A critical review of carbon materials engineered electrically conductive cement concrete and its potential applications

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.

A bio-inspired 3D metamaterials with chirality and anti-chirality topology fabricated by 4D printing

Artificial architected metamaterials equipped with unique mechanical and physical properties that are naturally inaccessible can be obtained by rational design.In this work,the innovative three-dimensional(3D)chiral and anti-chiral metamaterials are developed referring to the face-rotating polyhedral(FRP)structure present in the virus.Through assembling planar triangular units into the regular octahedron cells,several typical forms of chiral and anti-chiral metamaterials can be obtained by different assembly methods.By changing the topology parameters,the Poisson’s ratio can be adjusted between[0,2.8].The metamaterials are fabricated by 3D printing utilizing shape memory polymer,and the mechanical properties are analyzed via Finite Element Analysis(FEA)and experiments,including Young’s modulus,Poisson’s ratio,and tension-twist coupling behavior.In addition,target metamaterial with specific local deformation behavior is obtained by programmatic calculations and distributions to meet special requirements or achieve unique applications.The shape memory property endows the mechanical metamaterials with more potential applications.

Integrating reduced graphene oxides and PPy nanoparticles for enhanced electricity from water evaporation

Developing high-performance nanostructured materials is key to deliver the potential of hydrovoltaic technology into practical applications.As single-component materials have approached its limit in generating hydrovoltaic electricity,the development of multi-component hydrovoltaic materials has been necessary in continuously boosting the electricity output.Here,we report a hydrovoltaic material by integrating reduced graphene oxides and polypyrrole nanoparticles(rGO/PPy),where the rGO contributes improved conductivity and large specific surface area while PPy nanoparticles enable enhanced interaction with water.The device fabricated with this material generates a short-circuit current of 6μA as well as a maximum power density of over 1μW/cm3 from natural evaporation of water.And the substantial ion-PPy interaction enables robust voltage generation from evaporation of various salt solutions.Moreover,an outstanding scaling ability is demonstrated by connecting 10 devices in series that generate a sustainable voltage of up to~2.5 V,sufficing to power many commercial devices,e.g.LED bulb and LCD screen.

Failure mechanisms in flexible electronics

The rapid evolution of flexible electronic devices promises to revolutionize numerous fields by expanding the applications of smart devices.Nevertheless,despite this vast potential,the reliability of these innovative devices currently falls short,especially in light of demanding operation environment and the intrinsic challenges associated with their fabrication techniques.The heterogeneity in these processes and environments gives rise to unique failure modes throughout the devices'lifespan.To significantly enhance the reliability of these devices and assure long-term performance,it is paramount to comprehend the underpinning failure mechanisms thoroughly,thereby,enabling,optimal design solutions.A myriad of investigative efforts have been dedicated to unravel these failure mechanisms,utilizing a spectrum of tools from analytical models,numerical methods,to advanced characterization methods.This review delves into the root causes of device failure,scrutinizing both the fabrication process and the operation environment.Next,We subsequently address the failure mechanisms across four commonly observed modes:strength failure,fatigue failure,interfacial failure,and electrical failure,followed by an overview of targeted characterization methods associated with each mechanism.Concluding with an outlook,we spotlight ongoing challenges and promising directions for future research in our pursuit of highly resilient flexible electronic devices.

Instant formation of nanopores on flexible polymer membranes using intense pulsed light and nanoparticle templates

The development of simple and high-throughput approaches to yield solid-state nanopores on large surface membranes may facilitate the prevalence of nanopore analysis technology and in-vitro diagnosis using portable devices.However,solidstate nanopores are typically realized by complex and highend nanofabrication equipments.Here,we present a method to achieve nanopores on polymer membranes using,silver nanoparticles(AgNPs)as templates and intense pulsed light(IPL)as a heating source.The density and size of nanopores are controllable by adjusting the spin coating rate,the concentration of nanoparticle suspension,and the size of nanoparticles(NPs).The temperature of the AgNPs can rapidly reach 1132 K under instant heating of photothermal effect through light irradiation in 2 ms,resulting in localized melting and decomposition of an underneath polycarbonate(PC)membrane to yield nanopores with sizes ranging from 10 to 270 nm.After removing the nanoparticle residues,the flexible membrane with nanopores can be integrated into a flow cell to achieve a nanopore sensor that has been used to measure the translocation behaviors of bovine serum albumin(BSA).The results have demonstrated the capability of the sensor in protein denaturation identification.This low-cost and highthroughput technique to fabricate solid-state nanopores on flexible polymeric membranes may facilitate the development of more nanopore-based flexible sensors that can be integrated with other flexible components for wearable diagnosis.

