Capillary Wicking Research Articles

The synergistic effect of micro/nanostructure length scale and fluid thermophysical properties on pool boiling heat transfer

Facile surface micro/nanostructuring techniques for additively-manufactured (AM) aluminum alloy (AlSi10Mg) have recently been developed. The structuring techniques are not only highly scalable, but they also enable the tailoring of structure length scale and morphology to enhance the pool boiling heat transfer coefficient. Our past study revealed that the structure cavity size of 5 µm is favorable for bubble nucleation during pool boiling of dielectric fluid, HFE-7100, resulting in significant enhancements in the heat transfer coefficients (h). However, owing to the differences in thermophysical properties between different coolant fluids, including saturation temperature, latent heat of vaporization and surface tension, the required structure size range for bubble nucleation and capillary wicking force for liquid re-supply are expected to differ significantly. To explore the effect of structure length scale on the pool boiling performance of coolants with different thermophysical properties, this work develops a new surface structuring technique consisting of a dual-stage metallurgic heat treatment process and single-stage crystallographic etching process to tune the structure length scale across nearly two orders of magnitude, viz., from 0.3 μm to 15 μm. Using coolant media of vastly different thermophysical properties, i.e., dielectric fluid HFE-7100 and deionized water, we show that while microcavities with sizes ranging from 3 to 8 μm are favorable bubble nucleation sites for boiling of HFE7100, which results in the enhancement of the maximum heat transfer coefficient (hmax) by 83.4 to 103.8 % as compared to a conventional plain Al6061 surface, larger microcavity sizes of 10 to 15 μm are required to effectively promote bubble nucleation of water. This large microcavity size range of 10 to 15 μm, produced through rational nanoparticle agglomeration of the rich Si-phase in AM AlSi10Mg in elevated temperature, followed by an indirect removal process using a chemical process, is found to significantly increase hmax of water by up to 259.9 % as compared to conventional nanostructures formed on Al6061. In addition, the new AM structured surfaces also exhibit up to 26.6 % enhancement in critical heat flux (CHF) as compared to highly-wicking conventional nanostructured Al6061. In summary, by utilizing scalable fabrication techniques to tailor the structure length scale on AM AlSi10Mg, this work not only reveals the favorable microcavity sizes for bubble nucleation of different coolant fluids to enhance boiling, but also provides useful micro/nanostructure design guidelines that can be adopted to enhance boiling of other coolants and phase change applications.

Enhancement of critical current density using micro-porous structure in a low-temperature water electrolysis

The critical current density (CCD), which limits the hydrogen production rate was measured by forming micro-porous structures on the cathode electrode in a low-temperature water electrolysis. Several micro-porous structures were formed by the electrodeposition method varying the current density during the deposition. A maximum 54% enhancement of the CCD was recorded compared to the plain surface. With the micro-porous structures, the superior capillary wicking effect allowed the electrolyte to penetrate the structure, resulting in the increased number of hydrogen nucleation sites. The increased hydrogen nucleation sites led to the decreased hydrogen bubble size and increased departed bubble density, which delayed formation of the hydrogen film leading to the CCD. The surface morphology revealed that the multiple pore layers with the interconnected pores exhibited superior capillary wicking effect compared to the open type single pore layer. It is expected that the results of present work stimulate further research regarding electrode surface design in the low-temperature water electrolysis.

Influence of the surface energy of a basalt fiber on capillary wicking and in-plane permeability of reinforcements

This study evaluates the influence of a thermal treatment of a basalt fiber on capillary wicking tests and in-plane permeability experiments, under several pressure differences. The impact of the treatment was characterized at three scales: microscopic, to determine the fiber surface energy; mesoscopic, to estimate an equivalent capillary pressure (Pcap) of the fabric in spontaneous impregnation; and macroscopic, to determine the saturated (Ksat) and unsaturated (Kunsat) permeability of the fibrous preform at the process scale. Results at the microscopic scale showed that the thermal treatment increased the polarity of the fiber by 22% and decreased its surface roughness. Capillary wicking tests showed that the treated fabric presents a better affinity with water, increasing Pcap by 68%. At the process scale, permeability experiments showed the increase of Ksat and Kunsat after treatment. Finally, results of capillary pressure (ΔPγ) showed a dominance of capillary effects under the negative pressure difference.

