Xuemei Chen

Nanjing University of Science and Technology | NJUST

Nature is an important source of inspiration for developing desired structures for various industrial applications. The efficacy of water transport in leaf vein systems provides important insights for the structural design of microchannels. In addition, open microchannels (OMCs) have been reported to effectively reduce the two-phase pressure drop a...

The manifold microchannel heat sink (MMCHS) is a promising design for heat dissipation in high power electronics. However, the configuration of the microchannels in MMCHS is generally rectangular straight channels, which would limit the further improvement of heat transfer performance. Topology optimization has been proven to be an effective approa...

Passive all-day radiative cooling has been proposed as a promising pathway to cool objects by reflecting sunlight and dissipating heat to the cold outer space through atmospheric windows without any energy consumption. However, most of the existing radiative coolers are susceptible to contamination, which may decrease the optical property and gradu...

The targets of divertor are subjected to a huge heat load of 20 MW/m² during the operation of future fusion device. Microchannel cooling technology is an efficient method to dissipate high heat load on the divertor targets. However, the pressure drop of W/Cu flat-type mock-up with traditional rectangular microchannel (RMC) heat sink is particularly...

The problem of ice accumulation causes huge inconvenience in daily life and industrial application. Although superhydrophobic surfaces are promising for preventing ice formation, they may become ineffective in extreme environments. Here, a durable photothermal superhydrophobic surface on aluminum substrate (SHPo‐LIG@Al) is prepared through laser‐in...

Currently, membrane distillation driven by solar energy (solar membrane distillation, SMD) is an effective method to address the high cost and high energy consumption problem of conventional seawater desalination. However, the complex preparation of photothermal membrane and low photothermal conversion efficiency limit the development of SMD. In th...

Topology optimization is an effective method to design heat sinks. In this work, the structural design of the microchannel heat sink (MCHS) was carried out using topology optimization, and a comparative study of the performance of the traditional MCHS and the optimized MCHS under subcooled flow conditions was carried out based on the volume of flui...

As one of the key components of the nuclear fusion reactor, the target of divertor directly faces huge heating power from fusion plasma, and thus its capability to withstand high heat flux is of essential importance for the stability and safety operation of fusion devices. The divertor target needs to meet the heat dissipation requirements of up to...

The Topology Optimization (TO) has been proved to be an effective method for designing Microchannel Heat Sinks (MCHS). However, due to the relatively high computational cost and poor numerical stability, it is still challenging to design the thermo-fluid TO under high Reynolds number (Re). In this work, we propose a Contour Extraction Based on Topo...

Large aspect ratio of microchannels enables the corresponding heat sink possess higher heat transfer capability, however, the generated bubbles tend to rapidly extend forward and backward due to the large aspect ratio of the channels, thereafter blocking the channels, deteriorating the heat dissipation and increasing the pressure loss. Open microch...

As an important component of the tokamak, divertor is mainly responsible for extracting heat and helium ash, and the targets of the divertor need to withstand high heat flux of 10 MW/m2 for steady-state operation. In this work, we proposed a new strategy, using microchannel cooling technology to remove high heat load on the targets of the divertor....

Rapid droplet shedding from surfaces is fundamentally interesting and important in numerous applications such as anti-icing, anti-fouling, dropwise condensation, and electricity generation. Recent efforts have demonstrated the complete rebound or pancake bouncing of impinging droplets by tuning the physicochemical properties of surfaces and applyin...

The conventional straight microchannel heat sinks have been reported to inadequately remove the increasing power density of electronics. In recent years, an effective heat transfer enhancement method, flow disruptions have attracted the attention of researchers, where interrupted structures are arranged in the microchannel to enhance flow mixing an...

Open microchannels heat sink can reduce the pressure drop and mitigate the flow instability, but the influence of wettability on the two-phase flow boiling for open microchannels configuration is unclear. In this study, open microchannels with superhydrophilic (SHPi), hydrophilic (HPi) and superhydrophobic (SHPo) properties were fabricated, respect...

In recent years, researchers have conducted extensive studies on the improvement of heat transfer performance of microchannels, however, exploiting biomimetic microchannels to enhance the flow boiling heat transfer performance is still relatively rare. In this study, inspired by the cobweb structures in nature, cobweb-shaped microchannels with hori...