Thin,soft,skin-integrated electronics for real-time and wireless detectionof uricacid in sweat

Wearable sweat sensors are gaining significant attention due to their unparalleled potential for noninvasive health monitoring.Sweat,as a kind of body fluid,contains informative physiological indicators that are related to personalized health status.Advances in wearable sweat sampling and routing technologies,flexible,and stretchable materials,and wireless digital technologies have led to the development of integrated sweat sensors that are comfortable,flexible,light,and intelligent.Herein,we report a flexible and integrated wearable device via incorporating a microfluidic system and a sensing chip with skin-integrated electronic format toward in-situ monitoring of uric acid(UA)in sweat that associates with gout,cardiovascular,and renal diseases.The microfluidic system validly realizes the real-time capture perspiration from human skin.The obtained detection range is 5-200μM and the detection limit is 1.79μM,which offers an importance diagnostic method for clinical relevant lab test.The soft and flexible features of the constructed device allows it to be mounted onto nearly anywhere on the body.We tested the sweat UA in diverse subjects and various body locations during exercise,and similar trends were also observed by using a commercial UA assay kit.

Interplay between entanglement and crosslinking in determining mechanical behaviors of polymer networks

In polymer physics,the concept of entanglement refers to the topological constraints between long polymer chains that are closely packed together.Both theory and experimentation suggest that entanglement has a significant influence on the mechanical properties of polymers.This indicates its promise for materials design across various applications.However,understanding the relationship between entanglement and mechanical properties is complex,especially due to challenges related to length scale constraints and the diffculties of direct experimental observation.This research delves into how the polymer network structure changes when deformed.We specifically examine the relationship between entanglement,crosslinked networks,and their roles in stretching both entangled and unentangled polymer systems.For unentangled polymers,our findings underscore the pivotal role of crosslinking bond strength in determining the system's overall strength and resistance to deformation.As for entangled polymers,entanglement plays a pivotal role in load bearing during the initial stretching stage,preserving the integrity of the polymer network.As the stretching continues and entanglement diminishes,the responsibility for bearing the load increasingly shifts to the crosslinking network,signifying a critical change in the system's behavior.We noted a linear correlation between the increase in entanglement and the rise in tensile stress during the initial stretching stage.Conversely,the destruction of the network correlates with a decrease in tensile stress in the later stage.The findings provide vital insights into the complex dynamics between entanglement and crosslinking in the stretching processes of polymer networks,offering valuable guidance for future manipulation and design of polymer materials to achieve desired'mechanical properties.

Terahertz frequency selective surfaces using heterostructures based on two-dimensional diffraction grating of single-walled carbon nanotubes

For single-walled carbon nanotubes(SWCNTs)with a length of 1-50μm,the surface plasmon-polariton(SPP)resonance is within the terahertz frequency range;therefore,SWCNT lattices can be used to design frequency-selective surface(FSS).A numerical model of electromagnetic wave diffraction on a two-dimensional periodic SWCNT lattice can be described by an integro-differential equation of the second-order with respect to the surface current along SWCNT.The equation can be solved by the Bubnov-Galerkin method.Frequency dependence of reflecting and transmitting electromagnetic waves for FSSs near the SPP resonance is studied numerically.It is shown that the resonances are within the lowerfrequency part of the terahertz range.We also estimate the relaxa-tion frequency of an individual SWCNT and demonstrate the applic-ability of the Kubo formula for graphene conductivity to array of strips similar in size to SWCNTs under consideration.

