Wick Structure Research Articles

3D printed aluminum flat heat pipes with micro grooves for efficient thermal management of high power LEDs

As the electronic technology becomes increasingly integrated and miniaturized, thermal management has become a major challenge for electronic device applications. A heat pipe is a highly efficient two-phase heat transfer device. Due to its simple structure, high thermal conductivity and good temperature uniformity, it has been used in many different industrial fields. A novel aluminum flat heat pipe, with micro-grooves, has in the present work been designed and fabricated by using a 3D printing technology. Aluminum powder was used as a raw material, which was selectively melted and solidified to form the shape of the heat pipe. The sintered aluminum powder increased the roughness of the inner surface of the heat pipe, and the designed micro-grooves further enhanced the capillary forces induced by the wick structure. The wettability, for the working fluid (acetone), was excellent and the capillary forces were sufficient for the working fluid to flow back in the pipe. The effects of working fluid filling ratio, on the heat transfer performance of the heat pipe, was also investigated. It was shown that a filling ratio of 10% gave the best heat transfer performance with the lowest thermal resistance. The 3D-printed flat heat pipe was, therefore, also tested for the thermal management of a LED. The temperature of the LED could be kept within 40 °C and its service life became prolonged.

Research progress on performance enhancement of heat pipes: a review

Heat pipes are silent heat transfer devices that work on the motion of boiling and condensation process. They have been used in space crafts, heat recovery and ventilation, power conversion, energy, and electronics cooling applications. Over the past few eras, several necessary upgradations in heat pipe technologies have happened to implement new advanced fluids, design modification, and modified wick structures. Heat transfer enhancement due to these upgradations/implementations has been deliberated in many studies. In this paper, performance studies of heat pipes with deposition of nanoparticles and suitable coating made on the wick structure are reviewed. Various heat transfer mechanisms involved in heat pipes with nanoparticles deposition on the evaporator are summarized. Also, the various heat transfer mechanisms in heat pipes while using a nanofluid and a porous coating in the evaporator are summarized. This review shall offer a superior comprehension of the improvement required in cooling devices and help future research fraternity to develop advanced cooling gadgets.

Advanced Micro-/Nanostructured Wicks for Passive Phase-Change Cooling Systems

ABSTRACT Heat pipes and vapor chambers have been widely utilized for the thermal management of electronic devices due to their effective heat transport, passive cooling operation, and high reliability. In these devices, a wick structure transports a working fluid from the heat sink to the heat source via capillary action in the wick structure. This paper provides a broad overview of the latest studies on the development of Micro-/Nanostructured wicks for passive cooling systems. Micro/nanopillar-based wick structures provide a high capillary pressure, a large permeability, and larger areas for evaporation, resulting in a significantly higher heat removal capability and dryout heat flux. A special emphasis is placed on the various types and geometries of wick structures and their performance. Additionally, limitations and recommendations for future investigations are discussed.

Phase-change heat transfer of bare surface evaporator with phase-separating wick in downward facing orientation

Liquid-vapor, phase-change heat transfer using wicks can provide reliable and high heat flux cooling capability, especially in microgravity applications. However, the maximum heat removal capacity, also known as Critical Heat Flux (CHF), is related to the capillary-driven liquid supply limit and/or vapor removal limit. A key is to develop a novel wick structure, offering efficient liquid supply as well as vapor removal pathways. In this study, the Bare Surface Evaporator with Phase-Separating Wick (BEPSW) is examined to understand the liquid supply and vapor removal limits in a downward facing orientation for microgravity environment. The BEPSW consists of a bare surface evaporator for the efficient evaporation, and the distributed, sintered-particle post wicks with the phase-separating wick for enhanced liquid supply and vapor removal. The bare surface is fabricated from a copper disk 19.1 mm in diameter, while the post and phase-separating wicks are manufactured using 10 and 3 layers of sintered copper particles, respectively. The heat flux is measured as a function of the surface superheat for different post-post pitch distances (Lp = 2.5, 3.5, 4.5, and 7 mm) and average particle sizes (<dp> = 350 and 550 μm), using distilled water as a working fluid. The results show that the CHF increases as the pitch distance decreases from Lp = 7 to 3.5 mm in both particle sizes due to the increased liquid supply through the post wicks, while it decreases below Lp = 2.5 mm in both particle sizes due to the liquid entrainment limit, i.e., the maximum CHF is observed at Lp = 2.5 to 3.5 mm. The measured maximum CHF and Heat Transfer Coefficient (HTC) with 350 μm particle size is 184 W/cm2 (24.9°C superheat) and 7.7 W/cm2-K (144 W/cm2 heat flux), respectively, and 207 W/cm2 (44.3°C superheat) and 5.4 W/cm2-K (118 W/cm2 heat flux) for the 550 μm particle size, both at Lp = 3.5 mm. The CHF models, both the capillary-viscous and entrainment limits, predict the optimal particle size, showing that it increases with increasing pitch distance of the post wicks at given post wick geometries. This is related to the type of limitation that controls the CHF, i.e., either capillary-viscous limit or the entrainment limit. Also, the results show that the CHF using the 550 μm wick exceeds that of 350 μm at given pitch distance, due to the large liquid permeability.

