High-Efficient Anti-Icing/Deicing Method Based on Graphene Foams.

Anti-icing/deicing has always been a focal issue in modern industries. A novel anti-icing/deicing material based on graphene foams (GF) is prepared in this paper, which integrates multiple functions, including electrothermal conversion, photothermal conversion, and superhydrophobicity. The GF sheet is used as a bottom layer bonded on the protected substrate, which is covered by a polymeric composite coating filled with TiN and SiO2 nanoparticles. Electric heating and light heating experiments are performed to study the anti-icing/deicing performances of such a GF-based material. It is found that, under the unique action of electric fields, a voltage of only 1 V is needed to increase the surface temperature from minus tens of degrees to the one above zero within 400 s, which is much lower than their previous counterparts of more than 10 V to achieve the same unfreezing effect. A slight increase of the applied voltage to 1.5 V can even result in a remarkable increase of the surface temperature from room temperature to more than 150 °C within 200 s, in contrast to existing electric heating techniques to attain peak temperatures of about 100 °C at the expense of tens of volts. Such performances enable the GF-based material to achieve an outstanding electrothermal energy conversion rate of more than 90%. Furthermore, with the help of sunlight illumination in addition to the electric power, not only can the critical voltage to prevent icing be reduced but also a much more rapid and adequate removal of ice or frost from the surface can be realized compared with the deicing/defrosting performance under either electric or light field alone. All of these results demonstrate the obvious advantages of the present method in superior energy utilization efficiency and universal applicability to dark and sunlight environments, which should be particularly useful for at-all-cost protection of key components in industrial equipment from icing.

Fracture strength and failure mechanism of graphene-containing grain boundaries and pores.

Grain boundaries and pores commonly manifest in graphene sheets during experimental preparation. Additionally, pores have been intentionally incorporated into graphene to fulfill specific functions for various applications. However, how does the simultaneous presence of pores and grain boundaries impact the mechanical properties of graphene? This paper establishes uniaxial tension models of single-layer graphene-containing pores and three types of experimentally observed. The effect of interaction between pores and grain boundaries on the fracture strength of graphene was studied respectively for three types of grain boundaries by employing molecular dynamics simulations and considering factors such as pore size, the distance between pores and grain boundaries, and loading angle. A competitive mechanism between the intrinsic strength of pristine graphene with grain boundaries (referred to as pristine GGBs), which varies with the loading angle and the fracture strength of graphene sheets with pores that changes with the size of the pores, governs the fracture strength and failure modes of GGBs with pores. When the former exceeds the latter, the fracture strength of GGBs with pores primarily depends on the size of the pores, and fractures occur at the edges of the pores. Conversely, when the former is lower, the fracture strength of GGBs with pores relies on the loading angle and the distance between pores and grain boundaries, leading to grain boundary rupture. If the two strengths are comparable, the failure modes are influenced by the distance between pores and grain boundaries as well as the loading angle. The findings further elucidate the impact of coexisting grain boundaries and pores on the fracture behavior of graphene, providing valuable guidance for the precise design of graphene-based devices in the future.

Enhanced self-cleaning performance of bio-inspired micropillar-arrayed surface by shear.

Inspired by the sliding behavior of gecko feet during climbing, the contribution of the shear effect to the self-cleaning performance of a bio-inspired micropillar-arrayed surface is studied through a load-shear-pull contact process. It is found that self-cleaning efficiency can be enhanced significantly by shear. The efficiency also depends on microparticle size. For the case of relatively large and small microparticles, self-cleaning efficiency increases first and then almost keeps a constant with the increase of shear distance at different preloads. For medium microparticles, shear can effectively improve self-cleaning efficiency only when the preload is small. The mechanical mechanism under such enhancement is mainly due to the varying contact states between microparticles and micropillars with the shear distance. When the shear distance is large enough, the final self-cleaning efficiency is not sensitive to shear distance anymore because the contact state reaches dynamic equilibrium. Based on such a self-cleaning mechanism of large microparticles, a simple and effective manipulator that can efficiently transfer solid particles is further proposed.

Locust-Inspired Direction-Dependent Transport Based on a Magnetic-Responsive Asymmetric-Microplate-Arrayed Surface.

