Wearable strain sensors based on flexible conductive polymer composites(FCPCs)have attracted great attention due to their applications in the fields of human–machine interaction,disease diagnostics,human motion detec...Wearable strain sensors based on flexible conductive polymer composites(FCPCs)have attracted great attention due to their applications in the fields of human–machine interaction,disease diagnostics,human motion detection,and soft robotic skin.In recent decades,FCPC‐based strain sensors with high stretchability and sensitivity,short response time,and excellent stability have been developed,which are expected to be more versatile and intelligent.Smart strain sensors are required to provide wearable comfort,such as breathability,selfcooling ability,and so forth.To adapt to the harsh environment,wearable strain sensors should also be highly adaptive to protect the skin and the sensor itself.In addition,portable power supply system,multisite sensing capability,and multifunctionality are crucial for the next generation of FCPC‐based strain sensor.展开更多
Tissue engineering scaffolds play a vital role in regenerative medicine.It not only provides a temporary 3-dimensional support during tissue repair,but also regulates the cell behavior,such as cell adhesion,proliferat...Tissue engineering scaffolds play a vital role in regenerative medicine.It not only provides a temporary 3-dimensional support during tissue repair,but also regulates the cell behavior,such as cell adhesion,proliferation and differentiation.In this review,we summarize the development and trends of functional scaffolding biomaterials including electrically conducting hydrogels and nanocomposites of hydroxyapatite(HA)and bioactive glasses(BGs)with various biodegradable polymers.Furthermore,the progress on the fabrication of biomimetic nanofibrous scaffolds from conducting polymers and composites of HA and BG via electrospinning,deposition and thermally induced phase separation is discussed.Moreover,bioactive molecules and surface properties of scaffolds are very important during tissue repair.Bioactive molecule-releasing scaffolds and antimicrobial surface coatings for biomedical implants and scaffolds are also reviewed.展开更多
The lossy nature of indium tin oxide(ITO) at epsilon-near-zero(ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprisin...The lossy nature of indium tin oxide(ITO) at epsilon-near-zero(ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprising two ITO discs and a high dielectric constant perovskite barium strontium titanate(BST) film. The ENZ wavelength in the accumulation and depletion layers of ITO discs is controlled by applying a single bias voltage. The coupling of magnetic dipole resonance with the ENZ wavelength inside the accumulation layer of ITO film causes total absorption of reflected light. The reflection amplitude can achieve ~84 d B or ~99.99% modulation depth in the operation wavelength of 820 nm at a bias voltage of-2.5 V. Moreover, the metasurface is insensitive to the polarization of the incident light due to the circular design of resonators and the symmetrical design of bias connections.展开更多
Carbon materials engineered electrically conductive cement concrete(ECCC)is typically prepared by directly adding carbon-based conductive filler into the cement matrix and then mixing cement with aggregates.With such ...Carbon materials engineered electrically conductive cement concrete(ECCC)is typically prepared by directly adding carbon-based conductive filler into the cement matrix and then mixing cement with aggregates.With such a strategy,ECCC possesses a high conductivity and strain/stress sensitivity and thus can be used for snow and ice melting,ohmic heating,cathodic protection system,electromagnetic shielding,structural health monitoring,and traffic detection.This paper aims to provide a systematic review on the development and applications of ECCC,especially the progress made in the past decade(from 2012 to 2022).The composition and manufacture of ECCC are first introduced.Then,the electrical performance of ECCC and its potential applications are reviewed.Finally,the remaining challenges for future work are discussed.展开更多
Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged nanostructures.However,metasurfaces typicall...Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged nanostructures.However,metasurfaces typically have static optical responses with fixed geometries of nanostructures,which poses challenges for implementing transition to technology by replacing conventional optical components.To solve this problem,liquid crystals(LCs)have been actively employed for designing tunable metasurfaces using their adjustable birefringent in real time.Here,we review recent studies on LCpowered tunable metasurfaces,which are categorized as wavefront tuning and spectral tuning.Compared to numerous reviews on tunable metasurfaces,this review intensively explores recent development of LC-integrated metasurfaces.At the end of this review,we briefly introduce the latest research trends on LC-powered metasurfaces and suggest further directions for improving LCs.We hope that this review will accelerate the development of new and innovative LC-powered devices.展开更多
