳合成配方为水/SiO2摩尔比58,混合表面活性剂/SiO2摩尔比0.15,100℃下晶化48h.最佳条件下合成的样品在小角区域有一个明显的衍射峰,表明其具有一定的长程有序性,晶面间距d=9.71nm,平均孔径为5.55nm,壁厚4.16nm,具有三维蠕虫状孔道结构,吸附亚甲基蓝、罗丹明B与甲基橙的混合溶液时,对亚甲基蓝的吸附选择性较好,吸附率达90.24%.

Ordered mesoporous NiFe_2O_4 with ultrathin framework for low-ppb toluene sensing

Highly sensitive and selective detection against specific target gases,especially at low-ppb(part per billion)level,remain a great number of challenges in gas sensor applications.In this paper,we first present an ordered mesoporous NiFe_2O_4 for highly sensitive and selective detection against low-ppb toluene.A series of mesoporous NiFe_2O_4 materials were synthesized by templating from mesoporous silica KIT-6 and its framework thickness was reduced from 8.5 to 5 nm by varying the pore size of KIT-6 from 9.4 to 5.6 nm,accompanied with the increase of the specific surface area from 134 to 216 m^2g^(-1).The ordered mesoporous NiFe_2O_4 with both ultrathin framework of 5 nm and large specific surface area of up to 216 m^2g^(-1)exhibits a highest response(R_(gas)/R_(air)-1=77.3)toward 1,000 ppb toluene at 230℃ and is nearly 7.3 and 76.7 times higher than those for the NiFe_2O_4 replica with thick framework and its bulk counterpart respectively,which also possesses a quite low limit of detection(<2 ppb),and good selectivity.

基于原子层沉积技术的纳米颗粒表面改性方法

在原子尺度制造方法中,原子层沉积(ALD)是一种依靠表面自限制吸附反应沉积超薄膜的技术,具有优异的制造精度、保型性和沉积均匀一致性等独特优势.本文介绍了ALD技术在纳米颗粒表面改性的最新进展及应用.通过ALD工艺调控可以精准制备致密包覆层,多孔包覆层以及表面定向改性构型.纳米级致密包覆层可以隔绝外界环境,提升颗粒稳定性,同时保留颗粒本体性能.多孔包覆层则具有纳米通道,在保留颗粒与外界接触的同时,实现了对进入反应物尺寸的筛选,以及提供了物理限域作用增强稳定性.表面定向改性则能够选择性钝化或者暴露纳米颗粒特定功能表面.ALD的颗粒表面改性技术在电极材料、含能与磁性颗粒的稳定化,催化剂活性位点定向调控等方面具有前瞻性应用.最后,文章展望了ALD进行微纳颗粒表面改性未来面临的挑战和发展方向.

Silicone/graphene oxide co-cross-linked aerogels with wide-temperature mechanical flexibility,super-hydrophobicity and flame resistance for exceptional thermal insulation and oil/water separation

Development of multifunctional and high-performance silicone aerogel is highly required for various promising applications.However,unstable cross-linking structure and poor thermal stability of silicone network as well as complicated processing restrict the practical use significantly.Herein,we report a facile and versatile ambient drying strategy to fabricate lightweight,wide-temperature flexible,super-hydrophobic and flame retardant silicone composite aerogels modified with low-content functionalized graphene oxide(FGO).After optimizing silane molecules,incorporation ofγ-aminopropyltriethoxysilane functionalization is found to promote the dispersion stability of GO during the hydrolysis-polymerization process and thus produce the formation of unique strip-like co-cross-linked network.Consequently,the aerogels containing∼2.0 wt%FGO not only possess good cyclic compressive stability under strain of 70%for 100 cycles and outstanding mechanical reliability in wide temperature range(from liquid nitrogen to 350℃),but also display excellent flame resistance and super-hydrophobicity.Further,the optimized silicone/FGO aerogels display exceptional thermal insulating performance superior to pure aerogel and hydrocarbon polymer foams,and they also show efficient oil absorption and separation capacity for var-ious solvents and oil from water.Clearly,this work provides a new route for the rational design and development of advanced silicone composite aerogels for multifunctional applications.

Marine aquaculture mapping using GF-1 WFV satellite images and full resolution cascade convolutional neural network

Growing demand for seafood and reduced fishery harvests have raised intensive farming of marine aquaculture in coastal regions,which may cause severe coastal water problems without adequate environmental management.Effective mapping of mariculture areas is essential for the protection of coastal environments.However,due to the limited spatial coverage and complex structures,it is still challenging for traditional methods to accurately extract mariculture areas from medium spatial resolution(MSR)images.To solve this problem,we propose to use the full resolution cascade convolutional neural network(FRCNet),which maintains effective features over the whole training process,to identify mariculture areas from MSR images.Specifically,the FRCNet uses a sequential full resolution neural network as the first-level subnetwork,and gradually aggregates higher-level subnetworks in a cascade way.Meanwhile,we perform a repeated fusion strategy so that features can receive information from different subnetworks simultaneously,leading to rich and representative features.As a result,FRCNet can effectively recognize different kinds of mariculture areas from MSR images.Results show that FRCNet obtained better performance than other classical and recently proposed methods.Our developed methods can provide valuable datasets for large-scale and intelligent modeling of the marine aquaculture management and coastal zone planning.

