Macroscale Surface Research Articles

Leaf Vein-Inspired Superhydrophilic Microchannels for Sustainable Fog Collection.

Fog collection is a promising solution for mitigating the urgent water shortage around the world. Despite the delicate design of various bionic fog harvesting surfaces with prowess to enable fast fog capture and programmed water transport, achieving sustainable and efficient fog collection by regulating the macroscale surface refreshment efficacy remains rarely concerned yet is effective. Here, we proposed a bioinspired structural design to achieve significant improvement on the surface refreshment efficacy to 46.47%, nearly 5 times larger than that of conventional design. Specifically, we constructed superhydrophilic vein-like microchannels on a superhydrophobic brass surface by using laser texture technology and hydrothermal treatment. Our microchannel design acts as a "highway" for synergically transporting and converging the collected fog droplets, as well as rapidly refreshing large surface area for the subsequent fog collection, reminiscent of the leaf veins responsible for the persistent mass transport between plant tissues. The practical implementation also convinced our design of a maximum water collection efficiency of up to 506.67 mg cm-2 h-1 and a long-term performance stability within a 10 h test. Our design is generic to most of the fog harvesting materials, showing great application potential for efficient atmospheric fog collection.

High-speed wafer surface defect detection with edge enhancement via optical spatial filtering in serial time-encoded imaging

With the rapid development of the chip and metasurface industries, high-speed defect detection of wafer during semiconductor batch manufacturing has become increasingly important for yield control. Here, we propose a high-speed, macro-scale wafer surface defect detection method with enhanced image edges, via optical spatial filtering in serial time-encoded imaging. By using blazed gratings to spatially project different wavelength components of pulsed light into a one-dimensional line, together with dispersive Fourier time stretching technology, a high-speed serial time-encoded imaging system based on a single pixel detector is constructed for testing the wafer surface defects, and optical spatial filtering is introduced to improve the imaging quality. Experiments show high-pass spatial filtering effectively restrains environmental interference and enhances image edge detection. Small target detection is achieved without a complex image algorithm. Our solution extends optical spatial filtering to serial time-encoded imaging, not only permitting wafer macro scale defect detection with edge enhancement, but also having potential significance for imaging lidar, imaging spectrometers, ghost imaging technology, and more.

Droplet asymmetry bouncing on structured surfaces: A simulation based on SPH method

The impact of a liquid droplet onto a macro-structured super-hydrophobic surface, results in an asymmetric spreading-retraction process and a significant decrease in contact time. The process involves large deformation of droplets and evolution of surface morphology, so it is difficult to efficiently simulate using traditional grid-based methods. In this study, a numerical model is established using the mesh-free smoothed particle hydrodynamics (SPH) method to simulate the interaction of liquid droplets with solid surfaces exhibiting complex macro-textures. Leveraging the Lagrange nature of SPH, liquid droplets can be model using free surface boundary condition. The weakly compressible SPH formulation is employed to discretize the governing equations of liquid. Surface tension is captured by introducing an additional negative pressure term, inducing attractive forces among fluid particles. Kernel functions are carefully chosen to mitigate stress instability resulting from droplet spreading and retraction. The model is then applied to simulate the dynamic processes of droplets impact on flat and non-flat super-hydrophobic surfaces. The bouncing dynamics of droplets are investigated under varying conditions, including Weber number, size, and morphology of macro-scale surface structures. Our simulation results for contact time, maximum diameter, and droplet morphology align closely with experimental observations. The contact time of the droplet exhibits a dependency on its size and surface geometry, with a transition towards planar geometry diminishing asymmetric spreading effects. The findings highlight the significance of Weber number and cylinder diameter in determining contact time, providing insights for the design of optimized surface structures for specific droplet impact parameters. In addition, the use of a free-surface condition for modeling proved computationally efficient for 3D simulations. The model effectively reproduces nonlinear behaviors such as droplet spreading, splashing, and bouncing, highlighting the significant advantage of SPH in simulating such problems.