Heat dissipation of electronic devices keeps as a tough issue for decades. As the most classical coolant in a convective heat transfer process, water has been widely adopted which however inherits with limited thermal...Heat dissipation of electronic devices keeps as a tough issue for decades. As the most classical coolant in a convective heat transfer process, water has been widely adopted which however inherits with limited thermal conductivity and relies heavily on mechanical pump. As an alternative, the room temperature liquid metal was increasingly emerging as an important coolant to realize much stronger enhanced heat transfer. However, its thermal capacity is somewhat lower than that of water, which may restrict the overall cooling performance. In addition, the high cost by taking too much amount of liquid metal into the device also turns out to be a big concern for practical purpose. Here, through combining the individual merits from both the liquid metal with high conductivity and water with large heat capacity, we proposed and demonstrated a new conceptual cooling de- vice that integrated hybrid coolants, radiator and annular channel together for chip thermal management. Particularly, the elec- trically induced actuation effect of liquid metal was introduced as the only flow driving strategy, which significantly simplified the whole system design. This enables the liquid metal sphere and its surrounding aqueous solution to be quickly accelerated to a large speed under only a very low electric voltage. Further experiments demonstrated that the cooling device could effective- ly maintain the temperature of a hotpot （3.15 W/cm2） below 55℃ with an extremely small power consumption rate （0.8 W）. Sev- eral situations to simulate the practical working of the device were experimentally explored and a theoretical thermal resistance model was established to evaluate its heat transfer performance. The present work suggests an important way to make highly compact chip cooling device, which can be flexibly extended into a wide variety of engineering areas.展开更多
We investigated the electric controllable spin-filtering effect in a zigzag phosphorene nanoribbon(ZPNR) based normal–antiferromagnet–normal junction. Two ferromagnets are closely coupled to the edges of the nanorib...We investigated the electric controllable spin-filtering effect in a zigzag phosphorene nanoribbon(ZPNR) based normal–antiferromagnet–normal junction. Two ferromagnets are closely coupled to the edges of the nanoribbon and form the edge-to-edge antiferromagnetism. Under an in-plane electric field, the two degenerate edge bands of the edge-to-edge antiferromagnet split into four spin-polarized sub-bands and a 100% spin-polarized current can be easily induced with the maximal conductance 2e~2/h. The spin polarization changes with the strength of the electric field and the exchange field,and changes sign at opposite electric fields. The spin-polarized current switches from one edge to the other by reversing the direction of the electric field. The edge current can also be controlled spatially by changing the electric potential of the scattering region. The manipulation of edge current is useful in spin-transfer-torque magnetic random-access memory and provides a practical way to develop controllable spintronic devices.展开更多
Leakage currents accelerate surface degradation of metal contacts via small scale arcing across lubricating films,but recent observations suggest that metallic nanoparticle additives in lubricants may be useful to imp...Leakage currents accelerate surface degradation of metal contacts via small scale arcing across lubricating films,but recent observations suggest that metallic nanoparticle additives in lubricants may be useful to improve contact performance.These findings prompted a study that examined electrically induced surface pitting of steel contacts in the presence of several lubricating greases including some containing nanometer-sized colloidal silver(Ag)particles.Reciprocating rolling sphere-on-disk experiments were conducted under electro-tribological loads employing polyurea greases derived from mineral and synthetic base oils with and without additives.Friction forces and electrical resistance were monitored continuously during the tests;surface changes were characterized by means of optical spectroscopy,stylus profilometry,and scanning electron microscopy(SEM)including compositional analysis using energy dispersive spectroscopy(EDS).The observations demonstrate that surface pitting induced by arcing occurs mainly at the points were the rolling motion changes direction and that eroded metal is deposited along the wear grove.Micron-sized pits are formed which contain carbon and oxygen indicating that arcing causes decomposition of the hydrocarbon lubricants.Numerous findings indicate a significant inhibition of pitting is induced by the Ag nanoparticles;some greases containing other additives exhibit a similar,although less pronounced,effect.展开更多
Given that graphene features high electrical conductivity,it is a kind of material with corrosion-promotion activity.This study aimed to inhibit the corrosion-promotion activity of graphene in coatings.Here,we report ...Given that graphene features high electrical conductivity,it is a kind of material with corrosion-promotion activity.This study aimed to inhibit the corrosion-promotion activity of graphene in coatings.Here,we report an exciting application of epoxy matrix(EP)/F-doped reduced graphene oxide(rGO)coatings for the long-term corrosion protection of steel.The synthesized F-doped rGO(FG)did not reduce the utilization of rGO by a wide margin and possessed distinctive electrically insulating nature.The electrical conductivity of rGO was approximately 1500 S/m,whereas those of FG-1,FG-2 and FG-3 were 1.17,5.217×10^−2 and 3.643×10^-11 S/m,respectively.FG and rGO were then dispersed into epoxy coatings.The chemical structures of rGO and FG were investigated by transmission electron microscopy(TEM),scanning probe microscopy(SPM),X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD).EP/FG coatings exhibited outstanding corrosion protection in comparison with blank EP and EP/rGO coatings mainly because the corrosion-promotion effect of rGO was eliminated.The anticorrosion ability of EP/FG coatingswasimproved with increased F-doped degree of FG.In addition,electrochemical impendance spectroscopy(EIS)results indicated that the Rc values of EP/FG-2 and EP/FG-3 were four orders of magnitude higher than those of EP/rGO in diluent NaCl solution(3.5 wt.%)after immersion for 90 days.展开更多