Stable and Efficient Red Perovskite Light-Emitting Diodes Based on Ca^(2+)-Doped CsPbI_(3) Nanocrystals

α-CsPbI3 nanocrystals(NCs)with poor stability prevent their wide applications in optoelectronic fields.Ca^(2+)(1.00Å)as a new B-site doping ion can successfully boost CsPbI3 NC performance with both improved phase stability and optoelectronic properties.With a Ca^(2+)/Pb^(2+)ratio of 0.40%,both phase and photoluminescence(PL)stability could be greatly enhanced.Facilitated by increased tolerance factor,the cubic phase of its solid film could be maintained after 58 days in ambient condition or 4 h accelerated aging process at 120℃.The PL stability of its solution could be preserved to 83%after 147 days in ambient condition.Even using UV light to accelerate aging,the T_(50) of PL could boost 1.8-folds as compared to CsPbI_(3) NCs.Because Ca^(2+) doping can dramatically decrease defect densities of films and reduce hole injection barriers,the red light-emitting diodes(LEDs)exhibited about triple enhancement for maximum the external quantum efficiency(EQE)up to 7.8%and 2.2 times enhancement for half-lifetime of LED up to 85 min.We believe it is promising to further explore high-quality CsPbI_(3) NC LEDs via a Ca^(2+)-doping strategy.

Advances in Atomic Layer Deposition

Atomic layer deposition(ALD)is a thin-film fabrication technique that has great potential in nanofabrication.Based on its self-limiting surface reactions,ALD has excellent conformality,sub-nanometer thickness control,and good process compatibility.These merits promote the industrial and research applications of ALD in various fields.This article provides an introduction to ALD and highlights its applications in semiconductors,pan-semiconductors,environment and energy,and other fields.The applications of ALD in the key nodes of integrated circuits are initially demonstrated,and the areaselective ALD technique is discussed as a bottom-up method for self-aligned nanomanufacturing.Emerging applications of ALD are illustrated in the fabrication of passivation layers,functional surface layers,and buffer layers,which have shown the development trend of ALD in miniaturization and diversification.ALD is an enabling technique for atomic and closeto-atomic scale manufacturing(ACSM)of materials,structures,devices,and systems in versatile applications.The use of theory calculation,multiscale simulation,and more novel methods would steer ALD into further evolution,which makes it possible to cater to the demand of ACSM.

Distributed multi-robot sweep coverage for a region with unknown workload distribution

This paper considers the scenario where multiple robots collaboratively cover a region in which the exact distribution of workload is unknown prior to the operation.The workload distribution is not uniform in the region,meaning that the time required to cover a unit area varies at different locations of the region.In our approach,we divide the target region into multiple horizontal stripes,and the robots sweep the current stripe while partitioning the next stripe concurrently.We propose a distributed workload partition algorithm and prove that the operation time on each stripe converges to the minimum under the discrete-time update law.We conduct comprehensive simulation studies and compare our method with the existing methods to verify the theoretical results and the advantage of the proposed method.Flight experiments on mini drones are also conducted to demonstrate the practicality of the proposed algorithm.

Micellar Catalysis:Visible-Light Mediated Imidazo[1,2-a]pyridine C—H Amination with N-Aminopyridinium Salt Accelerated by Surfactant in Water

A light-promoted metal-free protocol for the amination of imidazo[1,2-a]pyridines with N-aminopyridinium salt by the assistance of surfactants in water was reported,charactering mild and environmentally benign conditions,as well as great functional group tolerance.Micelles with negatively charged polar surface and hydrophobic core formed from sodium dodecyl sulfate serve as an ideal medium for visible-light mediated radical reaction of cationic pyridine salt and imidazo[1,2-a]pyridine in aqueous phase.The electrostatic interaction between positively charged N-aminopyridinium and negatively charged surface of micelles is of great significance in this method.

Structure and magnetic properties of the S=3/2 zigzag spin chain antiferromagnet BaCoTe_(2)O_(7)

We report a study of the structure and magnetic properties of the S=3/2 zigzag spin chain compound BaCoTe_(2)O_(7).Neutron diffraction measurements show that it crystallizes in the noncentrosymmetric space group Ama2 with a canted↑↑↓↓spin structure along the quasi-one-dimensional zigzag chain and a moment size of 1.89(2)μBat 2 K.Both magnetic susceptibility and specific heat measurements yield an antiferromagnetic phase transition at TN=6.2 K.A negative Curie-Weiss temperature,ΘCW=-74.7(2) K,and an empirical frustration parameter,f=|ΘCW|/TN≈12,are obtained by fitting the magnetic susceptibility,indicating antiferromagnetic interactions and strong magnetic frustration.From ultraviolet-visible absorption spectroscopy and first-principles calculations,an indirect band gap of 2.68(2) eV is determined.We propose that the canted zigzag spin chain of BaCoTe_(2)O_(7) may produce a change in the polarization via the exchange-striction mechanism.

Stable and Efficient Red Perovskite Light-Emitting Diodes Based on Ca^(2+)-Doped CsPbI_(3)Nanocrystals

α-CsPbI_(3)nanocrystals(NCs)with poor stability prevent their wide applications in optoelectronic fields.Ca^(2+)(1.00Å)as a new B-site doping ion can successfully boost CsPbI_(3)NC performance with both improved phase stability and optoelectronic properties.With a Ca^(2+)/Pb^(2+)ratio of 0.40%,both phase and photoluminescence(PL)stability could be greatly enhanced.Facilitated by increased tolerance factor,the cubic phase of its solid film could be maintained after 58 days in ambient condition or 4 h accelerated aging process at 120℃.The PL stability of its solution could be preserved to 83%after 147 days in ambient condition.Even using UV light to accelerate aging,the T50 of PL could boost 1.8-folds as compared to CsPbI_(3)NCs.Because Ca^(2+)doping can dramatically decrease defect densities of films and reduce hole injection barriers,the red light-emitting diodes(LEDs)exhibited about triple enhancement for maximum the external quantum efficiency(EQE)up to 7.8%and 2.2 times enhancement for half-lifetime of LED up to 85 min.We believe it is promising to further explore high-quality CsPbI_(3)NC LEDs via a Ca^(2+)-doping strategy.