Continuous printing of bone-inspired hierarchical porous objects using video projection-based stereolithography

Bone-inspired porous structures have attracted intense attention in biomedical and mechanical applications due to their unique combination of strength, toughness, and low weight. Although layer-by-layer-based additive manufacturing techniques can build structures with high geometric complexity, it remains challenging to fabricate porous objects with gradient porosity and pore size ranging from nano- to micro-scale. This research investigates the video projection-based stereolithography (VP-SL) process, which is a continuous 3D printing process, also known as Continuous Liquid Interface Production (CLIP), for fabricating hierarchical porous structures with nano-, micro- and macro-scale pores and surface features. This work tested the hypothesis that tuning the printing speed during the VP-SL process can generate an imbalance between curing and resin recoating, resulting in pores in cured polymer. First, the VP-SL process, setup, and the mechanisms of forming micropores and nanowrinkles were introduced. Then, the printing range of the VP-SL process was characterized using curing depth experiments. To validate the efficiency and feasibility of the proposed approach, various three-dimensional hierarchical structures were fabricated with homogeneous and gradient porosity, and the effect of porosity distribution on mechanical properties was studied. Test cases were printed and characterized to validate the feasibility and efficiency of the proposed approach. The results demonstrated the capability of the VP-SL process and its potential in the production of gradient porous objects for various applications, such as scaffolds for custom bone implants.

Enhancement of quenching heat transfer performance through destabilization of vapor film

Film boiling is typically the rate-limiting process during quenching relevant to manufacturing, material processing, and vitrification. Here, we report on the effect of macroscale surface extends (fins) and microscale textures on the enhancement of quenching heat transfer performance. At a quench pool temperature of 80 °C, the pin-finned surfaces with hierarchical roughness decrease the quench duration by 4.5 times, 3.4 times, and 1.3 times compared to a plane, annular-finned, and pin-finned substrates, respectively. Annular and pin-finned surface extends influence the vapor geometry in the film boiling regime and trigger a premature collapse of the vapor film on vertical cylinders, elevating the minimum film boiling temperature. The pin fins enable higher heat transfer in the film and transition boiling regimes by disrupting the vapor film while providing a pathway for vapor escape, unlike annular fins. The hierarchical surfaces with microtextures etched on the pin fins further increase heat dissipation by offering nucleation sites. We discuss the role of surface textures on the range of temperatures that sustain the transition boiling regime during quenching.

Stochastic‐Deep Learning Parameterization of Ocean Momentum Forcing

AbstractCoupled climate simulations that span several hundred years cannot be run at a high‐enough spatial resolution to resolve mesoscale ocean dynamics. Recently, several studies have considered Deep Learning to parameterize subgrid forcing within macroscale ocean equations using data from ocean‐only simulations with idealized geometry. We present a stochastic Deep Learning parameterization that is trained on data generated by CM2.6, a high‐resolution state‐of‐the‐art coupled climate model. We train a Convolutional Neural Network for the subgrid momentum forcing using macroscale surface velocities from a few selected subdomains with different dynamical regimes. At each location of the coarse grid, rather than predicting a single number for the subgrid momentum forcing, we predict both the mean and standard deviation of a Gaussian probability distribution. This approach requires training our neural network to minimize a negative log‐likelihood loss function rather than the Mean Square Error, which has been the standard in applications of Deep Learning to the problem of parameterizations. Each estimate of the conditional mean subgrid forcing is thus associated with an uncertainty estimate–the standard deviation—which will form the basis for a stochastic subgrid parameterization. Offline tests show that our parameterization generalizes well to the global oceans and a climate with increased levels without further training. We then implement our learned stochastic parameterization in an eddy‐permitting idealized shallow water model. The implementation is stable and improves some statistics of the flow. Our work demonstrates the potential of combining Deep Learning tools with a probabilistic approach in parameterizing unresolved ocean dynamics.