The start-up characteristics of a novel loop heat pipe with stainless steel capillary wick

Loop heat pipe (LHP) is an advanced thermal management technology that utilizes liquid–vapor phase change and capillary action to achieve efficient heat transfer across long distances and in various directions. The start-up of an LHP is crucial for its reliable and stable operation. This study aims to explore the start-up characteristics and temperature variations of various components under different heating conditions by designing a cost-effective flat plate evaporator LHP with a stainless-steel casing and acetone as the working fluid. The experimental analysis examined the performance of the LHP under varying heating powers from 28 to 60 W, positions, and gravity angles. The findings revealed that the LHP successfully started at 28 W, and a temperature overshoot occured when the heating position was near the compensation chamber. Notably, the start-up time was 400 s faster compared to the heating condition near the mean pressure chamber. When the evaporator was tilted such that the compensation chamber was above the evaporator’s pressure equalization chamber, circulation within the LHP could not be established. The thermal resistance of the LHP decreased with increasing heating power, achieving a maximum reduction of 51.51 %. When both the compensation chamber and the mean pressure chamber were heated simultaneously, the impact of the gravity inclination angle on thermal resistance was minimized. This study introduces an innovative capillary wick LHP with high start-up success rates and cost-effectiveness, providing both empirical data and theoretical insights for the refinement and optimization of civilian LHP designs.

Surface structures and wettability: Their roles in enhancing nucleate boiling heat transfer of refrigerants

Nucleate boiling is an effective heat transfer mechanism. Previous studies have demonstrated that modifying surface structure or wettability can independently improve nucleate boiling efficiency; however, the combined effects and optimal modification sequence remain underexplored. This research aims to comprehensively analyze the influence of surface structure and wettability on the nucleate boiling heat transfer performance of refrigerants. Different surface structures and wettability were prepared using surface polishing, laser ablation, mechanical cutting, and a combination that involved initially employing laser ablation, followed by the application of chemical etching, and finishing with the treatment using materials possessing low surface energy. The static contact angles on these surfaces were measured via the capillary rise method, followed by pool boiling experiments and bubble behavior visualization. The results show that increasing surface wettability can enhance bubble departure frequency and capillary wicking, thereby improving critical heat flux and heat transfer coefficient. The key to optimizing surface modification to enhance critical heat flux involves constructing alternating high and low nucleation core regions to reduce interactions between bubbles; for enhancing heat transfer coefficient, the key lies in constructing compact nanoscale structures that expand the heat transfer and nucleation area, followed by improving wettability.

Experimental study on Start-Up and heat transfer characteristics in loop heat pipes with dual heat sources for battery thermal management system

Electric vehicles represent a breakthrough in sustainable transportation, significantly diminishing global emissions. The efficacy of lithium-ion batteries is significantly influenced by the operating temperature, with elevated temperatures potentially resulting in thermal runaway. A proficient battery thermal management system (TMS) must resolve this concern and uphold safe temperatures. Loop heat pipes (LHPs) offer passive cooling technology and have garnered the attention of researchers. Nonetheless, research on LHPs for battery thermal management systems is scarce, and prior investigations have concentrated on a singular heat source. A liquid heat pipe with a dual heat source evaporator has been engineered to simulate the battery arrangement of electric vehicles, which typically comprises multiple battery cells. This study seeks to examine the starting and heat transmission characteristics of LHP. Two battery simulators are fabricated from steel blocks equipped with cartridge heaters. A copper evaporator (121 × 56 × 20 mm) is equipped with a stainless-steel screen mesh capillary wick, and thermocouples are linked to a National Instruments data acquisition (NI DAQ) system for the LHP. Ethanol serves as the working fluid at a filling ratio of 60 %. The startup characteristics of the LHP are examined by altering the heat load, coolant flow rate, and coolant temperature. The experimental findings indicate that the LHP effectively initiates operation at heat loads ranging from 20 to 100 W. The LHP with multiple heat sources demonstrates reduced temperatures compared to a single heat source. The best performance of coolant flow rate and temperature for the quickest startup times are 1.5 L/min and 25 °C, respectively. The lowest thermal resistance achieved is 0.17 °C/W.