The article presents an experimental study on the flow of an eutectic gallium alloy in a cylindrical cell,which is placed in an alternating magnetic field.The magnetic field is generated by a coil connected to an alte...The article presents an experimental study on the flow of an eutectic gallium alloy in a cylindrical cell,which is placed in an alternating magnetic field.The magnetic field is generated by a coil connected to an alternating current source.The coil is located at a fixed height in such a way that its plane is perpendicular to the gravity vector,which in turn is parallel to the axis of the cylinder.The position of the cylinder can vary in height with respect to the coil.The forced flow of the considered electrically conductive liquid is generated due to the action of the localized electromagnetic force.It is assumed that under the action of the alternating magnetic field,the liquid is heated uniformly,and the resulting heat is quickly absorbed by the forced flow,so that liquid free convection can be neglected.The experiment is carried out using an ultrasonic Doppler anemometer.One transducer is installed in the axially located cylinder sluice and the other transducer is placed in the near-wall region.According to the results,a velocity profile,corresponding to a two-tori flow pattern can be hardly obtained in the low frequency range of the power supply.However,this is possible in the high frequency range.The average velocity profiles depend essentially on the location of the coil relative to the cell.The spectral analysis of velocity signals shows that the amplitude of the velocity pulsations is comparable to the average value of the flow velocity.Such experimental results and their verification through comparison with numerical calculations are intended to support the development of new methods for reducing the intensity of vortex flows during the electromagnetic separation of impurities through an electromagnetic induction mechanism(able to produce an electromotive force that displaces particles).展开更多
The deicing experiment of carbon fiber reinforced electrically conductive concrete （CFRC） slab was conducted in laboratory at first, then the deicing process of CFRC parement was analyzed by means of finite elemen...The deicing experiment of carbon fiber reinforced electrically conductive concrete （CFRC） slab was conducted in laboratory at first, then the deicing process of CFRC parement was analyzed by means of finite element method （FEM）. At last, based on the energy conservation law and the computing restdts of finite element method, the influential factors including the setting of electric heating layer, environmental temperature, the thickness of ice, material parameters, and deicing power on deicing performance and energy consumption were discussed.展开更多
Design of rapidly detachable adhesives with high initial bonding strength is of great significance but it is full of great challenge. Here, we report the fast electrically detaching behavior (100% detaching efficiency...Design of rapidly detachable adhesives with high initial bonding strength is of great significance but it is full of great challenge. Here, we report the fast electrically detaching behavior (100% detaching efficiency in just 1 min under dozens of DC voltage) and high initial bonding strength (>12 MPa) of epoxy-based ionic conductive adhesives (ICAs). The epoxy-based ICAs are fabricated by introducing polyethylene glycol dimethyl ether (PEGDE) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM]OTF) into epoxy. The combination of PEGDE and [EMIM]OTF enables the free ions to migrate directively in electric field, and the anchoring of PEG chains onto epoxy chains ensures the long-term reliability of ICAs. The investigation on the electrically detaching mechanism suggests that the enrichment and following rapid interfacial electrochemical reactions of [EMIM]OTF lead to formation of metal hydroxide (Me(OH)n) nanoparticles at the bonding interfaces, thus the strong interactions containing interlocked forces, van de Waals’ forces and hydrogen bonding interactions between ICAs and bonding substrates are destroyed. This work provides a promising direction for detachable adhesives with both high initial bonding strength and high detaching efficiency in short time.展开更多
A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styren...A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styrene/Cu （ABS/Cu） gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 10^15 Ω at ABS rich side, while that declined to 10^5 Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vo1%- 4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.展开更多
Carbon fiber reinforced concrete (CFRC) is a kind of good electrothermal material. When connected to an external power supply, stable and uniform heat suitable for deicing application is generated in the CFRC slab. El...Carbon fiber reinforced concrete (CFRC) is a kind of good electrothermal material. When connected to an external power supply, stable and uniform heat suitable for deicing application is generated in the CFRC slab. Electric heating and deicing experiments of carbon fiber reinforced concrete slab were carried out in laboratory, and the effect of the temperature and thickness of ice, the thermal conductivity of CFRC, and power output on deicing performance and energy consumption were investigated. The experimental results indicate that it is an effective method to utilize the thermal energy produced by CFRC slab to deice. The time to melt the ice completely decreases with increasing power output and ice temperature, and increases with increasing thickness of the ice. The energy consumption to melt 2 mm thickness of ice varies approximately linearly from 0.556 to 0.846 kW·h/m2 as the initial temperature ranges from -3℃ to - 18℃. CFRC with good thermal conduction can reduce temperature difference in CFRC slab effectively.展开更多