The effect of a novel pillar surface morphology and material composition demonstrates uniform osseointegration

Long-term survival of orthopedic implants requires a strong and compliant interface between the implant and surrounding bone. This paper further explores the in-vivo response to a novel, macro-scale osseointegration surface morphology. In this study, we examine the effects of material composition on osseointegration in relation to the controlled surface geometry. The pillared surface is constructed of discontinuous surface geometry which creates an open space for unencumbered bone migration. In creating an open, macro-scale morphology we have demonstrated a bone migration and integration that is less dependent on the underlying implant material and is substantially driven thru surface geometry.In this in-vivo study an established ovine model was used to examine the effects of implant material composition on bone ingrowth and mechanical performance. Cortical and cancellous sites in the tibia and distal femur were examined at 6 and 12 weeks with μCT, histology, histomorphometry, and mechanical performance. Implant materials tested included PEEK (Evonik, VISTAKEEP®), PEEK HA (Invibio, PEEK-OPTIMA HA Enhanced), Titanium coated PEEK, Titanium (Ti–6Al–4V, Grade 5), and Ultra-High Molecular Weight Polyethylene (UHMWPE). Extensive bone ingrowth was noted in all implant materials at 12 weeks with maturation of the bone within the pillar structure from 6 weeks to 12 weeks. Histology demonstrated little fibrous deposition at the implant interface with no adverse cellular reactions. Histomorphometric review of cortical sites revealed greater than 60% bone ingrowth at 6 weeks increasing to nearly 80% by the 12 week timepoint. Cancellous sites yielded a mean of 30% ingrowth at 6 weeks increasing to 35% by 12 weeks. Pushout testing of cortical site samples demonstrated increase in pushout force between the 6 and 12 week timepoints. Increases were significant in all but the UHMWPE samples. Stiffness likewise increased in all samples between the two times.These results demonstrated the effectiveness of the pillar morphology with full integrating from the surrounding bony tissue regardless of the material.

Two-scale homogenization of hydrodynamic lubrication in a mechanical seal with isotropic roughness based on the Elrod cavitation algorithm

A two-scale homogenization method for modelling the hydrodynamic lubrication of mechanical seals with isotropic roughness was developed and presented the influence of surface topography coupled into the lubricating domain. A linearization approach was derived to link the effects of surface topography across disparate scales. Solutions were calculated in a polar coordinate system derived based on the Elrod cavitation algorithm and were determined using homogenization of periodic simulations describing the lubrication of a series of surface topographical features. Solutions obtained for the hydrodynamic lubrication regime showed that the two-scale homogenization approach agreed well with lubrication theory in the case without topography. Varying topography amplitude demonstrated that the presence of surface topography improved tribological performance for a mechanical seal in terms of increasing load-carrying capacity and reducing friction coefficient in the radial direction. A Stribeck curve analysis was conducted, which indicated that including surface topography led to an increase in load-carrying capacity and a reduction in friction. A study of macro-scale surface waviness showed that the micro-scale variations observed were smaller in magnitude but cannot be obtained without the two-scale method and cause significant changes in the tribological performance.

Shear-area variation: A mechanism that reduces hydrodynamic friction in macro-textured piston ring liner contacts

Using a reciprocating rig to simulate the piston ring-cylinder liner contact, we show that macro-scale surface texture yields friction reductions in the hydrodynamic regime of up to 35%. Based on these experimental observations, we put forward a new macro-texture induced friction reduction mechanism and validate it through theoretical 1D modelling. This “Shear-Area Variation” mechanism involves macro-texture reducing both the sheared contact area (acting to decrease friction) and hydrodynamic load support/lubricant film thickness (acting to increase shear-rate and hence friction). Provided the oil film is thick enough to prevent asperity contact, the area reduction effect dominates the friction response. This has implications for machine efficiency improvements, as friction is reduced around mid-stroke where sliding speed and energy dissipation is greatest. It also complements the majority of surface texture research which involves micro-scale texture that is only effective at low speeds in the mixed and boundary regimes (around top and bottom- dead centre).