Carbon nanotube-based (CNT-based) interfacial evaporation material is one of the most potential materials for solar desalination. Here, we studied the evaporation rate of the CNT-based membranes with different hydrophilic and hydrophobic chemical modified surfaces using molecular dynamic simulations. We found that the hydrogen bonding density among...

The manifold microchannel (MMC) heat sink has been used for thermal management of high heat flux electronics. Flow maldistribution among microchannels is one of the major hindrances that affect the proper functioning of the typical-MMC (i.e., a coplanar design of the manifolds and the inlet/outlet ports) cooling system, which is attributed to the Z...

Pressing need goes ahead for accessing freshwater in insufficient supply countries and regions, which will become a restrictive factor for human development and production. In recent years, solar-driven water evaporation (SDWE) systems have attracted increasing attention for their specialty in no consume conventional energy, pollution-free, and the...

The primary problem with membrane distillation (MD) for concentrating hypersaline wastewaters is its severe membrane scaling induced by increasing salt concentration of wastewater. Herein, we developed a superhydrophobic and welded-pore polyimide fibrous membranes (SH-welded PI FM) combined with optimizing feed/permeate flow velocity to alleviate m...

The elastic membranes with different surface stiffness were fabricated via spin-coating followed by the laser ablation. The as-fabricated elastic membrane exhibited superhydrophobicity with a rough microstructure. The droplet impacting experiment on the cold elastic superhydrophobic membrane was conducted, and the influence of surface stiffness and...

Heterogeneous surfaces with wetting contrast have gained extensive attention in recent years because of their potential application in condensation heat transfer enhancement. In this work, we engineered superhydrophobic/hydrophilic hybrid (SHH) surfaces on copper substrates via a laser-ablation process. We demonstrated that the as-fabricated SHH su...

The treatment of hypersaline wastewaters with membrane distillation (MD) is significant but challenging, owing to the critical limitations of severe membrane wetting and fouling. Herein, a monolithic and self-roughened Janus fibrous membrane (FM) with asymmetrical superwettability was developed via sequential electrospinning and electrospraying in...

Learning from nature has traditionally and continuously provided important insights to drive a paradigm shift in technology. In particular, recent studies show that many biological organisms exhibit spectacular surface topography such as shape, size, spatial organization, periodicity, interconnectivity, and hierarchy to endow them with the capabili...

This image depicts a superhydrophilic/superhydrophobic hybrid surface with superhydrophilic triangular patterns on the superhydrophobic substrate, fabricated using a laser ablation approach. The hybrid surface enables fast condensate droplet nucleation, directional transport, and efficient departure, exhibiting enhanced dew collection performance,...

Desalination by membrane distillation (MD) process has been proposed to significantly increase the water recovery ratio, especially treating with highly saline waters, e.g., seawater and shale gas wastewater. However, the state-of-the-art membranes experience severe wetting phenomenon, which generally leads to a performance decline, resulting in in...

Dew collection is a promising strategy to address the water scarcity problem in arid regions. Inspired by the natural species, engineering superhydrophilic/superhydrophobic hybrid (SSH) surfaces has received much attention for water harvesting in recent years. However, it is still challenging to design a surface that is capable of fast condensate d...

Preventing or minimizing ice formation in supercooled water is of prominent importance in many infrastructures, transportation, and cooling systems. The overall phase change heat transfer on icephobic surfaces, in general, is intentionally sacrificed to suppress the nucleation of water and ice. However, in a condensation frosting process, inhibitin...

The antimicrobial action of porous CuO microspheres (CuO), Ag nanoparticles (nAg), and bimetallic porous CuO microspheres decorated with Ag nanoparticles (CuO/nAg) was evaluated against surrogate microorganisms representative of pathogens commonly implicated in foodborne and healthcare-associated human infections. This work addressed E. coli (Esc...

Coalescence-induced condensate droplet jumping from superhydrophobic surfaces can be exploited in condensation heat-transfer enhancement, imparting self-cleaning behavior to surfaces, anti-icing coatings, and other industrial uses. An intriguing application would exploit this phenomenon to achieve thermal rectification using a sealed vapor chamber...

Most superhydrophobic surfaces undergo a wetting transition from the Cassie to the Wenzel state, either spontaneously or under the action of external perturbations. The reverse dewetting transition is hampered by a large energy barrier and in order to achieve it, external fields are usually applied. Here we perform experiments, theoretical analysis...