Inspired by the highly efficient jumping mechanism of locusts, a magnetic-responsive asymmetric-microplate-arrayed surface is designed. Elastic energy can be stored in the microplate and rapidly released by loading and removing a magnetic field. Similar to the bouncing behavior of the locust, objects deposited on the surface of the microplate-arrayed surface will bounce suddenly. It is found that the continuous transport behavior can be induced in the moving magnetic field and the direction-dependent transport is well achieved by preparing the secondary microstructure. The results show that both the weight and transport velocity of the transported object in the forward transport direction are much greater than those in the reverse transport direction. Furthermore, the anisotropic transport property can be strengthened with the increase of the height of the secondary structure. Such surfaces can transport objects with either soft or hard stiffness, as well as objects with different geometric configurations, and the transport path can be arbitrarily programmed. Based on the transport mechanism, a flexible microconvey belt is further designed, which can transport objects in any controlled direction. Such a simple technique can provide new design ideas for directional microtransport requirements.

Simple but Efficient Method To Transport Droplets on Arbitrarily Controllable Paths.

The flexible manipulation of droplets manifests a wide spectrum of applications, such as micro-flow control, drug-targeted therapy, and microelectromechanical system heat dissipation. How to realize the efficient control of droplets has become a problem of concern. In this paper, a simple method that can realize the transport of droplets along any controllable path is proposed. It not only has a simple preparation process and clear transport mechanism but is also easy to realize in manipulation technology. A magnetic-sensitive surface is prepared by filling a polymer matrix with magnetic particles and immersing in a lubricant. Under the action of an external magnetic field, rough microstructures are generated locally on the surface, forming the wettability gradient with the area far away from the field. Moving the magnetic field, the wettability gradient region moves accordingly and drives droplets to transport. To better control the transport path of droplets or realize a more complex path design, a ring-shaped magnetic field is further adopted, during which the droplet is automatically located in the ring-shaped region and moves with the movement of the ring-shaped magnetic field. The present technique is simple and easy to implement, which should be helpful in the field of precise regulation of the droplet position.

One-level microstructure-arrayed hydrophobic surface with low surface adhesion and strong anti-wetting function.

To achieve both a low surface adhesion function and a high anti-wetting function, it is generally necessary to introduce multi-level micro-nano-structures on a surface. However, this will bring the difficulty of preparation technology, and the functions will fail due to the fact that the nanostructures can easily be damaged. In this research, the surface adhesion and anti-wetting properties of several typically one-level microstructure-arrayed hydrophobic surfaces are analyzed with the dynamics theory, including a square pillar-arrayed three-dimensional microstructure, a conical table-arrayed microstructure, and square frustum-arrayed microstructure. It is found that the anti-adhesion performance and anti-wetting property cannot achieve the best performance simultaneously on the one-level microstructure arrayed surfaces. Either the critical pressure of anti-wetting is finite when the surface adhesion is the lowest, or both the anti-adhesion and anti-wetting capacities are finite. However, an interesting phenomenon is found in that the square frustum-arrayed surface can not only achieve an almost infinite anti-wetting capacity when the distance between neighboring microstructures vanishes, but also reach near-zero adhesion when the square frustum reduces to a square pyramid. All the theoretical predictions are further verified by precise numerical simulations. The results of this paper should be helpful for the design of surfaces with low surface adhesion and strong anti-wetting functions in practical engineering.

Directional Transportation on Microplate-Arrayed Surfaces Driven via a Magnetic Field.

Directional transportation on micro/nanostructure-arrayed surfaces driven by an external field has attracted increasing attention in numerous domains, and this has led to significant progress in this field. In this study, an efficient method for high-speed transportation of solid objects is proposed based on magnetically responsive microplate arrays with a high aspect ratio. The transport speed is approximately an order of magnitude higher than the existing value. In addition, the speed of the transported objects can be controlled appropriately by the speed of the magnet. Besides, objects with varying shapes and sizes can be transported in both air and water. Further investigation of the transport mechanism reveals a rapid release of the elastic strain energy stored in the microplate. Hence, using this energy, the object can bounce forward quickly. The proposed technique and design aid not only in studies on more efficient, intelligent, or even programmed micro/nanotransportation but also in micro/nanomanipulation.