Multi-scale characterization of the effect of saturated steam on the macroscale properties and surface changes of moso bamboo

Bamboo is a woody material that has become a key substitute for wood resources in many fields. This study is aimed to analyze the effects of saturated steam (140, 160, 180 °C) on physical, crystallinity, chemical composition, mechanical properties as well as microstructures at different periods (4, 6, 8, 10 min). Expectedly, a reduction of hemicellulose and cellulose and increment of relative content of lignin in bamboo when temperature above 160 °C was positive to reduce the equilibrium moisture content (EMC). Thus, the hygroscopicity improved and the parenchyma cells and vascular bundles were shrunk slightly. Both temperature and time positively affected the crystallinity of bamboo samples in comparison with the control. Heat treatment parameters affect the mechanical properties of bamboo. When the treatment was carried out at 140 °C, the modulus of rupture (MOR) and modulus of elastic (MOE) increased in comparison to no treatment; Furthermore, The MOR and MOE decreased by 40% and 19% compared with that of the untreated bamboo at 180 °C for 10 min. The temperature and time had a great influence on a*, b*, and L* of the bamboo. The results showed that during the heat treatment, the bamboo color changed from light yellow to dark red-brown, and the overall color changed evenly. Among them, a* increased firstly and then decreased, indicating that the treated bamboo was reddish, while b* and L* mainly showed a downward trend. The ΔE value positively corresponded to heat treatment severity.

In-Vivo response to a novel pillared surface morphology for osseointegration in an ovine model

Primary stability and secondary fixation of orthopedic implants to bony tissues are important for healing and long-term functionality. Load sharing and stress transfer are key requirements of an effective implant/tissue interface. This paper presents a novel, macro-scale osseointegration surface morphology which addresses the implant/tissue interface from both the biologic as well as biomechanical perspective. The surface morphology is a controlled, engineered, open topography manifested as discrete pillars projecting from the implant enabling continuous bone ingrowth.The pillared surface is distinct from other porous surfaces and can be differentiated by the localization of the implant material into discrete pillars enabling a continuous mass of bone to freely and easily interdigitate into the pillared structure. Traditional porous structures distribute the implant material throughout the surface forcing the bone to grow in a discontinuous manner. Creating an open and continuous space or “open porosity” in and around the pillar structure allows the bone to easily interdigitate with the implant surface without encumberment from a continuous porous structure.An in-vivo study, using an established ovine model, was undertaken examining the effects of pillar morphology on bone ingrowth and mechanical performance. Cortical and cancellous sites were evaluated utilizing histology, histomophometry, and mechanical pushout, at 4 and 12 weeks. Robust bone ingrowth occurred for all morphologies as was noted in review of the study results. An increase in volume and maturity of bone was noted between the intermediated and final time points. Histomophometry demonstrated over 40% and 80% new bone occupied the available “ingrowth” area at 12 weeks for cancellous and cortical sites (respectively). Histologic review showed little fibrous tissue ingrowth at the interface with no adverse cellular reactions. Testing of cortical samples demonstrated a significant increase in pushout load between the 4 and 12 week timepoints and a 4–8 fold increase in pushout load as compared to the grit blast control. These results demonstrated the effectiveness of the novel interface for orthopedic applications in an in-vivo ovine model.

