磁性修饰的镧系上转换纳米晶体应用于指纹信息识别

新型磁性荧光材料的开发对鉴定和刑事侦查具有重要意义。由于传统相机中使用的光敏元件在500~700nm范围内表现出最高的量子效率,因此以507~533 nm、533~568 nm和637~683 nm为主发射峰的镧系上转换纳米粒子(UCNPs)适合用于构建磁性荧光材料。本文通过配体连接的方法证实了一种磁性上转换纳米颗粒—NaGdF_(4):Yb,Er-Fe_(3)O_(4)。在优化反应参数后,复合颗粒获得了优异的磁性能和上转换荧光强度,并且可在各种基底上实现高对比度的潜在指纹识别。得益于上转换发光与磁性的结合,指纹识别具有了高灵敏度与通用性。

Research on the construction path of the megacity from the perspective of Nudge Theory:Empirical evidence of the“Park City”construction in Chengdu Tianfu New Area

The transformation of Chengdu Tianfu New Area,a state-level new district,from the first site of constructing the“Park City”to the representative of the“Park City”,contains a unique path of“Chinese Style Governance”.To expand the diverse paths of constructing megacities,the current research references the nudge theory of behavioral science,adopts the extended case method,and takes Chengdu Tianfu New Area as a typical case to summarize the“nudge”path of“Party City”construction.The study found that the government achieves the lock-in effect by the priming mechanism and uses the nudge strategy of improving environment and guiding public opinion,thereby helping the people make free choices.It realizes the framework effect by the salience mechanism and uses the strategies of highlighting key information and optimizing information delivery methods,which directly affects the behavior of the public.It achieves the commitment effect by the comparison mechanism,including the horizontal comparison and vertical comparison strategies,and gradually realizes the policy goals.It realizes the social norm effect by the imitation mechanism and uses the strategies of creating peer pressure and playing celebrity effect,which in turn influence people’s choices.With the help of the“nudging”mechanism,the construction of the park city has realized the interactive cycle of“government output-citizen feedback”and achieved the goal of“making great change through small actions”.As a new behavioral intervention tool,“nudging”provides an alternative explanation for the construction of the park city in Tianfu New Area and opens up new ideas for the construction of megacities.This study concludes that the construction of megacities can achieve the goal of“common return”through different ways and provides practical inspiration for future urban construction.

Flexible and breathable 3D porous SSE/MXene foam towards impact/electromagnetic interference/bacteria multiple protection performance for intelligent wearable devices

As intelligent wearable devices,they will inevitably be subjected to various damages and disturbances from the external environment during daily use.Therefore,it is urgent to develop safeguarding materials with multiple protective properties.Herein,this work developed a flexible and breathable three-dimensional(3D)porous shear stiffening elastomer(SSE)/MXene(M-SSE)foam with impact/electromagnetic interference(EMI)/bacteria multiple protection performance for intelligent wearable devices.The continuous conductive MXene network in the 3D SSE porous structure made M-SSE foam exhibit excellent electromagnetic interference shielding property with a high shielding effectiveness of 34 dB.Attributed to the shear stiffening effect of porous SSE matrix,M-SSE foam possessed unique anti-impact and protection properties.The energy dissipation rate reached up to more than 85%,illustrating M-SSE foam could effectively attenuate the external impact force and absorb the impact energy.Inherited from the excellent photothermal performance of MXene,M-SSE foam achieved a considerable saturated temperature of 98℃ under 0.57 W/cm^(2) laser power.Therefore,M-SSE foam showed extraordinary antimicrobial property for Staphylococcus aureus according to the principle of photothermal sterilization.Finally,for the development of intelligent wearable devices,conductive MSSE foam could be used as an intelligent sensor to monitor various human movements owing to the highly sensitive property.This work greatly expanded the application prospect of multifunctional protective materials in various complex environments and promoted the development of multifunctional smart wearable devices in protection field.

磁性液体数值模拟研究进展

磁性液体(magnetic fluid)是一种力学性能受磁场调控的磁流变智能材料,在医学与工业生产中有广泛应用.近年来,随着计算机性能的发展,数值模拟日益成为研究磁性液体力学行为细观机理的重要方法.本文综述并评价了磁性液体理论与数值模拟领域的最新研究进展,介绍了磁性液体在剪切、挤压和阀模式3种工作模式下的力学模型,对磁性液体的现有模拟方法进行了总结,讨论了磁性液体数值模拟的研究现状,并展望了数值模拟的发展前景.磁性液体的数值模拟亟待开展以下三方面研究:(1)建立涵盖多种微观相互作用的精细理论模型,研究颗粒表面包覆、添加剂等非磁性成分对磁流变效应的影响;(2)将不同数值模拟方法相结合,建立磁性液体的多尺度模型,进一步提高模拟精度,利用机器学习协调不同尺度的数值模拟,压缩计算量,已成为一种可行思路;(3)将力学模型与电、磁学模型相结合,发展多尺度、多物理场耦合的数值模拟方法,模拟磁性液体其他物理性能.最终为高性能磁性液体的研制及其应用研究提供技术和理论支撑.