Assessing the Durability, Mechanical, and Microstructural Properties of Nanosilica-enhanced Coconut Shell Concrete: A Sustainable Approach

This study explores the properties of concrete as a sustainable substitute for cement through the use of nanosilica in an eco-friendly aggregate system. Daily life generates a larger amount of coconut shell waste from the tropical zone. In India, the yearly deposition of coconut shell is about 80,000 tonnes, which is 6.7% of total agricultural waste. Crushing gravel production emits CO2, which is an environmental concern. Simultaneously, to diminish waste disposal of coconut shell can be effectively utilised as coarse aggregate in lightweight concrete. The conventional concrete (CC) was fully replaced by coconut shell coarse aggregate and crushed gravel sand (Msand) as fine aggregate in plain Portland cement. Nanosilica replaces cement in the conventional blend at 0%, 1%, 2%, 3%, and 4%. This study describes the concrete's hardened properties, such as compressive strength, splitting tensile strength, and flexural strength. Among all the mechanical performances, the N2 blend is significant. The N2 mix exhibits a trend that aligns with the correlation between compressive strength and splitting tensile strength. The transport durability performance related to capillary wick action of the optimum blend (N2 mix) has 0.018 mm/min0.5. The pore filler mechanism and pozzolanicity of 2% NS is more synergic than other combinations. The N2 mix in H2SO4 environment has less mass and strength loss. The N2 blend's morphology is robust relative to the CC mix because of the secondary C-S-H gel and homogeneous, smooth hydrated grain. As a result, the report concludes that using coconut shell as an aggregate in concrete can reduce waste disposal in landfills, while using nanosilica in place of cement can reduce CO2 emissions.

Experimental investigation on the thermal performance of a large-size aluminum vapor chamber for multi-point heat sources

Abstract With the development of electronic information technology, the integration and power of electronic equipment continue to increase. As an efficient heat transfer element, vapor chambers are widely used in the field of heat dissipation of electronic devices. However, greater challenges have been posed in terms of higher heat dissipation capacity, larger size, and lighter weight. Therefore, a large-scale aluminum vapor chamber with a size of 340 mm×295 mm ×7.5 mm is designed for the heat dissipation of multi-point array heat sources. Multiple parallel porous ribs are sintered to form capillary wicking channels and vapor diffusion paths, which efficiently transfer the heat from the middle of the vapor chamber to the cold plate on the two sides. The transient working characteristics and heat dissipation performance under different working conditions are experimentally investigated. The results show that there is obvious temperature instability, which can be suppressed by the tilt of the vapor chamber and the increase of the heating power. Under the tilt condition, the temperature rises in the vertical direction due to the influence of gravity, while the inclination angle has basically no effect. The vapor chamber can work stably at the total heating power of 2100 W with the smallest thermal resistance 0.03 °C/W. The single-point heat flux can reach 7.3W/cm2 for the 128 heat sources. Compared to a traditional vapor chamber, the proposed aluminum vapor chamber provides a thermal management solution for large-size electronic devices with multiple heat sources.

Thermal distillation of hypersaline waters toward zero liquid discharge via spontaneously siphon-channeling crystallized salt

Membrane distillation of hypersaline solution with low-grade waste heat is particularly outstanding to address the challenge of water-energy nexus. However, the high causticity of hypersaline solution always makes this system complicated and expensive. Here, we design a passive membrane-free thermal distiller for hypersaline desalination with high stability, easy operation and low cost. A siphon channel is constructed with the capillary wick and the crystallized salt, which can self-flush the crystallized salt and assure the stability of this passive system. Together with optimizing heat transfer process to suppress temperature polarization, the integrated distiller system can efficiently collect water and salt, achieving zero liquid discharge. The system can stably desalinate 70 g/L NaCl solution, with the water yield of 1.33 kg m−2h−1 and salt collection of about 0.34 kg m−2h−1 at 60 °C. This passive system is expected to desalinate hypersaline water in large-scale commercial production, for example, integrating with desalination industry.

Performance Analysis of Water Heat Pipe for Application of the Passive Cooling System in Nuclear Power Plants

Incorporating heat pipes into passive cooling systems in nuclear reactors offers the benefits of passive operation without external power, a simple design, and high thermal capacity. Accurate thermal performance prediction of the heat pipe is crucial for ensuring safe reactor design and operation. Prior studies on nuclear reactor systems utilizing heat pipes have focused on thermosyphons, which operate by gravity. However, to expand the range of heat pipe applications in reactor systems, experimental investigations of large-scale heat pipes driven by capillary pumping force are required. In this study, a water heat pipe with a 25.4-mm diameter and 4-m length was manufactured to provide thermal experimental results under extreme conditions, such as system rollover or loss-of-cooling accidents. A three-dimensional (3D) printing technique was used to fabricate the high-performance lattice capillary wick structure by combining cubic and diamond lattice structures. The 3D printed wick structure showed 21 to 165 times higher capillarity and enhanced surface properties compared to the screen mesh wick structure. Compared to wickless thermosyphons, the 3D printed wick heat pipe exhibited higher thermal conductivity, stable operation in both vertical and horizontal orientations, and faster startup under extreme conditions.