Self-Cleaning Performance of the Micropillar-Arrayed Surface and Its Micro-Scale Mechanical Mechanism.

The exceptional adhesive ability of geckos remains almost uninfluenced by contaminated surfaces, showing that the adhesion system of geckos has self-cleaning properties. Although there have been several studies on the self-cleaning performance of geckos and gecko-inspired synthetic adhesives, the microscale mechanical mechanism of self-cleaning is still unclear. In the present study, a micropillar-arrayed surface is fabricated using a template molding method to investigate its self-cleaning performance in a load-pull contact process. The effects of preload, microparticle size on self-cleaning properties are studied. The self-cleaning efficiency of the micropillar-arrayed surface is found to increase with an increase in the microparticle size. For large and small microparticles, self-cleaning efficiency increases with an increase in the preload. For medium microparticles, self-cleaning efficiency first increases and then decreases as the preload increases. The mechanical mechanism underlying such self-cleaning performance is further elucidated; it is mainly attributed to the competition among the elastic energy stored in the micropillars induced by the bending deformation, the interfacial adhesion energy between the microparticles and the deformed micropillars, and the interfacial adhesion energy between the microparticles and substrate, as well as the varying contact states between the microparticles and the deformed micropillars. The preload can not only change the contact states between the microparticles and the micropillar-arrayed surface but also influence the bending elastic energy stored in the micropillars. The results obtained in the present study can help deeply understand the self-cleaning mechanism of micropillar-arrayed surfaces as well as provide a guideline for designing functional surfaces with high self-cleaning efficiency.

Reconfiguring graphene to achieve intrinsic negative Poisson's ratio and strain-tunable bandgap.

A new two-dimensional carbon-based material consisting of pentagonal and hexagonal elements is identified by numerical experiments, which is called phgraphene and possesses not only a tunable semimetallic feature but also a direction-dependent even sign-changed Poisson's ratio. The structural stability of such a new material is first checked systematically. It is found that phgraphene has a similar energy as theγ-graphyne, a thermally stable structure from the room temperature to 1500 K, and elastic constants satisfying the Born-Huang criterion. Both the band structure and density of states are further verified with different techniques, which demonstrate a Dirac semimetallic characteristic of phgraphene. A more interesting finding is that the band structure can be easily tuned by an external loading, resulting in the transition from semimetal to semiconductor or from type I to type III. As a new material that may be applied in the future, the mechanical property of phgraphene is further evaluated. It shows that phgraphene is a typically anisotropic material, which has not only direction-dependent Young's moduli but also direction-dependent even sign-changed Poisson's ratios. The microscopic mechanisms of both the electrical and mechanical properties are revealed. Such a versatile material with tunable band structure and auxetic effect should have promising applications in the advanced nano-electronic field in the future.

How to Achieve a Monostable Cassie State on a Micropillar-Arrayed Superhydrophobic Surface.

Superhydrophobic surfaces with a monostable Cassie state possess numerous interesting applications in many fields, such as microfluidics, oil-water separation, drag reduction, self-cleaning, heat dissipation, and so on. How to guarantee a monostable Cassie state of a superhydrophobic surface is still an interesting problem. In this paper, considering the influence of external interferences that may induce the possible wettability transition, the whole wetting process of a droplet on a trapezoidal micropillar-arrayed superhydrophobic surface is divided into six possible stages. Both the Gibbs-free energy in each stage and the energy barrier between adjacent stages are obtained and analyzed theoretically. It is interesting to find that the finally stable wettability of a trapezoidal micropillar-arrayed superhydrophobic surface significantly depends on the apparent contact angle of the lateral surface of a single micropillar, which can be divided into three regions from 0 to 180°, corresponding to the Wenzel state, metastable Cassie state, and monostable Cassie state. Furthermore, the size of each region is explicitly related to and can be well-tuned by the geometry of microstructures. Such a wettability classification is well verified by a number of existing experimental results and our numerical simulations. As a relatively general case, such a trapezoidal micropillar-arrayed superhydrophobic surface can also be conveniently degenerated to the triangular or rectangular micropillar-arrayed surface. All the results should be useful for the precise design of functional surfaces of different wettabilities.