Effects of multi-scale heterogeneity on the simulated evolution of ice-rich permafrost lowlands under a warming climate

Abstract. In continuous permafrost lowlands, thawing of ice-rich deposits and melting of massive ground ice lead to abrupt landscape changes called thermokarst, which have widespread consequences on the thermal, hydrological, and biogeochemical state of the subsurface. However, macro-scale land surface models (LSMs) do not resolve such localized subgrid-scale processes and could hence miss key feedback mechanisms and complexities which affect permafrost degradation and the potential liberation of soil organic carbon in high latitudes. Here, we extend the CryoGrid 3 permafrost model with a multi-scale tiling scheme which represents the spatial heterogeneities of surface and subsurface conditions in ice-rich permafrost lowlands. We conducted numerical simulations using stylized model setups to assess how different representations of micro- and meso-scale heterogeneities affect landscape evolution pathways and the amount of permafrost degradation in response to climate warming. At the micro-scale, the terrain was assumed to be either homogeneous or composed of ice-wedge polygons, and at the meso-scale it was assumed to be either homogeneous or resembling a low-gradient slope. We found that by using different model setups and parameter sets, a multitude of landscape evolution pathways could be simulated which correspond well to observed thermokarst landscape dynamics across the Arctic. These pathways include the formation, growth, and gradual drainage of thaw lakes; the transition from low-centred to high-centred ice-wedge polygons; and the formation of landscape-wide drainage systems due to melting of ice wedges. Moreover, we identified several feedback mechanisms due to lateral transport processes which either stabilize or destabilize the thermokarst terrain. The amount of permafrost degradation in response to climate warming was found to depend primarily on the prevailing hydrological conditions, which in turn are crucially affected by whether or not micro- and/or meso-scale heterogeneities were considered in the model setup. Our results suggest that the multi-scale tiling scheme allows for simulating ice-rich permafrost landscape dynamics in a more realistic way than simplistic one-dimensional models and thus facilitates more robust assessments of permafrost degradation pathways in response to climate warming. Our modelling work improves the understanding of how micro- and meso-scale processes affect the evolution of ice-rich permafrost landscapes, and it informs macro-scale modellers focusing on high-latitude land surface processes about the necessities and possibilities for the inclusion of subgrid-scale processes such as thermokarst within their models.

Sonolithography: In‐Air Ultrasonic Particulate and Droplet Manipulation for Multiscale Surface Patterning

AbstractAcoustic fields are increasingly being used in material handling applications for gentle, noncontact manipulation of particles in fluids. Sonolithography is based on the application of acoustic radiation forces arising from the interference of ultrasonic standing waves to direct airborne particle/droplet accumulation in defined spatial regions. This approach enables reliable and repeatable patterning of materials onto a substrate to provide spatially localized topographical or biochemical cues, structural features, or other functionalities that are relevant to biofabrication and tissue engineering applications. The technique capitalizes on inexpensive, commercially available transducers and electronics. Sonolithography is capable of rapidly patterning micrometer to millimeter scale materials onto a wide variety of substrates over a macroscale (cm2) surface area and can be used for both indirect and direct cell patterning.

Synthesis of Lactic Acid-Based Thermosetting Resins and Their Ageing and Biodegradability.

The present work is focused on the synthesis of bio-based thermoset polymers and their thermo–oxidative ageing and biodegradability. Toward this aim, bio-based thermoset resins with different chemical architectures were synthesized from lactic acid by direct condensation with ethylene glycol, glycerol and pentaerythritol. The resulting branched molecules with chain lengths (n) of three were then end-functionalized with methacrylic anhydride. The chemical structures of the synthesized lactic acid derivatives were confirmed by proton nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared spectroscopy (FT–IR) before curing. To evaluate the effects of structure on their properties, the samples were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and the tensile testing. The samples went through thermo-oxidative ageing and biodegradation; and their effects were investigated. FT-IR and 1H-NMR results showed that three different bio-based resins were synthesized using polycondensation and end-functionalization. Lactic acid derivatives showed great potential to be used as matrixes in polymer composites. The glass transition temperature of the cured resins ranged between 44 and 52 °C. Pentaerythritol/lactic acid cured resin had the highest tensile modulus and it was the most thermally stable among all three resins. Degradative processes during ageing of the samples lead to the changes in chemical structures and the variations in Young’s modulus. Microscopic images showed the macro-scale surface degradation on a soil burial test.

Toward Robust Macroscale Superlubricity on Engineering Steel Substrate.