Electrically controlled rotor （ECR） system has the potential to enhance the rotor perfor- mance by applying higher harmonic flap inputs. In order to explore the feasibility and effectiveness for ECR performance enha...Electrically controlled rotor （ECR） system has the potential to enhance the rotor perfor- mance by applying higher harmonic flap inputs. In order to explore the feasibility and effectiveness for ECR performance enhancement using closed-loop control method, firstly, an ECR rotor performance analysis model based on helicopter flight dynamic model is established, which can reflect the performance characteristics of ECR helicopter at high advance ratio. Based on the simulation platform, an active control method named adaptive T-matrix algorithm is adopted to explore the feasibility and effectiveness for ECR performance enhancement. The simulation results verify the effectiveness of this closed-loop control method. For the sample ECR helicopter, about 3% rotor power reduction is obtained with the optimum 2/rev flap inputs at the advance ratio of 0.34. And through analyzing the distributions of attack of angle and drag in rotor disk, the underlying physical essence of ECR power reduction is cleared. Furthermore, the influence of the key control parameters, including convergence factor and weighting matrix, on the effectiveness of closed-loop control for ECR performance enhancement is explored. Some useful results are summarized, which can be used to direct the future active control law design of ECR performance enhancement.展开更多
Materials such as Koch AH-70,basalt aggregate,limestone powder and graphite particles were used to prepare conductive asphalt concrete,which is a new type of multifunctional concrete.The mix proportion by weight was s...Materials such as Koch AH-70,basalt aggregate,limestone powder and graphite particles were used to prepare conductive asphalt concrete,which is a new type of multifunctional concrete.The mix proportion by weight was shown as follows.Fine aggregates (2.36-4.75 mm)∶fine aggregates (<2.36mm)∶limestone powder∶asphalt=120∶240∶14∶30.The content of added graphite particles ranged from 0% to 20%(by the weight of asphalt concrete).A conductive asphalt concrete with a resistivity around 10-10 3Ω·m was obtained.Special attention was paid to the effects of graphite content,graphite physical-chemical properties,asphalt content and temperature on the resistivity.Furthermore,an attempt was made to develop an electrically conductive model for asphalt concrete.展开更多
The electrically driven large-load-ratio six-legged robot with engineering capability can be widely used in outdoor and planetary exploration.However,due to the particularity of its parallel structure,the effective ut...The electrically driven large-load-ratio six-legged robot with engineering capability can be widely used in outdoor and planetary exploration.However,due to the particularity of its parallel structure,the effective utilization rate of energy is not high,which has become an important obstacle to its practical application.To research the power consumption characteristics of robot mobile system is beneficial to speed up it toward practicability.Based on the configuration and walking modes of robot,the mathematical model of the power consumption of mobile system is set up.In view of the tripod gait is often selected for the six-legged robots,the simplified power consumption model of mobile system under the tripod gait is established by means of reducing the dimension of the robot’s statically indeterminate problem and constructing the equal force distribution.Then,the power consumption of robot mobile system is solved under different working conditions.The variable tendencies of the power consumption of robot mobile system are respectively obtained with changes in the rotational angles of hip joint and knee joint,body height,and span.The articulated rotational zones and the ranges of body height and span are determined under the lowest power consumption.According to the walking experiments of prototype,the variable tendencies of the average power consumption of robot mobile system are respectively acquired with changes in duty ratio,body height,and span.Then,the feasibility and correctness of theory analysis are verified in the power consumption of robot mobile system.The proposed analysis method in this paper can provide a reference on the lower power research of the large-load-ratio multi-legged robots.展开更多
This study has been conducted to evaluate the application of silver nanoparticles(NPs)in Electrically Conductive Adhesives(ECAs),filled with hybrid silver flakes and NPs,and silver flakes as a control sample,at a fill...This study has been conducted to evaluate the application of silver nanoparticles(NPs)in Electrically Conductive Adhesives(ECAs),filled with hybrid silver flakes and NPs,and silver flakes as a control sample,at a filler loading of 78 wt.%,83 wt.%and 88 wt.%and cured at 150℃and 180℃,respectively.The results show that the electrical and thermal conductivities of ECAs were improved with the increasing of filler loading and curing temperature.Adding silver NPs in silver flakes negatively affected the electrical and thermal conductivities of ECAs at a low filler mass fraction of 78 wt.%,because the segregation of NPs enlarged the average distance of silver flakes;while it positively influenced the electrical and thermal conductivities of ECAs at a loading ratio of 88 wt.%,probably due to NPs filling in the gaps between silver flakes or even sintering together with each other or with silver flakes,especially when curing at high temperature of 180℃.展开更多
基金Henan Province University Innovation Talents Support Program,Grant/Award Number:20HASTIT001National Natural Science Foundation of China,Grant/Award Numbers:51773183,U1604253,U1804133Innovation Team of Colleges and Universities in Henan Province,Grant/Award Number:20IRTSTHN002。
文摘Wearable strain sensors based on flexible conductive polymer composites(FCPCs)have attracted great attention due to their applications in the fields of human–machine interaction,disease diagnostics,human motion detection,and soft robotic skin.In recent decades,FCPC‐based strain sensors with high stretchability and sensitivity,short response time,and excellent stability have been developed,which are expected to be more versatile and intelligent.Smart strain sensors are required to provide wearable comfort,such as breathability,selfcooling ability,and so forth.To adapt to the harsh environment,wearable strain sensors should also be highly adaptive to protect the skin and the sensor itself.In addition,portable power supply system,multisite sensing capability,and multifunctionality are crucial for the next generation of FCPC‐based strain sensor.