Directional Sliding Behavior of a Water Droplet on a Wedge-Shape Patterned Functional Surface.

Wedge-shape patterned functional surfaces have attracted considerable interests, due to the application of directional water droplet transport. It has been found that the directional sliding or rolling of water droplets rather than water film spreading on a functional surface is more popular in many applications due to its efficiency. In order to realize the directional sliding of water droplets, a patterned functional surface is well fabricated in the present study, which consists of a hydrophobic wedge-shaped region and a superhydrophobic region. The directional sliding behavior and its influencing factors of water droplet transport on the functional surface are studied experimentally and theoretically. It is found that the three-phase contact line of the water droplet presents three different shapes in the whole sliding process, which are mainly affected by the instant contact angle at the front and rear edges of the water droplet. The sliding velocity of the water droplet is significantly affected by the wedge angle, while the maximum transport displacement depends not only on the wedge angle but also on the static contact angle of the wedge-shape patterned surface and the volume of the water droplet itself. Further comparison shows that the transport displacement of a sliding water droplet is much larger than that of a spreading one. The results should be helpful for the design of functional surfaces with highly efficient water droplet transport, which are needed in the fields of heat transfer, water collection, and drug delivery.

Evaluation on the effect of acupuncture on patients with sepsis-induced myopathy (ACU-SIM pilot study): A single center, propensity-score stratified, assessor-blinded, prospective pragmatic controlled trial.

BACKGROUND: Sepsis-induced myopathy (SIM) is a disease that causes motor dysfunction in patients with sepsis. There is currently no targeted treatment for this disease. Acupuncture has shown considerable efficacy in the treatment of sepsis and muscle weakness. Therefore, our research aims to explore the effects of acupuncture on the improvement of muscle structure and function in SIM patients and on activities of daily living. METHODS: The ACU-SIM pilot study is a single-center, propensity-score stratified, assessor-blinded, prospective pragmatic controlled trial (pCT) with a 1-year follow-up period. This study will be deployed in a multi-professional critical care department at a tertiary teaching hospital in Guangzhou, China. Ninety-eight intensive care unit subjects will be recruited and assigned to either the control group or the acupuncture group. Both groups will receive basic treatment for sepsis, and the acupuncture group will additionally receive acupuncture treatment. The primary outcomes will be the rectus femoris cross-sectional area, the Medical Research Council sum-score and time-to-event (defined as all-cause mortality or unplanned readmission to the intensive care unit due to invasive ventilation). The activities of daily living will be accessed by the motor item of the Functional Independence Measure. Recruitment will last for 2 years, and each patient will have a 1-year follow-up after the intervention. DISCUSSION: There is currently no research on the therapeutic effects of acupuncture on SIM. The results of this study may contribute to new knowledge regarding early muscle atrophy and the treatment effect of acupuncture in SIM patients, and the results may also direct new approaches and interventions in these patients. This trial will serve as a pilot study for an upcoming multicenter real-world study. TRIAL REGISTRATION: Chinese Clinical Trials Registry: ChiCTR-1900026308, registered on September 29th, 2019.

A new Dirac nodal-ring semimetal made of 3D cross-linked graphene networks as lithium ion battery anode materials.

A novel lithium ion battery (LIB) anode material with high capacity is found, which is made of cross-linked graphene sheets. The new material, named bco-C20, has a 3D honeycomb structure composed of unit cells of 20 atoms, and exhibits a body-centered orthorhombic crystal structure. The thermal, dynamic, and mechanical stabilities of such a material are well evaluated by molecular dynamics simulation, phonon dispersion, and Born-Huang criteria. As a promising semimetal, bco-C20 possesses a unique electronic band structure with cross-linked Dirac nodal-rings. The Fermi velocities are from 8.25 × 105 m s-1 to 10.45 × 105 m s-1, indicating good electronic transport properties. A comparison with most of the 3D carbon materials demonstrates that bco-C20 also has the good material properties of high strength and fracture toughness that are very close to those of graphene. Furthermore, a negative Poisson's ratio of up to -0.25 is very helpful for the new material to bear compressive load. Most importantly, as a promising anode material in LIBs, bco-C20 has a high theoretical capacity of 893 mA h g-1, low diffusion barrier of 0.02-0.12 eV, average open-circuit voltage of 0.41 V, and negligible volume change of 3.7%. Some related properties of lithiated bco-C20 are also evaluated and discussed. This study should be helpful for expanding the family of 3D carbon materials with extraordinary properties as well as their promising applications in advanced energy fields.