Analysis of the optimum configuration for the capillary rise and the permeability of the fiber wick structure for heat removal in heat pipes

The condensed working fluid inside a heat pipe is pumped from the condenser to the evaporator section to complete the operating cycle by using the capillary force generated inside the wick structure. Since the miniature heat pipes have smaller vapor cross-sectional area, the fiber wick structure is suitable for this application. The fiber wick structure can be designed to provide an excellent flow path for the working fluid with an optimum configuration based on a hexagonal fiber arrangement. By a microscopic investigation of the wick structure, the porosity can be related with the physical properties, effective pore radius and the capillary pressure. The effective pore radius and the capillary pressure are important parameters to characterize the permeability because it enables one to predict the flow rate obtainable under a given pressure drop necessary to achieve a specific circulation condition, which affects the heat transfer for the heat pipes. In this study, the effect of the porosity on the effective pore radius and the capillary pressure are discussed. The rate of the test liquid rise has been used to estimate the permeability on several fiber wick samples where the porosity varies. The optimum porosity of the fiber wick structure in miniature heat pipes is found at 0.45 while the permeability approaches the maximum value of 1.26 × 10−12 m2 which results in an excellent circulation of the working fluid from the condenser to the evaporator section. Moreover, the capillary performance (K/reff) of the fiber wick is further investigated for the thermal evaluation of heat pipes. The values of the maximum heat transfer rate due to capillary limit from our prediction reach to 1.81 and 2.68 W for heat pipe diameters of 2 and 3 mm, which contain sintered fiber wick structures under optimum design conditions.

Vapor chamber with two-layer liquid supply evaporator wick for high-heat-flux devices

Modern electronic devices with high heat flux increasingly exceed the capability of thermal management method. Two-phase thermal dissipation devices such as vapor chambers offer effective method for high heat flux cooling. Various new structural designs of vapor chambers are used as effective thermal control methods for high heat flux devices. However, the optimization criteria for the capillary wick structures are different. The combinations between the structural surface parameters and pore size of the capillary wick are different, while their influence on the heat transfer performance need to be studied. In this work, it is reported that the fabrication and thermal performance of vapor chambers with multi-layer sintered wicks and multi-artery wick design for liquid supply. We numerically and experimentally characterize the two types of sintered multi-artery wick for replenishing liquid and escaping vapor effectively with high heat flux. Three kinds of combinations of different copper particle sizes were applied to the sintered wicks in order to balance the liquid collecting rate and flow resistance. The copper particles of large particle size (60 μm/100 μm/150 μm) in the upper layer wick and copper particles of small particle size (30 μm/50 μm/100 μm) the lower layer wick were applied in the vapor chambers. In the present study, as an evaluation criteria for capillary wick designs, the relationship between surface porosity, surface area and critical heat flux was analyzed to obtain the experimental optimization of structural design and pore size combination as 50/100 μm. It was found that with similar multi-artery structure wicks, higher surface area porosity can effectively increase the critical heat flux of the vapor chambers. Judging from the experiment results, the minimum through-plane direction heat transfer resistance of the vapor chamber is 0.1426 K/W, the minimum in-plane direction heat transfer resistance is 0.016 K/W, while the critical heat flux of the vapor chamber is 262 W/cm2.