基金The authors gratefully acknowledge the financial support of the US National Institutes of Health(NIDCR DE015384,DE017689,DE022327),DOD(W81XWH-12-2-0008)the National Science Foundation of the United States(DMR-1206575)the National Natural Science Foundation of China(21304073 and 51403173).
文摘Tissue engineering scaffolds play a vital role in regenerative medicine.It not only provides a temporary 3-dimensional support during tissue repair,but also regulates the cell behavior,such as cell adhesion,proliferation and differentiation.In this review,we summarize the development and trends of functional scaffolding biomaterials including electrically conducting hydrogels and nanocomposites of hydroxyapatite(HA)and bioactive glasses(BGs)with various biodegradable polymers.Furthermore,the progress on the fabrication of biomimetic nanofibrous scaffolds from conducting polymers and composites of HA and BG via electrospinning,deposition and thermally induced phase separation is discussed.Moreover,bioactive molecules and surface properties of scaffolds are very important during tissue repair.Bioactive molecule-releasing scaffolds and antimicrobial surface coatings for biomedical implants and scaffolds are also reviewed.
基金supported by the Agency for Science, Technology and Research (A*STAR) under AME IRG Grant No. A2083c0058AME IAF-PP Grant No. 182 24 30030+1 种基金HBMS IAF-PP Grant No. H19H6a0025by MOE Tier 3 program LUNI170919a PUBMOE。
文摘The lossy nature of indium tin oxide(ITO) at epsilon-near-zero(ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprising two ITO discs and a high dielectric constant perovskite barium strontium titanate(BST) film. The ENZ wavelength in the accumulation and depletion layers of ITO discs is controlled by applying a single bias voltage. The coupling of magnetic dipole resonance with the ENZ wavelength inside the accumulation layer of ITO film causes total absorption of reflected light. The reflection amplitude can achieve ~84 d B or ~99.99% modulation depth in the operation wavelength of 820 nm at a bias voltage of-2.5 V. Moreover, the metasurface is insensitive to the polarization of the incident light due to the circular design of resonators and the symmetrical design of bias connections.
基金The authors would like to acknowledge the financial support by the National Natural Science Foundation of China(Grant Nos.52278164 and 51878224)the National Key Research and Development Program of China(Gant No.2022YFB3706503).
文摘Carbon materials engineered electrically conductive cement concrete(ECCC)is typically prepared by directly adding carbon-based conductive filler into the cement matrix and then mixing cement with aggregates.With such a strategy,ECCC possesses a high conductivity and strain/stress sensitivity and thus can be used for snow and ice melting,ohmic heating,cathodic protection system,electromagnetic shielding,structural health monitoring,and traffic detection.This paper aims to provide a systematic review on the development and applications of ECCC,especially the progress made in the past decade(from 2012 to 2022).The composition and manufacture of ECCC are first introduced.Then,the electrical performance of ECCC and its potential applications are reviewed.Finally,the remaining challenges for future work are discussed.
基金supported by the POSCO-POSTECH-RIST Convergence Research Center program funded by POSCO,the Samsung Research Funding&Incubation Center for Future Technology grant(SRFC-IT1901-52)funded by Samsung Electronicsthe National Research Foundation(NRF)grants(NRF-2022M3C1A3081312,NRF-2022M3H4A1A-02074314,NRF-2022M3H4A1A02046445,NRF-2021M3H4A1A04086357,NRF-2019R1A5A8080290,RS-2024-00356928,RS-2023-00283667)funded by the Ministry of Science and ICT of the Korean governmentthe Korea Evaluation Institute of Industrial Technology(KEIT)grant(No.1415185027/20019169,Alchemist project)funded by the Ministry of Trade,Industry and Energy(MOTIE)of the Korean government.H.Kim and J.Kim acknowledge the POSTECH Alchemist fellowship,the Asan Foundation Biomedical Science fellowship,and Presidential Science fellowship funded by the MSIT of the Korean government.
文摘Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged nanostructures.However,metasurfaces typically have static optical responses with fixed geometries of nanostructures,which poses challenges for implementing transition to technology by replacing conventional optical components.To solve this problem,liquid crystals(LCs)have been actively employed for designing tunable metasurfaces using their adjustable birefringent in real time.Here,we review recent studies on LCpowered tunable metasurfaces,which are categorized as wavefront tuning and spectral tuning.Compared to numerous reviews on tunable metasurfaces,this review intensively explores recent development of LC-integrated metasurfaces.At the end of this review,we briefly introduce the latest research trends on LC-powered metasurfaces and suggest further directions for improving LCs.We hope that this review will accelerate the development of new and innovative LC-powered devices.