Porous polyurethane hydrogels incorporated with CMC for eliminating methylene blue from water

Here,a series of polyurethane porous hydrogels(PUF-s)loaded with different sodium carboxymethyl cellulose(CMC)were successfully prepared by one-step foaming method.The physio-chemical prop-erties and morphologies were characterized.The effects of CMC content,adsorbent dosage,temperature,pH value and other fac-tors on the adsorption of methylene blue(MB)dye in water by CMC-PUF-s were also investigated through static adsorption experi-ments.The results showed that CMC-PUF-10 had excellent adsorp-tion performance for MB solution with removal rate of 81.47%,and the maximum adsorption capacity was 27.5 mg/g.In addition,the study of adsorption kinetics and adsorption isotherms showed that the adsorption of MB by CMC-PUF was more consistent with Langmuir isotherm adsorption model and pseudo second-order kinetic model.The adsorption thermodynamics study suggested that the adsorption process of MB by CMC-PUF-10 was sponta-neous and exothermic at room temperature.The results of cyclic adsorption experiment demonstrated that the removal rate of MB reached above 70%after five cycles,indicating the foams with excellent recyclability.Finally,a low-cost,environmentally friendly and recyclable MB adsorbent was synthesized in this study.As polyurethane foam was synthesized by one-step foaming method,this adsorbent can be prepared on site in practical application and reduce the transportation cost.

Adjustable volume and loading release of shape memory polymer microcapsules

Research on microcapsules has been conducted in recent years given trends in miniaturization and novel functionalization.In this work,we designed and prepared a series of unique shape memory polyurethane(SMPU)microcapsules with stimuli-responsive func-tions.The microcapsule has a core-shell structure in which the surface morphology can be adjusted,and it has a certain loadbearing capacity.In addition,the SMPU microcapsule has a stimuliresponsive function for shape memory and solvent response.The temperature of its shape recovery is approximately body tempera-ture,and it can swell to rupture under the stimulation of organic solvents.Thus,the SMPU microcapsule has potential applications in biomedical fields,such as drug release.

A novel smart steel strand based on optical-electrical co-sensing for full-process and full-scale monitoring of prestressing concrete structures

As the main load bearing component,the steel strand has a significant impact on the safety of civil infrastructure.Real-time monitoring of steel strand stress distribution throughout the damage process is an impor-tant aspect of civil infrastructure health assessment.Hence,this study proposes an optical-electrical co-sensing(OECS)smart steel strand with the DOFS and CCFPI embedded in.It can simultaneously measure small strains in the initial damage phase with high accuracy and obtain information in the large deformation phase with relatively low precision.Several experiments were carried out to test its sensing performance.It shows both DOFS and CCFPI have good linearity,repeatability and hysteresis.In comparison to DOFS,CCFPI has a relatively lower accuracy and resolution,but a large enough measurement range to tolerate the large strain in the event of a steel strand failure.To verify the reliability of the proposed smart steel strand in real structures,the strand strain distribution in the full damage process of bonded prestressed beams under four-point bending loading was monitored using the smart steel strand as a prestressing tendon.The strain measured by the OECS steel strand is shown to reflect the deformation and stiffness variation of prestressed beams under different load.

Optimal alignment for maximizing the uniaxial modulus of 2D anisotropic random nanofiber networks

Nanofiber networks are effective structural forms to utilize the excellent nanoscale properties of nanofibers in macro scale.Properly tuning the anisotropic degree of fiber orientation distribution can maximize the macroscopic mechanical properties of random nanofiber networks in a specific direction.However,the reinforcing mechanism of the anisotropic orientation distribution to the elastic behavior has not been fully understood.In this paper,the effect of anisotropic orientation distribution of nanofibers on the elastic behavior of network is studied based on the modulus-density scaling relation and stiffness thresholds.The uniaxial modulus of network is determined by both the orientation angle of each fiber and interconnectivity of the random fiber network.With the increase of anisotropic degree,the contribution of fiber orientation angle to the network modulus of the preferential direction increases and gradually tends to a constant,while the interconnectivity of the networks decreases,which may reduce the loadability of network.Therefore,at a given network density,the uniaxial modulus along the preferential direction first increases to a maximum value and then decreases with the increase of the anisotropic degree.Furthermore,an expression to predict the optimal anisotropic degrees corresponding to the maximum uniaxial moduli at different network densities is established.