A REVIEW ON PULSATING HEAT PIPES: LATEST RESEARCH, APPLICATIONS AND FUTURE SCOPE

Heat pipes have become popular as passive heat dissipation devices for many applications ranging from electronics to heat recovery in recent years. Pulsating Heat Pipe abbreviated as PHP is an exclusive category of a heat pipe which does have wick structure. It transfers heat between its evaporator and condenser sections due to the to and fro movement of working fluid caused due to the continuous change of phase taking place in it. Its operation involves combined hydrodynamic and thermodynamic effects causing the two-phase flow, making it difficult to fully understand it. Nevertheless, the PHPs have drawn the attention of investigators worldwide due to their simplicity in construction and a wide range of applications requiring high heat flux transfer. This review starts with a prologue of the attempts made by various investigators to explain the operation of PHPs through mathematical modeling. Later numerical simulations through Computational Fluid Dynamics of PHP performed by various investigators have been discussed. Review of latest experimental investigations performed on PHPs, is presented concisely in a tabular form. Novel concepts like the application of nanofluids, magnetic field and surfactant, applied for enhancing the performance of the PHPs have been discussed. At the end, applications of PHP and future scope have been discussed.

Numerical study on thermohydraulic behavior in evaporator section of wicked copper-water heat pipe at low superheat

Previous numerical studies have focused on the temperature profiles, flow pattern, heat transfer characteristics and transient behavior of wickless heat pipes. With the increase of heat dissipated power, the heat transfer capacity of the wickless heat pipe is no longer satisfied. Therefore, the research on flow and heat transfer of wicked heat pipe is more meaningful. In this paper, the numerical model of the heat pipe evaporator with a simplified rectangular wick structure was simulated. The present work to be aimed at the numerical model investigating on possible heat transfer performance. The effects of wick thickness, wick porosity, contact angle, single and double layer on heat transfer and flow characteristics were studied. For the wick thickness of 0.25, 0.5 and 1 mm, the 0.5 mm wick exhibits good versatility in heat transfer and flow. The porosity of 0.3 exhibits better heat transfer than that of 0.5, 0.7, 0.9. The value of the Nusselt number of the porosity of 0.3 reaches 142. For the contact Angle of 0, 30, 60, 90 degrees, 30 degrees has better heat transfer performance. Compared with single-layer wick, the double-layer wick can better promote thermal-hydraulic behavior.

Flow Physics of Wicking into Woven Screens with Hybrid Micro-/Nanoporous Structures.

Wicking within woven screens has attracted considerable attention due to its important role in applications concerning phase-change heat transfer and phase separation. In the present study, horizontal spreading experiments are conducted to investigate the wicking performance of woven screens by measuring the volumetric liquid intake into the screens and the liquid propagation fronts through two perpendicular high-speed cameras. Woven screens with micro (single- and multilayer)- and nano (plain, etched, and fluoridated)-porous structures are manipulated through diffusion bonding and chemical processes. The macroscopic observation indicates the substantial enhancement of the wicking capability in multilayer structures, where the interlayer microchannels could compensate for the essential deficiency of single-layer screens by providing low-resistance flow passages. Wicking capability of water is enhanced by the hydrophilic nanograsses along the wires. Furthermore, flow mechanisms within the screens are analyzed by comparisons between apparent and saturated wicking distances. In multilayer structures, the liquid spreads along the entire cross-sectional area in etched screens, while it spreads primarily along the interlayer microchannels in plain and fluoridated screens. The influence of various fluids on the wicking behavior within the woven screens is found to be fully represented by a unique parameter that captures the effects of surface tension and dynamic viscosity in the radial flow model. This work deepens the understanding of the capillary-driven flow within the woven screens with hybrid micro-/nanoporous structures and provides guidance for the design and manufacture of highly efficient wicking structures.

Optimizing L-shaped heat pipes with partially-hybrid mesh-groove wicking structures

In this study, a novel type of partially-hybrid mesh-groove wicking structures have been proposed to enhance L-shaped copper-ethanol heat pipes. Enhancements come from two aspects: (a) the enhanced evaporation via a hybrid mesh-groove wicking structure and (b) the promoted condensation by managing the unwanted flooding in the condensation section. Experimental studies have been conducted to optimize the hybrid mesh-groove wicking structures. Three types of wicking structures including grooves, partially-hybrid mesh-grooves, and fully-hybrid mesh-grooves are studied and compared. The results show that the heat pipe with partially-hybrid wicking structures substantially outperforms heat pipes with the other two types of wicking structures. The thermal resistance of the heat pipe with a partially-hybrid wicking structure has been reduced up to 57.4% compared to that of the heat pipe with axially grooves. Moreover, in this study, in order to optimize the wicking structures, the effect of mesh-layers number and charging ratio on the L-shaped partially-hybrid mesh-groove wicked heat pipe (LPHHP) has been investigated. The optimal mesh-layer numbers of the LPHHP are found to be 1-2 layers. More importantly, instead of a specific value for a given heat pipe in existing studies, this study shows that the optimal charging ratio is actually a region, which highly depends on heat loads. However, it is extremely challenging to optimize a heat pipe with such a complicated wicking structure theoretically or numerically due to the involved complex two-phase heat transfer. Thus, a regression analysis method in machine learning is proposed to optimize the charging ratio of the LPHHP.