基金supported by the Research Funding from the Technical Institute of Physics and ChemistryChinese Academy of Sciences
文摘Heat dissipation of electronic devices keeps as a tough issue for decades. As the most classical coolant in a convective heat transfer process, water has been widely adopted which however inherits with limited thermal conductivity and relies heavily on mechanical pump. As an alternative, the room temperature liquid metal was increasingly emerging as an important coolant to realize much stronger enhanced heat transfer. However, its thermal capacity is somewhat lower than that of water, which may restrict the overall cooling performance. In addition, the high cost by taking too much amount of liquid metal into the device also turns out to be a big concern for practical purpose. Here, through combining the individual merits from both the liquid metal with high conductivity and water with large heat capacity, we proposed and demonstrated a new conceptual cooling de- vice that integrated hybrid coolants, radiator and annular channel together for chip thermal management. Particularly, the elec- trically induced actuation effect of liquid metal was introduced as the only flow driving strategy, which significantly simplified the whole system design. This enables the liquid metal sphere and its surrounding aqueous solution to be quickly accelerated to a large speed under only a very low electric voltage. Further experiments demonstrated that the cooling device could effective- ly maintain the temperature of a hotpot （3.15 W/cm2） below 55℃ with an extremely small power consumption rate （0.8 W）. Sev- eral situations to simulate the practical working of the device were experimentally explored and a theoretical thermal resistance model was established to evaluate its heat transfer performance. The present work suggests an important way to make highly compact chip cooling device, which can be flexibly extended into a wide variety of engineering areas.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.12174077 and 12174051)the Science Foundation of GuangDong Province (Grant No.2021A1515012363)GuangDong Basic and Applied Basic Research Foundation (Grant No.2022A1515110011)。
文摘We investigated the electric controllable spin-filtering effect in a zigzag phosphorene nanoribbon(ZPNR) based normal–antiferromagnet–normal junction. Two ferromagnets are closely coupled to the edges of the nanoribbon and form the edge-to-edge antiferromagnetism. Under an in-plane electric field, the two degenerate edge bands of the edge-to-edge antiferromagnet split into four spin-polarized sub-bands and a 100% spin-polarized current can be easily induced with the maximal conductance 2e~2/h. The spin polarization changes with the strength of the electric field and the exchange field,and changes sign at opposite electric fields. The spin-polarized current switches from one edge to the other by reversing the direction of the electric field. The edge current can also be controlled spatially by changing the electric potential of the scattering region. The manipulation of edge current is useful in spin-transfer-torque magnetic random-access memory and provides a practical way to develop controllable spintronic devices.
文摘Leakage currents accelerate surface degradation of metal contacts via small scale arcing across lubricating films,but recent observations suggest that metallic nanoparticle additives in lubricants may be useful to improve contact performance.These findings prompted a study that examined electrically induced surface pitting of steel contacts in the presence of several lubricating greases including some containing nanometer-sized colloidal silver(Ag)particles.Reciprocating rolling sphere-on-disk experiments were conducted under electro-tribological loads employing polyurea greases derived from mineral and synthetic base oils with and without additives.Friction forces and electrical resistance were monitored continuously during the tests;surface changes were characterized by means of optical spectroscopy,stylus profilometry,and scanning electron microscopy(SEM)including compositional analysis using energy dispersive spectroscopy(EDS).The observations demonstrate that surface pitting induced by arcing occurs mainly at the points were the rolling motion changes direction and that eroded metal is deposited along the wear grove.Micron-sized pits are formed which contain carbon and oxygen indicating that arcing causes decomposition of the hydrocarbon lubricants.Numerous findings indicate a significant inhibition of pitting is induced by the Ag nanoparticles;some greases containing other additives exhibit a similar,although less pronounced,effect.
基金This work was financially supported by the National Natural Science Foundation of China(No.51775540)the Youth Innovation Promotion Association,CAS(No.2017338)+1 种基金the Nature Science Foundation of Zhejiang(No.LQ19E030007)the Natural Science Foundation of Ningbo(No.2018A610114).
文摘Given that graphene features high electrical conductivity,it is a kind of material with corrosion-promotion activity.This study aimed to inhibit the corrosion-promotion activity of graphene in coatings.Here,we report an exciting application of epoxy matrix(EP)/F-doped reduced graphene oxide(rGO)coatings for the long-term corrosion protection of steel.The synthesized F-doped rGO(FG)did not reduce the utilization of rGO by a wide margin and possessed distinctive electrically insulating nature.The electrical conductivity of rGO was approximately 1500 S/m,whereas those of FG-1,FG-2 and FG-3 were 1.17,5.217×10^−2 and 3.643×10^-11 S/m,respectively.FG and rGO were then dispersed into epoxy coatings.The chemical structures of rGO and FG were investigated by transmission electron microscopy(TEM),scanning probe microscopy(SPM),X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD).EP/FG coatings exhibited outstanding corrosion protection in comparison with blank EP and EP/rGO coatings mainly because the corrosion-promotion effect of rGO was eliminated.The anticorrosion ability of EP/FG coatingswasimproved with increased F-doped degree of FG.In addition,electrochemical impendance spectroscopy(EIS)results indicated that the Rc values of EP/FG-2 and EP/FG-3 were four orders of magnitude higher than those of EP/rGO in diluent NaCl solution(3.5 wt.%)after immersion for 90 days.