Effect of tilt angle and base plate design on the performance of a loop heat pipe driven by vapor–liquid injector

With the rapid development of microelectronics technology and the increasing heat flux of electronic devices, loop heat pipes have garnered significant attention for their highly efficient passive heat transfer performance. However, the heat transfer performance of conventional loop heat pipes is impaired by the heat leakage, and the maximum heat flux is unable to meet the heat dissipation requirement of high-heat-flux devices. To solve this problem, a loop heat pipe with a vapor-driven injector (LHPI) was previously proposed. However, only the heat transfer performance of the horizontally-placed LHPI had been investigated in the preliminary stage, and the effect of gravity on the heat transfer performance was not further discussed. Now in this paper, a 360° rotatable experimental bench is designed to investigate the influence of the tilt angle on the performance of LHPI. In addition, a capillary wick is integrally sintered with the trough baseplate and the microcolumn baseplate of the LHPI, respectively, to reduce the thermal resistance between them. The results show that the heat transfer performance of LHPI is significantly affected by its tilt angle. In the horizontal condition, LHPI exhibits the lowest baseplate temperature and thermal resistance, and the best heat transfer performance, which verifies its applications in engineering. Integral sintering increases the maximum thermal load from 300 W to 350 W under stable operation conditions of LHPI. The maximum thermal load of the integrated micro pin-finned baseplate reaches 500 W, which improves the heat dissipation effect by 42 % in heat dissipation compared to the trough baseplate under the same conditions., providing an improvement angle for the traditional LHP.

Thermal dynamics aspect identification of loop heat pipe with capillary tube wick using nonlinear autoregressive exogenous neural network

The loop heat pipe (LHP) has the potential to be used as a passive cooling system in small modular reactors. The research objective is to study the thermal dynamics of LHP with capillary tube wick using a non-linear autoregressive exogenous (NARX) based on a neural network. The neural network identification of LHP with capillary tube wick was carried out on the MATLAB platform. The experiment data obtained is used to identify the neural network of LHP with capillary tube wick. The temperature of the water as an evaporator heat source was varied at 60, 70, 80, and 90 °C. The LHP was charged with demineralized water with a filling ratio of 100 %. The air as a coolant in condenser section was blown at velocity of 2.5 m/s. The LHP was vacuumed with an initial pressure of 2690 Pa. The result confirmed that NARX based on the neural network model can predict the temperature of the condenser section with a given input set under the steady-state and transient conditions. The coefficient of determination is higher than 0.998 and Mean Square Error (MSE) is below 0.0082. The result obtained shows that the NARX neural network model can predict thermal dynamics phenomena in LHP quickly and precisely.

Novel capillary rise enhancement of dual-shape hybrid groove made by laser etch-sputtering

High aspect ratio groove is attractive in varied applications, but is not easy to fabricated in practice. A dual-shape hybrid groove (DSHG), with a novel capillary wicking performance, was simply fabricated using laser etch-sputtering method on aluminum sheet. Except for the high aspect ratio grooves, outer super-hydrophilic grooves covered with micro/nano multi-scale structures were also sputtered by pulsed laser in the simultaneous processing of DSHG. It was found that the combination of high capillary pressure and high permeability of DSHG, as well as the fluid interaction within the dual structure, contributes to improving capillary transport. Consequently, the capillary rise of DSHG reached 200 mm in just 85 s, with an average speed of 24 mm/s within the first 2 s. The rectangle flow defined in the rectangle groove, along with the bulk flow and corner flow in the tapered groove, can establish the capillary dynamics equations for DSHG. The laser etch-sputtering of DSHG presents a promising approach in mass production of liquid capillary devices.

High-Performance Bioinspired Hierarchical Microgroove Wick for Ceramic Vapor Chambers Achieved by Nanosecond Pulsed Lasers.