Investigation on the effect of thermal properties by changing geometry of a heat pipe using simulation

A heat pipe is a two-phase device with a very high effective thermal conductivity and heat transfer rate. It consists of a phase change material, wick structure and an envelope. Usually, the heat pipes are circular in shape. In this paper, we analyze different shapes of the heat pipe and how it affects the performance of the pipe without changing its internal volume and central thickness. Flow property of the phase change material changes with geometry. The fluid velocity is minimum at the pipe surface and maximum at the pipe centre because of the no-slip condition. We have selected one circular and two flat geometries with a different number of edges. The advantage of flat geometry is an increased surface area of contact. ANSYS simulation softwareis used to simulate the working of the heat pipe. Several performance parameters including pressure, velocity, temperature and effective thermal conductivity were calculated and compared. The effect of an increase in the number of edges on different performance aspects of the heat pipe is studied. From the results of simulation software, it is observed that the change in geometry affects the thermal properties significantly.

Gradient wick channels for enhanced flow boiling HTC and delayed CHF

Liquid supply to wick structures of flow boiling surfaces is fundamentally restricted by the capillary limit at which the pressure drop of the wicked liquid surpasses texture-amplified capillary forces. Gradient wick structures partially decouple permeability and capillary pressure, thereby delaying the capillary limit. In this study, gradient wick channels facilitating out-of-plane liquid delivery are introduced to postpone the capillary limit and thus enhance the two-phase flow boiling heat transfer coefficient (HTC) and delay critical heat flux (CHF). Here, the permeability of the gradient wick channels is augmented by large-pore-size meshes employed near the bulk fluid while capillary pressure is maximized by small-pore-size meshes utilized near the hot boiling surface. This combination of wick structures enables to preferentially guide the cooling liquid, deionized water, from the far-field cold liquid toward the bottom hot substrate. The spatial distribution of individual gradient wick channels promotes separate liquid-vapor pathways, thus facilitating the vapor escape process. Experiments conducted here reveal that the flow boiling performance metrics of the proposed heat sink leveraging the gradient wick channels outperform those of the homogenous wick channels and solid fin channels. The proposed heat sink demonstrates a strong liquid mass flux dependency due to a combination of convective boiling and amplified wickability effects. The enhanced convective boiling could be related to surface roughness, a high number of active nucleation sites, and a large surface area available through tortuous passages of wick channels. At higher mass flow rates, effective capillary pressure available for out-of-plane wicking action also increases, thereby further boosting the wickability effect and associated heat transfer processes. This could meaningfully delay the CHF. In fact, the CHF limit was not observed on the gradient wick channel surfaces in the mass flux and wall superheat range studied. The experimental results indicated a maximum heat flux of 870 W/cm2 with a gradient wick channel heat sink, a 60% improvement compared with a plain copper surface. Furthermore, a maximum HTC of 1000 kW/m2-K at a wall superheat of 3 °C was observed, a three-fold enhancement compared with that of the plain surface. The proposed gradient wick channel topology offers new pathways for designing innovative surface technologies with high heat removal capabilities, thereby potentially improving the energy economy in myriad modern energy applications.

Analysis of Capillary Flow in a Parallel Microchannel-Based Wick Structure with Circular and Noncircular Geometries.