基金supported by Russian Science Foundation Grant RSF-22-19-20106。
文摘The article presents an experimental study on the flow of an eutectic gallium alloy in a cylindrical cell,which is placed in an alternating magnetic field.The magnetic field is generated by a coil connected to an alternating current source.The coil is located at a fixed height in such a way that its plane is perpendicular to the gravity vector,which in turn is parallel to the axis of the cylinder.The position of the cylinder can vary in height with respect to the coil.The forced flow of the considered electrically conductive liquid is generated due to the action of the localized electromagnetic force.It is assumed that under the action of the alternating magnetic field,the liquid is heated uniformly,and the resulting heat is quickly absorbed by the forced flow,so that liquid free convection can be neglected.The experiment is carried out using an ultrasonic Doppler anemometer.One transducer is installed in the axially located cylinder sluice and the other transducer is placed in the near-wall region.According to the results,a velocity profile,corresponding to a two-tori flow pattern can be hardly obtained in the low frequency range of the power supply.However,this is possible in the high frequency range.The average velocity profiles depend essentially on the location of the coil relative to the cell.The spectral analysis of velocity signals shows that the amplitude of the velocity pulsations is comparable to the average value of the flow velocity.Such experimental results and their verification through comparison with numerical calculations are intended to support the development of new methods for reducing the intensity of vortex flows during the electromagnetic separation of impurities through an electromagnetic induction mechanism(able to produce an electromotive force that displaces particles).
文摘The deicing experiment of carbon fiber reinforced electrically conductive concrete （CFRC） slab was conducted in laboratory at first, then the deicing process of CFRC parement was analyzed by means of finite element method （FEM）. At last, based on the energy conservation law and the computing restdts of finite element method, the influential factors including the setting of electric heating layer, environmental temperature, the thickness of ice, material parameters, and deicing power on deicing performance and energy consumption were discussed.
基金supported by the National Natural Science Foundation of China (No. 52103097)the Doctor Foundation of Southwest University of Science and Technology (No. 20zx7144)+3 种基金the Special Foundation for Young Scientists of Sichuan Province (No. 71112541)the Guangdong Natural Science Foundation (No. 2021A1515010675)the Key Project of Guangzhou Science and Technology Plan Project (No. 201904020034)the Guangdong Project of R&D Plan in Key Areas (No. 2020B010180001).
文摘Design of rapidly detachable adhesives with high initial bonding strength is of great significance but it is full of great challenge. Here, we report the fast electrically detaching behavior (100% detaching efficiency in just 1 min under dozens of DC voltage) and high initial bonding strength (>12 MPa) of epoxy-based ionic conductive adhesives (ICAs). The epoxy-based ICAs are fabricated by introducing polyethylene glycol dimethyl ether (PEGDE) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM]OTF) into epoxy. The combination of PEGDE and [EMIM]OTF enables the free ions to migrate directively in electric field, and the anchoring of PEG chains onto epoxy chains ensures the long-term reliability of ICAs. The investigation on the electrically detaching mechanism suggests that the enrichment and following rapid interfacial electrochemical reactions of [EMIM]OTF lead to formation of metal hydroxide (Me(OH)n) nanoparticles at the bonding interfaces, thus the strong interactions containing interlocked forces, van de Waals’ forces and hydrogen bonding interactions between ICAs and bonding substrates are destroyed. This work provides a promising direction for detachable adhesives with both high initial bonding strength and high detaching efficiency in short time.
基金Funded by the National Natural Science Foundation of China(No.21274007)the Beijing Natural Science Foundation+1 种基金the Key Scientific Project of Beijing Municipal Education Commission(No.KZ201110011014)the Science and Technology Innovation Platform of Beijing Municipal Education Commission(No.PXM2012-014213-000025)
文摘A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styrene/Cu （ABS/Cu） gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 10^15 Ω at ABS rich side, while that declined to 10^5 Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vo1%- 4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.
基金This work was supported by the key project of National Natural Science Foundation of China under grant No.50238040.