A significant challenge facing tissue engineers is the design and development of complex multitissue systems, including vascularized tissue-tissue interfaces. While conventional in vitro models focus on either vasculogenesis (de novo formation of blood vessels) or angiogenesis (vessels sprouting from existing vessels or endothelial monolayers), suc...

We quantitatively characterize the flow field inside organic liquid droplets evaporating on a nonwetting substrate. A mushroom-structured surface yields the desired nonwetting behavior with methanol droplets, while use of a cooled substrate (5-15 ºC) slows the rate of evaporation to enable quasi-static particle image velocimetry (PIV). Visualizatio...

The development of absorbent materials with high selectivity for oils and organic solvents is of great ecological importance for removing pollutants from contaminated water sources. We have developed a facile solution-immersion process for creating polydimethylsiloxane (PDMS)-functionalized sponges for oil-water separation. Sponge materials with de...

Coalescence-induced jumping of condensate droplets from a superhydrophobic surface with hierarchical micro/nanoscale roughness is quantitatively characterized. Experimental observations show that the condensate droplet jumping is induced by coalescence of multiple droplets of different sizes, and that the coalesced droplet trajectories typically de...

Omniphobic surfaces with reentrant microstructures have been investigated for a range of applications, but the evaporation of high- and low-surface-tension liquid droplets placed on such surfaces has not been rigorously studied. In this work, we develop a technique to fabricate omniphobic surfaces on copper substrates to allow for a systematic exam...

The development of bio-inspired interfacial materials with enhanced drop mobility that mimic the innate functionalities of nature will have significant impact on the energy, environment and global healthcare. In spite of extensive progress, the state of the art of interfacial materials have not reached the level of maturity sufficient for industria...

Engineering surfaces that sustain continuous dropwise condensation, and are composed of materials commonly employed in heat transfer applications, are of great interest for scaled-up industrial systems. We fabricate hierarchical micro/nano-structured superhydrophobic surfaces on copper substrates. Condensate droplet growth dynamics on the as-fabric...

The study of evaporation dynamics of droplets is of scientific interest and has numerous practical applications. Here, we studied the evaporation of small condensate droplets on structured surfaces with one-tier microscale roughness and two-tier micro/nanoscale roughness (the top and valley of micropillars are covered by nanograss), respectively. O...

Recent advances in condensing surfaces with hybrid architectures of superhydrophobic/hydrophilic patterns allow us to decrease the nucleation energy barrier and spatially control the water condensation. However, the condensed water is susceptible to the large pinning force of the hydrophilic area, leading to an ultimate flooding. Here, we demonstra...

Hierarchical micro/nanostructured super­hydrophobic surfaces are developed to control the nucleation, growth, and departure of condensate droplets on copper substrates. The microscale roughness elements on the hierarchical surface yield a 40% higher droplet growth rate and a 300% increase in cumulative droplet departure volume as compared to superh...

Vapor condensation plays a key role in a wide range of industrial applications including power generation, thermal management, water harvesting and desalination. Fast droplet nucleation, efficient droplet departure as well as low interfacial thermal resistance are important factors that determine the thermal performances of condensation; however, t...

Electrowetting on dielectric (EWOD) has emerged as a powerful tool to electrically manipulate tiny individual droplets in a controlled manner. Despite tremendous progress over the past two decades, current EWOD operating in ambient conditions has limited functionalities posing challenges for its applications, including electronic display, energy ge...

Despite extensive progress, current icephobic materials are limited by the breakdown of their icephobicity in the condensation frosting environment. In particular, the frost formation over the entire surface is inevitable as a result of undesired inter-droplet freezing wave propagation initiated by the sample edges. Moreover, the frost formation di...

Supplementary Information

The prospect of enhancing the condensation rate by decreasing the maximum drop departure diameter significantly below the capillary length through spontaneous drop motion has generated significant interest in condensation on superhydrophobic surfaces (SHS). The mobile coalescence leading to spontaneous drop motion was initially reported to occur on...

Evaporation of a sessile droplet is a complex, nonequilibrium phenomenon. Although evaporating droplets upon superhydrophobic surfaces have been known to exhibit distinctive evaporation modes such as a constant contact line (CCL), a constant contact angle (CCA), or both, our fundamental understanding of the effects of surface roughness on the wetti...