Capillary flow in porous media is of great significance to many different applications including microfluidics, chromatography, and passive thermal management. For example, heat pipe has been widely used in the thermal management of electronic system due to its high flexibility and low thermal resistance. However, the critical heat flux of heat pipe is often limited by the maximum capillary-driven liquid transport rate through the wicking material. A significant number of novel porous material with complex structures have been proposed in past studies to provide enhanced capillary-driven flow without substantial reduction in pore size and porosity. However, the increasing level of structural complexity often leads to a more tortuous flow path, which deprives the merits of enhanced capillarity. In this study, we examined the capillary performance of a porous material with simple geometric structures both analytically and numerically. Specifically, the capillary rate of rise of water in parallel hollow microchannels with different cross-sectional shapes is derived by solving the momentum transport equation. The relationships between the capillary flow rate and wicking height are further validated by two-phase flow simulation based on the conservative level-set method. The results demonstrate that parallel microchannel configuration, despite its geometric simplicity, provides superior capillary performance than most existing porous media in terms of both capillary flow rate and ultimate wicking height. In addition, design of noncircular cross section reduces the viscous drag and increases the packing density of the microchannels in the bulk solid without affecting the capillary pumping pressure. These features contribute to a further enhancement in the capillary performance by up to 32%. These results provide important guidance to the rational design of porous material with enhanced fluid transport property in a variety of microfluidic systems.

Theoretical Model to Investigate the Heat Transfer Mechanism through a Heat Pipe with Graphene Oxide/Distilled Water as Working Fluid

This study investigates heat transfer through a heat pipe by analysing the evaporation and condensation of working fluid (distilled water) in two parts of the heat pipe to find the phase change phenomenon. A computational methodology was developed to simulate the phase change processes and a thermal model was simulated to determine the spatial and temporal temperature profile of the heat pipe and phase change location. The velocity and location of the phase change in the evaporator and condenser sections of the pipe were calculated at each stage, as was the temperature across the domain. The thermal efficiency of the heat pipe was improved by adding graphene oxide nanoparticles at an increase of 15%. When nanoparticles were added to the distilled water, the time of the phase change phenomenon was reduced in the evaporator and condenser sections. The capillary property was enhanced when nanoparticles were deposited in the wall of the evaporator’s wick structure. The temperature distribution of the phase change phenomenon was evaluated via the evaporation and condensation processes and the location of the interface line in the two main parts of the heat pipe.

Investigation of Heat Transfer Enhancement Effect on Normal and Nano Coated Wick Structure Heat Pipes-A Comparative Assessment

Removal of heat generation is an important characteristic needs to be considered in electromechanical and electronic devices which improve the stability and feasibility of system. Despite numerous cooling methods, heat pipes are recent updating in research line. Heat pipes are one of the super conducting medium of heat energy and it is being used as an equipment to absorb more heat through phase change process of cooling medium circulated in it. It ensures the direct enhancement in heat transfer capacity and characteristics. Nowadays, improvement of the thermal performance in heat pipes getting up with various technologies, especially combination of heat pipe and Nano fluids. It has been experimentally practiced and various results are observed by previous researches that wick structure also a part of reason in improvement. The aim of this research work is to analyze the influence of wick material to improve heat transfer characteristics in heat pipes. In addition, combination of nano coated wick material with heat pipes is comparatively analyzed. From the final observed results it was found that, the best combination of wick material is supporting the better cooling requirements in electronic devices.

Thermal performance enhancement of an ultra-thin flattened heat pipe with multiple wick structure

Low heat-transport capability has been the biggest problem that has retarded the development of ultra-thin heat pipes (UFHPs). In this study, a high-performance multiple mesh wick structure, fabricated by oxidation treatment and sintering, was proposed for enhancing the thermal performance of UFHPs. The effects of various heat inputs and flattened thicknesses on the thermal performance of the UFHPs with copper mesh wicks were investigated and analysed, and the experimental results compared with those of UFHPs with conventional sintered powder wicks. The experimental results demonstrated that the heat-transport capability of the UFHP with the mesh wick could be effectively enhanced by oxidation, and the oxidized mesh wicks had the same capillary performance as sintered powder wicks. The temperature difference of the UFHP with the oxidized mesh wick was significantly lower than that of the UFHP with the un-oxidized mesh wick and sintered powder wick under identical heat input. Moreover, the performance improvement of the UFHP with the mesh wick was more significant after treatment with chemical oxidation when the flattened thickness was larger, the ultimate heat-transport capabilities of the UFHPs with a flattened thickness of 1.2 mm increased by 6 W and 9 W, respectively, compared with those with a flattened thickness of 1.0 mm.