Effect of grain boundary segregation on aging resistance and mechanical properties of tetravalent element-doped 3Y-TZP ceramics for dental restoration

In the humid oral environment,3Y-TZP ceramics always suffer from low-temperature degradation(LTD)for a long time,which results in the degradation of mechanical properties and catastrophic failure.The low-temperature degradation(LTD)and mechanical properties of low-cost tetravalent(Ge^(4+),Ti^(4+))element-doped 3Y-TZP were investigated by analysing grain boundary segregation in samples with deferent contents.The results show that GeO_(2) is superior to TiO_(2) in limiting LTD but results in lower flexural strength and fracture toughness when the content is≥1.5 mol%.This dilemma can be improved by adding only 0.1%-0.5 wt%Al_(2)O_(3),and the flexural strength and fracture toughness of 0.25 wt% Al_(2)O_(3) zirconia are then increased to 898 MPa and 4.68 MPa·m^(1/2) compared with 1Ge-3Y,respectively.This work is expected to provide an effective reference for the development and application of budget dental materials.

Thermally driven carbon nanotube@polycaprolactone coaxial artificial muscle fibers working in subzero environments

Artificial muscle fibers driven electrothermally with excellent properties of response,stroke,and work capacity are expected to serve in some intelligent structures and systems.However,muscle fibers that operate in subzero environments are highly needed in industrial production and aerospace applications but remain challenging.Herein,we reported a coaxial artificial muscle fiber by electrospinning a sheath of polycaprolactone(PCL)nanofibers on the surface of a carbon nanotube(CNT)fiber core,achieving the actuation in response to thermal at subzero temperatures.The CNT@PCL coaxial muscle fiber under 0.3 MPa achieved a maximum contractile stroke of~18%as the temperature changed from−130℃ to 45℃.The actuation mechanism at subzero temperatures of this muscle fiber was analyzed in combination with the temperature-deformation schematic curve of different polymers.Furthermore,a temperature sensor based on this muscle fiber was developed,due to the excellent linear relationship between the contraction and temperature.A 3D-printed prosthetic arm was designed to further exhibit the application demonstrations of this muscle fiber in subzero environments.This work provides new insights into artificial muscle fibers for serving in extreme environments with ultralow temperatures.

Development and sensing performance study of a smart CFRP cable assembled by multi-group anchorage units

Carbon fiber reinforced polymer(CFRP)can be applied for bridge cables due to its excellent properties.As the important load-bearing structural component,real-time force monitoring of the CFRP cable is required.This paper presents a new smart CFRP cable that combines the self-sensing rods with embedded sensors and the anchorage system using extrusion technology.By embedding optical fiber(OF)and coaxial cable Fabry-Perot interferometer(CCFPI)into CFRP rods respectively,two types of self-sensing rods(CFRP-OF rod and CFRP-CCFPI rod)were fabricated.A new anchorage unit using an extrusion process was proposed as a basic component of smart CFRP cables.Anchorage units holding a CFRP-OF rod and a CFRP-CCFPI rod were tested to obtain their sensing and mechanical properties.Three ancho-rage units were assembled to form a smart CFRP cable with self-sensing functionality.A verification test was carried out to confirm the capabil-ity of monitoring the cable force.The test results demonstrate that the smart CFRP cable composed of multiple anchorage units has good potential in bridge engineering.

A thermoviscoelastic finite deformation constitutive model based on dual relaxation mechanisms for amorphous shape memory polymers

This paper proposes a new thermoviscoelastic finite deformation model incorporating dual relaxation mechanisms to predict the complete thermo-mechanical response of amorphous shape memory polymers.The model is underpinned by the detailed microscopic molecular mechanism and effectively reflects the current understanding of the glass transition phenomenon.Novel evolution rules are obtained from the model to characterize the viscous flow,and a new theory named an internal stress model is introduced and combined with the dual relaxation mechanisms to capture the stress recovery.The rationality of the constitutive model is verified as the theoretical results agree well with the experimental data.Moreover,the constitutive model is further simplified to facilitate engineering applications,and it can roughly capture the characteristics of shape memory polymers.