文摘Carbon fiber reinforced concrete (CFRC) is a kind of good electrothermal material. When connected to an external power supply, stable and uniform heat suitable for deicing application is generated in the CFRC slab. Electric heating and deicing experiments of carbon fiber reinforced concrete slab were carried out in laboratory, and the effect of the temperature and thickness of ice, the thermal conductivity of CFRC, and power output on deicing performance and energy consumption were investigated. The experimental results indicate that it is an effective method to utilize the thermal energy produced by CFRC slab to deice. The time to melt the ice completely decreases with increasing power output and ice temperature, and increases with increasing thickness of the ice. The energy consumption to melt 2 mm thickness of ice varies approximately linearly from 0.556 to 0.846 kW·h/m2 as the initial temperature ranges from -3℃ to - 18℃. CFRC with good thermal conduction can reduce temperature difference in CFRC slab effectively.
基金supported by the National Natural Science Foundation of China (No. 51375229)
文摘Electrically controlled rotor （ECR） system has the potential to enhance the rotor perfor- mance by applying higher harmonic flap inputs. In order to explore the feasibility and effectiveness for ECR performance enhancement using closed-loop control method, firstly, an ECR rotor performance analysis model based on helicopter flight dynamic model is established, which can reflect the performance characteristics of ECR helicopter at high advance ratio. Based on the simulation platform, an active control method named adaptive T-matrix algorithm is adopted to explore the feasibility and effectiveness for ECR performance enhancement. The simulation results verify the effectiveness of this closed-loop control method. For the sample ECR helicopter, about 3% rotor power reduction is obtained with the optimum 2/rev flap inputs at the advance ratio of 0.34. And through analyzing the distributions of attack of angle and drag in rotor disk, the underlying physical essence of ECR power reduction is cleared. Furthermore, the influence of the key control parameters, including convergence factor and weighting matrix, on the effectiveness of closed-loop control for ECR performance enhancement is explored. Some useful results are summarized, which can be used to direct the future active control law design of ECR performance enhancement.
文摘Materials such as Koch AH-70,basalt aggregate,limestone powder and graphite particles were used to prepare conductive asphalt concrete,which is a new type of multifunctional concrete.The mix proportion by weight was shown as follows.Fine aggregates (2.36-4.75 mm)∶fine aggregates (<2.36mm)∶limestone powder∶asphalt=120∶240∶14∶30.The content of added graphite particles ranged from 0% to 20%(by the weight of asphalt concrete).A conductive asphalt concrete with a resistivity around 10-10 3Ω·m was obtained.Special attention was paid to the effects of graphite content,graphite physical-chemical properties,asphalt content and temperature on the resistivity.Furthermore,an attempt was made to develop an electrically conductive model for asphalt concrete.
基金National Natural Science Foundation of China(Grant No.51505335)Industry University Cooperation Collaborative Education Project of the Department of Higher Education of the Ministry of Education of China(Grant No.202102517001)Doctor Startup Projects of TUTE of China(Grant No.KYQD1806)。
文摘The electrically driven large-load-ratio six-legged robot with engineering capability can be widely used in outdoor and planetary exploration.However,due to the particularity of its parallel structure,the effective utilization rate of energy is not high,which has become an important obstacle to its practical application.To research the power consumption characteristics of robot mobile system is beneficial to speed up it toward practicability.Based on the configuration and walking modes of robot,the mathematical model of the power consumption of mobile system is set up.In view of the tripod gait is often selected for the six-legged robots,the simplified power consumption model of mobile system under the tripod gait is established by means of reducing the dimension of the robot’s statically indeterminate problem and constructing the equal force distribution.Then,the power consumption of robot mobile system is solved under different working conditions.The variable tendencies of the power consumption of robot mobile system are respectively obtained with changes in the rotational angles of hip joint and knee joint,body height,and span.The articulated rotational zones and the ranges of body height and span are determined under the lowest power consumption.According to the walking experiments of prototype,the variable tendencies of the average power consumption of robot mobile system are respectively acquired with changes in duty ratio,body height,and span.Then,the feasibility and correctness of theory analysis are verified in the power consumption of robot mobile system.The proposed analysis method in this paper can provide a reference on the lower power research of the large-load-ratio multi-legged robots.
基金Project was supported by the Natural Science Foundation of Guangdong Province(No.2019A1515011844)the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory(ZHD201801 and 31512050201).
文摘This study has been conducted to evaluate the application of silver nanoparticles(NPs)in Electrically Conductive Adhesives(ECAs),filled with hybrid silver flakes and NPs,and silver flakes as a control sample,at a filler loading of 78 wt.%,83 wt.%and 88 wt.%and cured at 150℃and 180℃,respectively.The results show that the electrical and thermal conductivities of ECAs were improved with the increasing of filler loading and curing temperature.Adding silver NPs in silver flakes negatively affected the electrical and thermal conductivities of ECAs at a low filler mass fraction of 78 wt.%,because the segregation of NPs enlarged the average distance of silver flakes;while it positively influenced the electrical and thermal conductivities of ECAs at a loading ratio of 88 wt.%,probably due to NPs filling in the gaps between silver flakes or even sintering together with each other or with silver flakes,especially when curing at high temperature of 180℃.