"Structural superlubricity" is an important fundamental phenomenon in modern tribology that is expected to greatly diminish friction in mechanical engineering, but now is limited to achieve only at nanoscale and microscale in experiment. A novel principle for broadening the structural superlubricating state based on numberless micro-contact into macroscale superlubricity is demonstrated. The topography of micro-asperities on engineering steel substrates is elaborately constructed to divide the macroscale surface contact into microscale point contacts. Then at each contact point, special measures such as pre-running-in period and coating heterogeneous covalent/ionic or ionic/ionic nanocomposite of 2D materials are devised to manipulate the interfacial ordered layer-by-layer state, weak chemical interaction, and incommensurate configuration, thereby satisfying the prerequisites responsible for structural superlubricity. Finally, the robust superlubricating states on engineering steel-steel macroscale contact pairs are achieved with significantly reduced friction coefficient in 10-3 magnitude, extra-long antiwear life (more than 1.0 × 106 laps), and good universality to wide range of materials and loads, which can be of significance for the industrialization of "structural superlubricity."

Surface roughness signatures of summer arctic snow-covered sea ice in X-band dual-polarimetric SAR

ABSTRACT Surface roughness of sea ice is primary information for understanding sea ice dynamics and air–ice–ocean interactions. Synthetic aperture radar (SAR) is a powerful tool for investigating sea ice surface roughness owing to the high sensitivity of its signal to surface structures. In this study, we explored the surface roughness signatures of the summer Arctic snow-covered first-year sea ice in X-band dual-polarimetric SAR in terms of the root mean square (RMS) height. Two ice campaigns were conducted for the first-year sea ice with dry snow cover in the marginal ice zone of the Chukchi Sea in August 2017 and August 2018, from which high-resolution (4 cm) digital surface models (DSMs) of the sea ice were derived with the help of a terrestrial laser scanner to obtain the in situ RMS height. X-band dual-polarimetric (HH and VV) SAR data (3 m spatial resolution) were obtained for the 2017 campaign, at a high incidence angle (49.5°) of TerraSAR-X, and for the 2018 campaign, at a mid-incidence angle (36.1°) of TanDEM-X 1–2 days after the acquisition of the DSMs. The sea ice drifted during the time between the SAR and DSM acquisitions. As it is difficult to directly co-register the DSM to SAR owing to the difference in spatial resolution, the two datasets were geometrically matched using unmanned aerial vehicle (4 cm resolution) and helicopter-borne (30 cm resolution) photographs acquired as part of the ice campaigns. A total of five dual-polarimetric SAR features―backscattering coefficients at HH and VV polarizations, co-polarization ratio, co-polarization phase difference, and co-polarization correlation coefficient ―were computed from the dual-polarimetric SAR data and compared to the RMS height of the sea ice, which showed macroscale surface roughness. All the SAR features obtained at the high incidence angle were statistically weakly correlated with the RMS height of the sea ice, possibly influenced by the low backscattering close to the noise level that is attributed to the high incidence angle. The SAR features at the mid-incidence angle showed a statistically significant correlation with the RMS height of the sea ice, with Spearman’s correlation coefficient being higher than 0.7, except for the co-polarization ratio. Among the intensity-based and polarimetry-based SAR features, HH-polarized backscattering and co-polarization phase difference were analyzed to be the most sensitive to the macroscale RMS height of the sea ice. Our results show that the X-band dual-polarimetric SAR at mid-incidence angle exhibits potential for estimation of the macroscale surface roughness of the first-year sea ice with dry snow cover in summer.