Evaporation of a sessile droplet is a complex, nonequilibrium phenomenon. Although evaporating droplets upon superhydrophobic surfaces have been known to exhibit distinctive evaporation modes such as a constant contact line (CCL), a constant contact angle (CCA), or both, our fundamental understanding of the effects of surface roughness on the wetti...

Composite nanoparticles have proved to be promising in a wide range of biotechnological applications. In this paper, we report on a facile method to synthesize novel Fe(3)O(4)/Au/Fe(3)O(4) nanoparticles (nanoflowers) that integrate hybrid components and surface types. We demonstrate that relative to conventional nanoparticles with core/shell config...

Engineering the dropwise condensation of water on surfaces is critical in a wide range of applications from thermal management (e.g. heat pipes, chip cooling etc.) to water harvesting technologies. Surfaces that enable both efficient droplet nucleation and droplet self‐removal (i.e. droplet departure) are essential to accomplish successful dropwise...

A surface with nanograssed micropyramidal arrays that allows for enhanced drop nucleation and departure simultaneously is successfully developed by harnessing the hierarchical roughness and heterogeneous wetting. On page 4617, Nikhil Koratkar, Shuhuai Yao, Zuankai Wang, and co‐workers show that the surface yields a global superhydrophobity as well...

Bi0.89Ti0.11FeO3 thin films with the thicknesses of 200–440 nm were fabricated on the 40-nm-thick PbZr0.2Ti0.79Nb0.01O3 (PZTN)-buffered Pt(1 1 1)/Ti/SiO2/Si substrates using a metal organic decomposition process. As a result of the good insulating property and high breakdown characteristic of the PZTN buffer layer, the leakage currents in the Bi0.8...

The 150-nm-thick Ce:Bi2Ti2O7 (Ce:BTO) thin films have been grown directly on p-type Si (100) substrate by a metal organic decomposition method. The effect of different crystallization routes on the structure and electrical properties of the films has been investigated. X-ray diffraction patterns show that phase-pure pyrochlore Ce:BTO films can be o...

Polycrystalline BiFeO3 and Bi1−xTbxFeO3 (BTFO) (x=0.05–0.16) thin films were deposited on indium tin oxide/glass substrates via a metal organic deposition method. The influence of Tb doping content on the structure and multiferroic properties was investigated. X-ray diffraction results reveal that there may exist a structure transition around x=0.1...

BiFeO3 (BFO) thin films deposited on various thicknesses (0, 40, 80, and 160 nm) of Bi3.5Nd0.5Ti3O12 (BNT) buffer layers were fabricated on indium tin oxide (ITO)/Si substrates using a metal organic decomposition process. X-ray diffraction (XRD) measurements reveal that the BNT buffer layers can favor the growth of (110)-oriented grains in the BFO...

The BiFe1 − xMnxO3 (BFMO) (x = 0.03, 0.05 and 0.07) thin films were deposited on indium tin oxide/glass substrates using a metal organic decomposition method. X-ray diffraction analysis reveals that the structure of BiFeO3 films is distorted somewhat by Mn substitution. The leakage measurements indicate that Mn doping content is a dominant factor a...

A (124)-oriented SrBi4Ti4O15 (SBTi) ferroelectric thin film with high volume fraction of \(\alpha^{\rm SBTi}_{(124)}=97\%\) was obtained using a metal organic decomposition process on SiO2/Si substrate coated by (110)-oriented LaNiO3 (LNO) thin film. The remanent polarization (P r) and coercive field (E c) for (124)-oriented SBTi film are 12.1 μC/c...

Bi _0.97 La _0.03 FeO ₃ (BLFO) films were prepared using the metal organic decomposition method on indium tin oxide (ITO)/glass substrates. Ferroelectric properties, morphologies and leakage currents of BLFO thin fims are very sensitive to the annealing temperature. The content of grain boundaries in the films is cons...

BiFeO3 (BFO) films with and without a Bi3.5Nd0.5Ti3O12 (BNT) buffer layer were fabricated on indium tin oxide (ITO)/Si substrates using a metal organic decomposition process. X-ray diffraction measurements reveal that a BNT buffer layer can favour the growth of (1 1 0)-oriented grains in the BFO film. BFO film with a BNT buffer layer exhibits well...