Recent progress on the magnetorheological plastomers

Different from the traditional magnetorheological(MR)fluids and elastomers,the magnetic particles in the plastic MR materials are not‘deadly’trapped in the polymer matrix;thus,the MR plastomers exhibit higher MR effects and lower sedimentation.The plastic MR materials have attracted increasing attention,and the relevant fundamental mechanisms and practical applications have been intensively studied due to their unique physical and mechanical properties.In this highlight,we have mainly reviewed the preparation and the rheological properties of the MR plastomers.The formation mechanism of the MR plastomers has also been briefly summarized.

Sonochemical synthesis and characterization of magnetic separable Fe_(3)O_(4)-TiO_(2)nanocomposites and their catalytic properties

A novel sonochemical method is described for the preparation of Fe_(3)O_(4)–TiO_(2)photocatalysts in which nanocrystalline titanium dioxide particles are directly coated onto a magnetic core.The Fe_(3)O_(4)nanoparticles were partially embedded in TiO_(2)agglomerates.TiO_(2)nanocrystallites were obtained by hydrolysis and condensation of titanium tetraisopropyl in the presence of ethanol and water under high-intensity ultrasound irradiation.This method is attractive since it eliminated the high-temperature heat treatment required in the conventional sol–gel method,which is important in transforming amorphous titanium dioxide into a photoactive crystalline phase.In comparison to other methods,the developed method is simple,mild,green and efficient.The magnetization hysteresis loop for Fe_(3)O_(4)–TiO_(2)nanocomposites indicates that the hybrid catalyst shows superparamagnetic characteristics at room temperature.Photocatalytic activity studies confirmed that the as-prepared nanocomposites have high photocatalytic ability toward the photodegradation of RhB solution.Furthermore,the photodecomposition rate decreases only slightly after six cycles of the photocatalysis experiment.Thus,these Fe_(3)O_(4)–TiO_(2)nanocomposites can be served as an effective and conveniently recyclable photocatalyst.

The dynamic compressive properties of magnetorheological plastomers: enhanced magnetic-induced stresses by non-magnetic particles

In this research, a series of hollow glass powder(HGP) reinforced magnetorheological plastomers(MRPs)were prepared to improve the impact resistance of the materials, and the dynamic compressive properties of MRPs under high strain rate were investigated by using a split Hopkinson pressure bar(SHPB)system equipped with a customized magnetic device. Experimental results showed the HGPs greatly enhanced the yield stresses of the MRPs. Especially, for MRPs with 9 vol.% carbonyl iron powders(CIPs), the magnetic-induced yield stress increased from 7.3 MPa to 17.1 MPa(134% increased) by adding 18 vol.%HGPs. The particle structures in MRPs were further simulated and the corresponding intergranular stress was calculated to study the enhancement effect of HGPs. The simulated results showed that more compact structures were formed with the excluded volume caused by secondary HGPs, so the yield stresses of the MRPs increased under a magnetic field. However, when the mass ratio of HGP to CIP was larger than 0.67, HGPs would hinder the formation of chain-like structures and reduce the magneto-mechanical properties. As a result, the replacing of CIPs by HGPs was proven to be an excellent strategy to improve the dynamic properties of MRPs.

Hard-magnetic liquid metal droplets with excellent magnetic field dependent mobility and elasticity

Magnetic liquid metal droplets(MLMDs)have been proven to be very important in many fields such as flexible electronics and soft robotics.Usually,soft magnetic particles such as nickel(Ni)and iron(Fe)are mixed or suspended into the liquid metal to obtain soft MLMDs(S-LMDs),which can be easily manipulated under the magnetic field due to the favorable deformability and flexibility.In addition,hard magnetic particles such as neodymium iron boron(Nd Fe B)with a high residual magnetization can also be dispersed into the liquid metal and the hard MLMDs(H-LMDs)become more compact due to the interaction between internal particles induced by remanence.This work reports a kind of H-LMDs with high surface tension,high flexibility and mechanical robustness,whose electrical conductivity and strength are better than the S-LMDs.Under the magnetic field,the H-LMDs have a faster response time(0.58 s)and a larger actuating velocity(4.45 cm/s)than the S-LMDs.Moreover,the H-LMDs show excellent magnetic controllability,good elasticity and favorable mobility,as demonstrated by magnetically actuated locomotion,bounce tests and rolling angle measurements.Finally,the droplets can be further applied in wheeldriven motors and micro-valve switches,which demonstrates their high application potential in robotic manipulation and microfluidic devices.

Biocompatible and breathable healthcare electronics with sensing performances and photothermal antibacterial effect for motion-detecting

With the booming development of smart wearable devices,flexible multifunctional composites with high sensitivity and well health therapy have evoked great interest for next-generation healthcare electronics.However,the weak biocompatibility,low breathability,and narrow sensing range greatly hinder the development of healthcare sensors.Herein,a porous,flexible and conductive MXene/Polydimethylsiloxane/Polydopamine/Polyurethane Sponge(MXene/PDMS/PDA/PU)nanocomposite is developed as a promising motion-detecting device with good flexibility,breathability,sensing performance,photothermal therapy and antibacterial activity.Benefiting from the porous structure and biocompatible surface,this multifunctional sensor is further fabricated into a diagnostic and therapeutic system for monitoring human body motion and performing hot therapy/antibacterial treatment in the application of sports injury site.Moreover,both the wireless smart insole and cushion are constructed to gait monitoring and sit position detecting.This multifunctional hybrid sponge not only demonstrates great potential for motion monitoring sensors but also exhibits wide potential in wearable medical assistive and therapeutic systems.