Directly integrating ceramic vapor chambers into the insulating substrate of semiconductor power devices is an effective approach to solve the problem of heat dissipation. Microgrooves that could be machined directly on the shell plate without contact thermal resistance and mechanical dislocation offer exciting opportunities to achieve high-performance ceramic vapor chambers. In this study, a bioinspired hierarchical microgroove wick (BHMW) containing low ribs via one-step nanosecond pulsed laser processing was developed, as inspired by the Sarracenia trichome. The superwicking behavior of microgrooves with different structural parameters was investigated using capillary rise tests and droplet-spreading experiments. The BHMW exhibited excellent capillary performance and anisotropic hemiwicking performance. At a laser scanning spacing of 30 μm, the BHMW achieved a capillary wicking height of 114 mm within 20 s. The optimized BHMW demonstrated a capillary parameter (ΔPc·K) and an anisotropic hemiwicking ratio of 4.46 × 10-7 N and 11.93, respectively, which were 1182 and 946% higher than references, as achieved through nanosecond pulsed laser texturing under identical parameters. This work not only develops a high-performance hierarchical alumina microgroove wick structure but also outlines design guidelines for high-performance ceramic vapor chambers for thermal management in semiconductor power devices.

Enhanced Pool Boiling Heat Transfer with Porous Ti-6Al-4V-Coatings Produced by Cold Spray Metal Additive Manufacturing

In advancing industrial heat transfer mechanisms, surface coatings offer significant potential. This research elucidates the efficacy of the metal additive manufacturing Cold Spray deposition technique for producing enhanced boiling surfaces, specifically focusing on Ti-6Al-4V (Ti64) coatings on Aluminium substrates. This offers a rapid and low-cost fabrication method for producing lightweight enhanced boiling surfaces. The Cold Spray method is typically used to create dense metal deposits. Here, the process has been specially tuned to create highly inhomogeneous honeycomb-type porous Ti64 coatings. Critical Cold Spray deposition parameters, such as particle velocity, preheat temperature, and deposition rate have been identified to create repeatable porous coatings, with thicknesses of up to 3.0 mm achievable. Following deposition, several samples were subjected to systematic boiling heat transfer tests in a purpose-built pool boiling apparatus. Boiling curves were generated for the augmented Cold Spray surfaces as well as a bare surface, with the latter acting as a baseline to which enhancement levels were assessed. Initial data analysis shows that some of the tested surfaces exhibit a notable increase in boiling heat transfer coefficient and Critical Heat Flux (CHF). This enhancement is potentially attributed to increased surface area, increased nucleation site density, capillary wicking, and mitigation of lateral bubble coalescence, though excessive coating thickness may degrade heat transfer. In summary, the novel Ti64 surface structures developed using the Cold Spray deposition technique exhibits high potential for industries necessitating superior boiling heat transfer performance. Importantly, the manufacturing process is industrially scalable, offering the capacity to rapidly coat large areas at low cost compared with subtractive manufacturing other metal additive manufacturing methods.

Experimental investigation of thermal characteristics on a new loop pipe model for passive cooling system

The heat pipes have the potential to be used as a passive cooling system (PCS) in thermal installations including nuclear facilities. In that context, this experimental study is correlated with the research on the new type of Loop Heat Pipe (LHP) as the PCS. This work aimed to study the characteristics of LHP with capillary pipe wick. The experiments involved varying the pool water temperature as evaporator heat load at 35, 45, 55, and 65 °C, filling ratio charged at 20, 40, 60, 80, and 100 % of LHP evaporator volume, and the flow air velocity to the fins in the condenser at 0, 1, 1.5, 2, and 2.5 m/s. The LHP was operated in sub-atmospheric conditions with an initial pressure of 2666.4 Pa. The results show that LHP has a stable two-phase natural circulation under all variations of heat loads, filling ratios, and air velocities tested. The results also show that display excellent thermal performance with the lowest thermal resistance of 0.0524 ± 0.0004 °C/W operating at the highest water temperature source, the highest filling ratio, and the highest air velocity. It is concluded that the LHP model with capillary pipe wick has similar thermal characteristics to other types of heat pipes. This wick function effectively in preventing vapor flow from the evaporator toward the condenser, and otherwise it can facilitate as condensate path from the condenser to evaporator. The stable two-phase natural circulation stability analysis showed that the LHP with capillary wick has very good thermal performance as heat absorber and heat releaser.