Therapeutic effect of psoralen on muscle atrophy induced by tumor necrosis factor-α.

OBJECTIVES: To observe and determine the effect and mechanism of psoralen on tumor necrosis factor-α (TNF-α)-induced muscle atrophy. MATERIALS AND METHODS: Three sets of C2C12 cells, including blank control, TNF-α (10 or 20 ng/ml) treatment and a TNF-α (10 or 20 ng/ml) plus psoralen (80 µM) administration were investigated. Cell viability was assessed using Cell Counting Kit-8 (CCK-8) assay. Western blot analysis was used to detect protein expression of atrophic markers. Flowcytometry was used to observe the effect of psoralen on apoptosis. A quantitative real-time PCR (qRT-PCR) assay was performed to detect the mRNA level of miR-675-5P. RESULTS: TNF-α (1, 10, 20 and 100 ng/ml) treatment inhibited C2C12 myoblast viability (P<0.001), while 24 hr of psoralen administration increased the viability, and lowered TNF-α cytotoxicity (P<0.001). MURF1, MAFbx, TRIM62 and GDF15 expressions were significantly increased in TNF-α (10 ng/ml or 20 ng/ml)-treated group (P<0.001), and psoralen could significantly decrease the expression of these proteins (P<0.001). Apoptotic rate of C2C12 myoblasts was increased after TNF-α (10 ng/ml and 20 ng/ml) treatment, and was significantly decreased after psoralen treatment (P<0.001). miR-675-5P was increased in TNF-α-treated C2C12 myoblasts compared to control group, and it was significantly decreased after psoralen treatment. CONCLUSION: Psoralen could reduce TNF-α-induced cytotoxicity, atrophy and apoptosis in C2C12 myoblasts. The therapeutic effect of psoralen may be achieved by down-regulating miR-675-5P.

Flexible Functional Surface for Efficient Water Collection.

Inspired by both the water collection strategy of desert beetles and the lubrication effect of Nepenthes pitcher plants, a new flexible functional surface for water collection is designed and can be easily fabricated. Such a functional surface consists mainly of a superhydrophobic region and a hydrophobic region with infused lubricating oil. Different functional patterns can be easily manipulated by different templates. Due to the flexibility of the surface, not only a two-dimensional surface but also a three-dimensional one can be designed. Directional water collection can be achieved. Furthermore, it is an integrative bioinspired functional surface that does not require any tailoring. Compared with existing functional surfaces, the present surface has higher water collection efficiency in fog and such a function can last 15 days. The functional degraded surfaces can also be easily reused.

Spontaneous dewetting transition of nanodroplets on nanopillared surface.

The spontaneous dewetting transition (SDT) of nanoscale droplets on the nanopillared surface is studied by molecular dynamics simulations. Three typical SDT modes, i.e. condensing, merging and coalescing with flying droplets are observed, and the underlying physical mechanism is clearly revealed by the potential energy analysis of droplets. We find that there exists a dimensionless parameter of the relative critical volume of droplet C cri which completely controls the SDT of nanodroplets. Furthermore, the C cri remains constant for geometrically similar surfaces, which indicates an intrinsic similarity of nanoscale SDT. The effect of pillar height, diameter and spacing on SDT has also been studied and it is likely to occur on the surface with longer, wider and thicker pillars, as well as pillars with cone-like shape and larger hydrophobicity. These results should be useful for a complete understanding of the nanoscale SDT and shed light on the design of smart superhydrophobic surfaces.

Controllable directional deformation of micro-pillars actuated by a magnetic field.

