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Performance enhancement of graphene-coated micro heat pipes for light-emitting diode cooling
摘要： The rate of water transport through graphene nanocapillaries is profoundly enhanced compared to that in microscale capillaries due to the prevalence of exceptionally high capillary pressures and large slip lengths. As an inaugural study, we integrate graphene nanocapillaries into a micro heat pipe (MHP) for enhanced light-emitting diode (LED) cooling. With the use of graphene nanocapillaries, the ultrafast water transport synergically enhances the water circulation and evaporation process in the microfluidic device. The graphene-coated MHP achieves more than 45% enhancement in the overall performance compared to the uncoated counterpart. In turn, the experiments demonstrate a drastic reduction of LED’s operating temperature (more than 25 °C) which translates into a significantly prolonged lifespan of LED. The molecular dynamics simulations reveal that the oxygenated functional groups attached on graphene further increase the capillary pressure (~1000 bar) and effective velocity (~20 m/s) of the nanoconfined water, compared to those (~500 bar and ~10 m/s) in a pristine graphene nanochannel. The ultrafast water transport in graphene nanocapillary is justified. This study provides a holistic analysis and important insight into the phenomenon of ultrafast water transport in graphene nanocapillaries that exhibits an enormous potential in thermal energy management applications for LED cooling.
关键词： Electronics cooling,Micro heat pipe,Graphene nanocapillaries,Ultrafast water transport
更新于2025-09-23 15:19:57
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Laser Direct Structuring of Bioinspired Spine with Backward Microbarbs and Hierarchical Microchannels for Ultrafast Water Transport and Efficient Fog Harvesting
摘要： Achieving effective dropwise capture and ultrafast water transport is essential for fog harvesting. In nature, Cactus uses the conical spine with micro-barbs to effectively capture fog while Sarracenia utilizes the trichome with hierarchical microchannels to quickly transport water. Herein, we combined their advantages to present a novel configuration, spine with barbs and hierarchical channels (SBHC), for simultaneous ultrafast water transport and high-efficient fog harvesting. This bio-inspired SBHC exhibited the fastest water transport ability and the highest fog harvesting efficiency in comparison with spine with hierarchical channels (SHC), spine with barbs and grooves (SBG) and spine with barbs (SB). Based on the fundamental SBHC unit, we further designed and fabricated a 2D spider-web alike fog collector and a 3D cactus alike fog collector using direct laser structuring and Origami techniques. The 2D spider-web and 3D cactus alike fog collectors showed high-efficient fog collection capacity. We envision that this fundamental understanding and rational design strategy can be applied in fog harvesting, heat transfer, liquid manipulation, and microfluidics.
关键词： Direct laser structuring,Water transport,Spine and micro-barbs,Fog harvesting,Hierarchical microchannels
更新于2025-09-23 15:19:57
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Mass Accommodation Coefficients of Water on Organics from Complementary Photoacoustic and Light Scattering Measurements on Laser-Trapped Droplets
摘要： The mass accommodation coefficient, αM, describes the liquid?vapor evaporation and condensation kinetics at interface. In spite of numerous experimental efforts, reliable values of αM are still not available for many substances. Here, we present a novel experimental technique, photothermal single-particle spectroscopy (PSPS), that allows for a robust retrieval of mass accommodation coefficients from three simultaneous independent measurements. PSPS combines resonant photoacoustic absorption spectroscopy with modulated Mie scattering measurements on single particles. We study the mass transport of water on organic aerosol droplets that are optically trapped using counter-propagating tweezers. We find the mass accommodation coefficient of water on a pure model organic that is fully miscible with water to be 0.021 at 296 K and to decrease by more than an order of magnitude when the temperature increases to 309 K. The experimentally observed temperature dependence of αM shows an Arrhenius behavior. Furthermore, the water content of the droplets is found to have a profound effect on αM is observed at low water concentrations, while at elevated water concentrations, we observe a 5-fold increase in αM. The technique presented in this work has the potential to become a reliable method for the retrieval of αM values at liquid?vapor interfaces, which are essential for accurate global climate and pharmaceutical aerosol inhalation modeling, to mention but a few.
关键词： temperature dependence,photoacoustic absorption spectroscopy,optical trapping,water transport,organic aerosol droplets,modulated Mie scattering,mass accommodation coefficient,Arrhenius behavior,PSPS,photothermal single-particle spectroscopy
更新于2025-09-23 15:19:57
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<i>(Invited)</i> Water Transport Along Si/Si Direct Wafer Bonding Interfaces
摘要： The transport of water in a highly confined gap made by the direct bonding of low roughness silicon hydrophilic wafers is studied. We derive the equation for the transport of water from chemical potential gradients, using Stokes and conservation equations. The transport equation is found to be a Porous Medium Equation with exponent 2. A solution for this equation with stepwise boundary conditions is given. The model is tested against different initial conditions for inward and outward flow, and different temperatures and humidity levels.
关键词： silicon direct bonding,chemical potential gradients,Porous Medium Equation,water transport,hydrophilic wafers
更新于2025-09-10 09:29:36