The frequency-dependent polarization switching in nanograined BaTiO_(3) films under high-strength electric field

The polarization reorientation in ferroelectric nanomaterials under high-strength AC electric fields is intrinsically a frequency-dependent process.However,the related study is not widely seen.We report a phase-field investigation regarding the dynamics of polarization switching and the electromechanical characteristics of a polycrystalline BaTiO_(3) nanofilm under applied frequency from 0.1 to 80 kHz.The grain boundaries and the in-plane strains are considered in the model.The obtained hysteresis and butterfly loops exhibit a remarkable variety of shapes with the changing frequency.The underlying mechanism for the observed frequency-dependent physical properties was discussed via domain structure-based analysis.In addition,we examined the influence of the kinetic coefficient in the Ginzburg-Landau equation as well as the influence of the electric-field amplitude to the frequency dependency.It was found that a higher value of kinetic coefficient or field amplitude tends to enhance the mobility of polarization switching and to transform high-frequency characteristics to low-frequency ones.

Sinusoidally architected helicoidal composites inspired by the dactyl club of mantis shrimp

The impact region of the dactyl club of mantis shrimp features a rare sinusoidally helicoidal architecture,contributing to its efficient impact-resistant characteristics.This study aims to attain bioinspired sinusoidally architected composites from a practical engineering way.Morphological features of plain-woven fabric were characterized,which demonstrated that the interweaving warp and weft yarns exhibited a sinusoidal architecture.Interconnected woven composites were thus employed and helicoidally stacked to achieve the desired structure.Quasi-static three-point bending and low-velocity impact tests were subsequently performed to evaluate their mechanical performance.Under three-point bending condi-tion,the dominant failure mode gradually changed from fiber breakage to delamination with the increase in the pitch angle.Failure displacement and energy absorption of the heli-coidal woven composites were,respectively,43.89%and 141.90%greater than the unidirectional ones.Under low-velo-city impact condition,the damage area of the helicoidal woven composites decreased by 49.66%while the residual strength increased by 10.10%compared with those of the unidirectional ones,exhibiting better damage resistance and tolerance.Also,effects of fiber architecture on mechanical properties were examined.This work will shed light on future design of the next-generation impact-resistant architected composites.

A systematic design of multifunctional lattice structures with energy absorption and phononic bandgap by topology and parameter optimization

Lattice structure can realize excellent multifunctional charac-teristics because of its huge design space,and the cellular configuration directly affects the lattice structural performance and lightweight.A novel energy-absorbing multifunctional lat-tice structure with phononic bandgap is presented by topol-ogy and parameter optimization in this paper.First,the two-dimensional(2D)cellular configuration is lightweight designed by using independent continuous mapping(ICM)topology optimization method.The 2D cell is reconstructed by geo-metric parameters and rotated into a three-dimensional(3D)cell by using chiral shape to achieve bandgap.Subsequently,the surrogated model with energy absorption as the object and first-order natural frequency as the constraint is estab-lished to optimize a parametric 3D cell based on the Response Surface Methodology(RSM).Finally,the lattice struc-tures are assembled with dodecagonal staggered arrange-ments to avoid the deformation interference among the adjacent cells.In addition,the lattice structural energy absorp-tion and bandgap characteristics are analyzed and discussed.Compared to Kelvin lattice structure,the optimal lattice struc-ture shows significant improvement in energy absorption effi-ciency.Besides,the proposed design also performs well in damping characteristics of the high-frequency and wide-bandgap.The lattice structural optimization design framework has great meaning to achieve the equipment structural light-weight and multi-function in the aerospace field.

Theoretical study of the electroactive bistable actuator and regulation methods

Dielectric elastomer actuators have attracted growing interest for soft robot due to their large deformation and fast response.However,continuous high-voltage loading tends to cause the electric breakdown of the actuator due to heat accumulation,and viscoelasticity complicates precise control.The snap-through bistability of the Venus flytrap is one of the essential inspirations for bionic structure,which can be adopted to improve the shortcoming of dielectric elastomer actuators and develop a new actuation structure with low energy consumption,variable configuration,and multi-mode actuation.Hence,in this paper,the structural design principles of electroactive bistable actuators are first presented based on the total potential energy of the structure.Following that,a feasible design parameter region is provided,the influence of crucial parameters on the actuation stroke,trigger voltage,and actuation charge are discussed.Finally,according to the coupling relationship between the bending stiffness and the bistable property of the actuator,the adjusting methods of bistable actuation are explored.A qualitative experiment was performed to verify the feasibility and correctness of the bistable design methodology and the actuation regulation strategy.This study provides significant theoretical guidance and technical support for developing and applying dielectric elastomer actuators with multi-mode,high-performance,and long-life characteristics.