Direct measurement of interaction force between solid surface and air bubble: Relationship between interaction force and contact angle

Estimating the hydrophobicity of a solid surface is important for flotation process. Measuring the contact angle or interaction force between air bubbles and a solid surface has been widely used for evaluating the hydrophobicity of surfaces. However, the correlation between the contact angle and interaction force was not be fully explained because contact angle was measured on a macroscale surface and interaction force was measured on a microscale surface (ranging nm2 – μm2) using atomic force microscopy. In this study, we directly measured the macroscale surface – air bubble interaction force in terms of attachment force and detachment energy. We then correlated our measured attachment force and detachment energy values with the static contact angle of specimen surface. The attachment force (Fa) and detachment energy in phase 2 (E2) represented the hydrophobicity of specimen surface. And Fa and Ed in phase 2 were found to have an exponential relationship until 90° of the surface contact angle.

Optimization of cylinder liner macro-scale surface texturing in marine diesel engines based on teaching–learning-based optimization algorithm

This paper investigates the effect of optimum macro-scale cylinder liners oil groove on the tribological behavior of large bore marine diesel engines. Parabolic bottom shape grooves are selected as the cylinder liner surface texturing. The grooves have been distributed along the stroke in the form of array of circumferential cells with the axial groove centered in each cell. Teaching–learning-based optimization algorithm is applied to get the optimum dimensions of oil grooves, where the objective is to minimize the cyclic average total friction force between the top compression piston ring and the cylinder liner. Numerical simulation based on Reynolds equation is presented to study the effect of optimum grooves’ dimensions on tribological parameters such as hydrodynamic friction, asperity contact pressure, and hydrodynamic oil film pressure. Results showed that the optimum dimensions oil grooves have a significant effect on the total friction force and the cavitation pressure of the oil film.

Dual‐Scale Nanostructures via Evaporative Assembly

AbstractDual‐scale hierarchical structures with regular microscale patterns and varying degree of nanoscale crystalline order are synthesized on physically and chemically homogeneous substrates by evaporative self‐assembly with a suspension of DNA‐functionalized nanoparticles (NPs) with a charged core shell. For a certain NP concentration range, periodic concentric rings in a stripe‐like micropattern are produced over macroscale surface areas by an NP monolayer with hexagonal lattice structure at the nanoscale. The stripe width, spacing, and nanoparticle ordering can be controlled by varying the NP concentration. The results indicate that the interplay between “stick‐slip” motion of the droplet contact line and coulombic and steric NP interactions control the formation of the observed structures. A simple analytical model is proposed to account for the experimental observations and guide the future design of different nanostructure morphologies. This work demonstrates a simple cost‐effective mask‐free method for fabricating large‐area nanostructured 2D materials and metasurfaces for applications ranging from energy conversion/storage to optoelectronics and nanophotonics.

Multi-scale modeling and thermal transfer properties of electric heating fabrics system

Purpose The purpose of this paper is to investigate the thermal transfer properties of electric heating fabric system which contains heating units or conductive yarns by numerical simulation, in order to optimize and evaluate the thermal performance of heating clothing. Design/methodology/approach Two kinds of FEM models are created by ANSYS system: macro-scale models of the fabrics system with heating units and air layer; and meso-scale models of the plain-woven fabrics were established embedded with the stainless yarns. In the macro-scale model, the interior and surface temperature field distribution were simulated and analyzed based on different heating unit size, heating power, heating region, air layer thickness and ambient temperature. For meso-scale models, the effects of the conductive yarns temperature, covering fabrics and pore-filling material on the temperature field distribution were simulated and analyzed. Findings With the increasing of the air layer thickness or the effective conductivity, the heat transfer along the direction of fabric thickness decreases gradually. The heat transfer along the fabric plane can be increased by dispersing the heating region. With the increasing of the conductive yarns’ temperature or the covering fabrics’ conductivity, the heat transfer distance along the fabric warp direction can be increased. Filling the internal pores of the fabric with 10 wt% SiC/TPU hybrid materials can effectively increase the in-plane heat transfer and improve the temperature uniformity on the surface of heated fabrics. Originality/value The finite element method was used to establish the simulation models of the heating fabric systems. The influence of several parameters on the thermal performance was analyzed and discussed, as well as the internal and external temperature distribution in the macro and micro scales models.