Effect of inclination angle on the thermal performance of an ultrathin heat pipe with multi-scale wick structure

In this study, a multi-scale copper mesh wick structure fabricated by oxidation treatment and sintering is proposed for increasing the heat transport capabilities of ultrathin heat pipes (UTHPs). Experimental apparatus and a thermal resistance network model were established to analyse the heat transfer characteristics of UTHPs. The effects of various heating loads and negative inclination angles on the thermal performance of a UTHP with an oxidised mesh wick (OMHP) were experimentally investigated. The results were compared with those of an untreated mesh wick ultrathin heat pipe (NMHP) and a sintered powder wick ultrathin heat pipe (CPHP). The experimental results demonstrate that the heat transport capabilities of UTHPs with a mesh wick in the horizontal and inclined orientations were enhanced significantly owing to oxidation. The oxidised mesh wick exhibited the same or better capillary performance as the sintered powder wick in inclined orientations. Moreover, when the inclination angle increased to 90°, the temperature difference of OMHP was 36.4% and 26% lower than that of OMHP and CPHP, respectively, under the input power of 14 W. The thermal resistances of OMHP were lower than those of NMHP (by approximately 57%) and CPHP under identical test conditions.

Thermal Performances Investigation of Anti-Gravity Heat Pipe with Tapering Phase-Change Chamber

The objective of this study was to fabricate anti-gravity heat pipes with a tapering column phase-change chamber and changeable cross-sectional wick structure. The thermal performances of the anti-gravity heat pipes were experimentally investigated. Results show that the thermal resistances of the different heat pipes are less than 0.03 °C/W, except for the sharp conical chamber heat pipe under anti-gravity heating conditions (0.121 °C/W). Start-up times of different types of heat pipes are similar and the temperatures are steady within 3 to 5 min. The heat transfer ability of a conical chamber is always better than that of a cylindrical one. The performance of the sharp conical chamber heat pipe is the best under gravity assistance heating conditions. Contrarily, the blunt conical chamber heat pipe has the best heat transfer ability under anti-gravity heating conditions. Moreover, the heat transfer capability of the blunt conical chamber heat pipe is unaffected by the relative position of the heat and cold sources, which is suitable for constant temperature cooling applications with frequent switching of the heat and cold sources.

Experimental Investigation on the Vapor Chambers with Sintered Copper Powder Wick

High power electronics units generate high-density heat flux, which poses a significant threat to the reliability of these devices. The vapor chamber (VC) has a very high heat transfer rate and has a wide range of applications in the heat dissipation of electronic products. VCs with sintered copper powder wicks sized as irregular shape copper powder 50 µm (I-50 µm), I-75 µm, I-110 um, I-150 µm were studied in this paper. The effect of liquid filling ratio was discussed. The results indicated that the thermal resistance of all VCs decreased with the increase of heating power. The capillary performance of wick was the dominant factor for the heat transfer performance of VCs with different kinds of wick. A capillary performance factor was proposed to evaluate the capillary performance of VCs. The capillary performance factor of VC with the wick of I-75 µm was much higher than that of the other types of VC in this study. The heat source surface temperature of VCs could be affected by filling ratio and wick structure. But, it should be insensitive to the filling ratio when a better capillary performance factor was obtained. With the same heating area and similar structure, the maximum heat flux density of the VC would decrease as the height of vapor cavity decreased.

A water droplet-cleaning of a dusty hydrophobic surface: influence of dust layer thickness on droplet dynamics

Water droplet cleaning of a dusty hydrophobic surface is examined. Environmental dust are used in the experiments and cloaking velocity of a dust layer by a droplet fluid is measured and hemi-wicking conditions for the dust layer are analyzed adopting the pores media wick structure approach. A droplet motion on dusty and inclined hydrophobic surface is analyzed using a high speed digital imaging system. Influences of dust layer thickness, droplet volume, and surface inclination angle on the mechanisms of dust removal by a rolling droplet are evaluated. The findings revealed that dust cloaking velocity decreases exponentially with time. The droplet fluid can cloak the dust layer during its transition on the dusty surface. The transition period of droplet wetted length on the dusty surface remains longer than the cloaking time of the dust layer by the droplet fluid. Translational velocity of rolling droplet is affected by the dust layer thickness, which becomes apparent for small volume droplets. Small volume droplet (20 µL) terminates on the thick dust layer (150 µm) at low surface inclination angle (1°). The quantity of dust picked up by the rolling droplet increases as the surface inclination angle increases. The amount of dust residues remaining on the rolling droplet path is relatively larger for the thick dust layer (150 µm) as compared to its counterpart of thin dust layer (50 µm).