Study on the flow characteristics of microscale copper inverse opal wick structures

Ultra-thin heat pipes are extensively used to address heat dissipation challenges in compact electronic devices with limited space. Research on new types of micro-porous wick is crucial for enhancing the heat transfer of ultra-thin heat pipes. The hydraulic transport properties of micro-porous wick structures are crucial factors for the applications. The inverse opal (IO) micro-porous metal structure has gained extensive attention for its ordered periodic arrangement and high porosity characteristics. In the paper, the copper inverse opal (CIO) and gradient CIO are fabricated by a template-assisted deposition method. Experimental measurements are conducted to study the fluid ascent process within the CIO structure. In addition, a face-centered cubic geometric model is established based on the structure information obtained by a scanning electron microscope (SEM). The calculation employs a porous media model and takes into account the resistance characteristics in the initial phase. The relative error between the simulation and experimental results is less than 7.7%. Furthermore, the fabricated gradient CIO structure is uniform and exhibits a higher permeability than single-pore CIO. The permeability of this gradient CIO is about 1.9–3.2 × 10−14 m2. Understanding the microscopic liquid transport process within CIO structures is of great importance in the selection and optimization of capillary wick structures.

Hydrovoltaic electricity generator using a hierarchical NiFe LDH-coated CuO nanowire mesh device

Innovative advancements in sustainable water-energy nexus solutions are paramount in the current global context. This study introduces a hydrovoltaic electricity generator with advanced capillary wicking under ambient conditions. A hierarchical nanostructure of nickel–iron layered double hydroxides (NiFe LDHs) was deposited on copper oxide nanowires (CuO NWs) on Cu meshes to enhance the diffusion of ion-rich water. The LDH coating improves the overall power, voltage, and robustness of the device. A 200 µL droplet of hygroscopic solutions on a device produces electricity at 0.2 V scale, one of which could be sustained for over 140 h. We explored the working mechanisms, parametric studies, and potential scalability through serial allocation for further applications. This study allows water-driven electricity generation using hierarchical nanostructured materials, effectively harnessing renewable energy from readily available hygroscopic salts or abundant seawater resources.

Capillary Wicking on Heliamphora minor-Mimicking Mesoscopic Trichomes Array.

Liquid spontaneously spreads on rough lyophilic surfaces, and this is driven by capillarity and defined as capillary wicking. Extensive studies on microtextured surfaces have been applied to microfluidics and their corresponding manufacturing. However, the imbibition at mesoscale roughness has seldom been studied due to lacking fabrication techniques. Inspired by the South American pitcher plant Heliamphora minor, which wicks water on its pubescent inside wall for lubrication and drainage, we implemented 3D printing to fabricate a mimetic mesoscopic trichomes array and investigated the high-flux capillary wicking process. Unlike a uniformly thick climbing film on a microtextured surface, the interval filling of millimeter-long and submillimeter-pitched trichomes creates a film of non-uniform thickness. Different from the viscous dissipation that dominated the spreading on microtextured surfaces, we unveiled an inertia-dominated transition regime with mesoscopic wicking dynamics and constructed a scaling law such that the height grows to 2/3 the power of time for various conditions. Finally, we examined the mass transportation inside the non-uniformly thick film, mimicking a plant nutrition supply method, and realized an open system siphon in the film, with the flux saturation condition experimentally determined. This work explores capillary wicking in mesoscopic structures and has potential applications in the design of low-cost high-flux open fluidics.

Gradient-Pattern Micro-Grooved Wicks Fabricated by the Ultraviolet Nanosecond Laser Method and Their Enhanced Capillary Performance.

Capillary-gradient wicks can achieve fast or directional liquid transport, but they face fabrication challenges by traditional methods in terms of precise patterns. Laser processing is a potential solution due to its high pattern accuracy, but there are a few studies on laser-processed capillary-gradient wicks. In this paper, capillary step-gradient micro-grooved wicks (CSMWs) were fabricated by an ultraviolet nanosecond pulsed laser, and their capillary performance was studied experimentally. The CSMWs could be divided into three regions with a decreasing capillary radius. The equilibrium rising height of the CSMWs was enhanced by 124% compared to the non-gradient parallel wick. Different from the classical Lucas-Washburn model describing a uniform non-gradient wick, secondary capillary acceleration was observed in the negative gradient direction of the CSMWs. With the increase in laser power and the decrease in scanning speed, the capillary performance was promoted, and the optimal laser processing parameters were 4 W-10 mm/s. The laser-enhanced capillary performance was attributed to the improved hydrophilicity and reduced capillary radius, which resulted from the increased surface roughness, protrusion morphology, and deep-narrow V-shaped grooves induced by the high energy density of the laser. Our study demonstrates that ultraviolet pulsed laser processing is a highly efficient and low-cost method for fabricating high-performance capillary gradient wicks.