It is well known that special surface functions can be designed by varying the topography of micro-structured surfaces. In the present paper, a simple but effective method to control the directional deformation of micro-pillar arrays is proposed through a rotating magnetic field. The large deformation of each micro-pillar can be tuned by the magnetic field strength and direction. When the magnetic field strength is fixed, the deformation direction of micro-pillars is controlled by the direction of magnetic field. When the direction of magnetic field is determined, the deflection of micro-pillars increases with the increase of magnetic field strength. Based on the principle of minimum potential energy, a theoretical model is further established to disclose such a large deformation mechanism of micro-pillars. The theoretically predicted morphology of deformed pillars is well consistent with the experimental results. The present experimental technique and theoretical results should be useful for the design and preparation of typical functional surfaces such as reversible adhesion, controllable wettability and directional surface transport.

Effect of thin-film length on the peeling behavior of film-substrate interfaces.

Compared with the classical Kendall's model to analyze the steady-state peeling behavior of an infinite length film attaching to a rigid substrate, this paper establishes a model of a finite length thin film adhering on a rigid substrate and analyzes the influence of film's initial adhesion length, film stiffness, and initial cantilever length of films on the whole interface peeling behavior. Both theoretical prediction and finite element calculation are carried out. The typical relationship between the peeling force and the separation distance at the loading point is obtained as well as the morphology of deformed films. It is found that the initial adhesion length has a significant effect on the peeling behavior. Differently from the case of infinite thin films, whether the steady-state peeling process can be achieved or not depends on the film's adhesion length. If the film is long enough, the whole peeling process can be divided into an initial peeling stage, a transition stage, a steady-state stage, and an unstable peeling stage. The maximum peeling force of the interface does not necessarily occur in the steady-state stage, which is influenced by the film's initial adhesion length, film stiffness, and initial cantilever length. The results achieved in this paper can not only provide a systematic understanding of peeling behavior of a thin film on a rigid substrate, but also be helpful for the design of high-quality interface and peeling tests in practical applications.

Spontaneous dewetting of a hydrophobic micro-structured surface.

Inspired by recent experimental observations and natural phenomena that spontaneous dewetting transition occurs on a hydrophobic micro-structured surface, a thermodynamic model of a condensed water droplet on a micro-pillar arrayed surface is established in order to disclose the mechanical mechanism. Based on a general model of an arbitrary-shaped micro-structured surface, surfaces with conical, rectangular and parabolic micro-pillars are investigated. A critical water droplet volume is found, beyond which dewetting transition can be realized. The effect of the micro-pillar's size and intrinsic contact angle on the free energy difference and critical water droplet volume are further studied. The theoretical model may provide a possible explanation for the abnormal Wenzel wetting state of condensed water droplets on lotus leaves and the anti-fogging behavior of a mosquito's compound eyes. The present results should be very useful for the biomimetic design of functional dewetting surfaces in practical applications.

Heavy metal leachability in soil amended with zeolite- or biochar-modified contaminated sediment.

In this work, reuse probability of heavy metal-contaminated sediment for land application was discussed using a 100-day column leaching assessment under the situation of simulated acid rain. For comparison, NaCl-modified zeolite and biochar were firstly studied for their adsorption capacity for Cu, Cd, and Pb in aqueous solution, and then their stabilizing effects on the three metals in sediment-soil mixture. Characteristic results indicated that NaCl-modified zeolite had properties more conducive to metal adsorption than biochar, including higher BET surface area and more negative surface charges. Adsorption capacities of NaCl-modified zeolite fitted by Langmuir isotherm model were 24.83, 35.57, and 133.16 mg g-1 for Cu, Cd, and Pb, respectively. Leaching results demonstrated that metal concentrations in the leachates of soil receiving zeolite- or biochar-modified sediment reduced significantly after 100 days compared with that of soil receiving bare sediment. Moreover, the NaCl-modified zeolite presented a better performance in stabilizing the three metals than biochar from the BCR sequential extraction result. Therefore, stabilization of the dredged contaminated sediment by modified zeolite ensures an environmentally friendly reuse of the sediment on land and makes the sediment treatment operation-able and cost-effective.