Interfacial Thermal Resistance Research Articles

Enhancing the Thermal Conductivity of Epoxy Composites via Constructing Oriented ZnO Nanowire-Decorated Carbon Fibers Networks.

With the miniaturization and high integration of electronic devices, high-performance thermally conductive composites have received increasing attention. The construction of hierarchical structures is an effective strategy to reduce interfacial thermal resistance and enhance composite thermal conductivity. In this study, by decorating carbon fibers (CF) with needle-like ZnO nanowires, hierarchical hybrid fillers (CF@ZnO) were rationally designed and synthesized using the hydrothermal method, which was further used to construct oriented aligned filler networks via the simple freeze-casting process. Subsequently, epoxy (EP)-based composites were prepared using the vacuum impregnation method. Compared with the pure CF, the CF@ZnO hybrid fillers led to a significant increase in thermal conductivity, which was mainly due to the fact that the ZnO nanowires could act as bridging links between CF to increase more thermally conductive pathways, which in turn reduced interfacial thermal resistance. In addition, the introduction of CF@ZnO fillers was also beneficial in improving the thermal stability of the EP-based composites, which was favorable for practical thermal management applications.

Understanding macroscopic thermal conduction in composites reinforced with 2D nanosheets

Two-dimensional (2D) nanosheets, such as graphene and hexagonal boron nitride, are considered as the most promising fillers for enhancing thermal conductivity of polymers and phase-change materials. Nevertheless, the effect of various 2D nanosheets on the effective thermal conductivity of composites is not fully understood, and the corresponding prediction model is still lacking, since numerous influence factors and complex thermal transfer networks are involved. This paper aims to study the macroscopically effective thermal conductivity of the nanosheets-reinforced composites in a systematical way, and develop a robust machine learning based prediction model. To this end, a series of representative volume elements are reconstructed based on the SEM observations of experimental samples, and high-throughput simulations are performed via the updated lattice Boltzmann scheme proposed in our recent work. The effects of shape, size, orientation, intrinsic thermal conductivity, interface thermal resistance, surface coating, and hybrid filling of the 2D nanosheets are clarified. This work could provide a deep insight into the effective thermal conductivity of the nanosheets-reinforced composites, and may offer important guidelines for the custom-design of polymer and phase-change composites with targeted thermal performances.

Enhancing thermal conductivity and dielectric properties of Al2O3@Si/polyphenylene oxide composites by surface functionalization

Recently, soaring developments in 5 G technology have raised an intensive challenge in developing polymer composites with excellent thermal conductivity and dielectric properties. Herein, Al2O3 @Si/MPPO composites were developed through synergistic modification and solution mixing methods. The double bond reaction between Al2O3 @Si and MPPO enhanced the interfacial force and greatly reduced the interfacial thermal resistance and interfacial polarization, leading to highly thermally conductive composites with excellent dielectric properties. The resultant polymer composites exhibited high thermal stability, excellent dynamic mechanical properties, a low dielectric loss of 0.00292, and a high thermal conductivity (TC) of 1.49 W/(m·K), which was 5.21 times higher than that of the pure MPPO resin, making it an ideal thermal management material for electronic devices.

Improvement of interfacial thermal resistance between TIMs and copper for better thermal management

Due to the increasing power consumption of modern electronic devices and rapid rise in heat generation, how to efficiently manage the heat dissipation becomes a challenge. The previous studies have shown the importance of interface treatment for better thermal management while the mechanism is lacking yet. Here, we study the interface thermal transport between the thermal interface materials (TIMs) and the copper substrate using both experimental measurements and theoretical calculations. The results show that after interface treatment, the thermal contact resistance between the graphite materials and copper decreases from 87.96 K · mm2 · W−1 to 20.26 K · mm2 · W−1. For the practical testing, a difference up to 7 ○C is demonstrated between the treated and untreated samples, indicating the potential of reduction of thermal contact resistance for the heat dissipation in electronic devices, which is verified in our theoretical calculation as well. Our study provides an applicable approach to enhancing the thermal stability in electronic devices by investigating the impact of the interfacial thermal resistance on heat dissipation.

Impact of nanoparticle agglomeration on thermal conductivity of molten salt based nanofluids: Insights from molecular dynamics and lattice Boltzmann methods

The nanoparticle aggregation has significant influence on heat transfer properties. The contradictions between different researches exist and the underlying mechanisms of heat conduction remain unclear. To address these issues, the thermal conductivity of solar salt-SiO2 nanofluids in the non-aggregated and aggregated states was investigated, based on the combination of the advantages of molecular dynamics (MD) in revealing physical insights and lattice Boltzmann method (LBM) in simulating properties for complex structures. LBM models were simplified on the basic of MD results. Different heat transfer physics in nanofluids at nanoscale and mesoscale were compared. The results show that the thermal conductivity of aggregated nanofluid is higher than the non-aggregated nanofluid. By analyzing the diffusion coefficient, number density and vibrational density of states, we found that the previous hypotheses (such as Brownian motion, interfacial layer and interfacial thermal resistance) cannot explain the enhanced thermal conductivity induced by the nanoparticle agglomeration. The heat transfer mechanisms of aggregated nanofluid were further analyzed from new perspectives, i.e., the contributions of different material components and fluctuation modes to heat flux. It is found that the nanoparticle aggregation leads to the nanoparticle contribution increase, indicating the formation of low thermal resistance channels within the aggregates. The heat conduction contributed by collision decreases in the aggregated state, while that contributed by potential energy increases. Moreover, the thermal conductivity of aggregated nanofluid is negatively correlated with temperature, aggregate size and fractal dimension of agglomerates, and positively correlated with mass fraction of nanoparticles, degree of agglomeration, and backbone length of each aggregate.

Construct Amorphous Polymer Interface to Enhance the Thermoelectric Performance of Commercial Bi0.5Sb1.5Te3 Materials.

Interfaces, such as grain boundaries and phase boundaries in thermoelectric (TE) materials, play a crucial role in the carrier/phonon transport. Accurate control of the features of interfaces, including composition, crystalline nature, and thickness may give rise to a promising pathway to break the trade-off between phonon and carrier transport properties, which is essential to design high-performance TE materials. In this work, the amorphous polymer interface (API) layer is introduced to the p-type commercial Bi0.5Sb1.5Te3 (BST) TE material by the liquid-phase sintering process. Due to the larger mismatch in the acoustic impedance or phonon spectra between the amorphous polymer layer and the BST phase, the additional interfacial thermal resistance is introduced, which results in a large decrease in lattice thermal conductivity. It is found that the interfacial thermal resistance at the API is much higher than that of normal grain boundary and hetero interface reported in the literature. Conversely, taking advantage of the strong electron and phonon scattering, a large net get of ZT was achieved. A maximum ZT of ∼1.22 at 350 K was obtained in the BST/polyimide-0.5% sample, which is considerably greater than that of the commercial BST matrix (∼0.99 at 350 K). Furthermore, the optimized BST/polymer sample also exhibited almost 20% enhancement in hardness compared with the pure BST sample. This work has opened a new window for designing high-performance TE composites, which may extend to other material systems.

Biomass- and Carbon Dioxide-Derived Polyurethane Networks for Thermal Interface Material Applications.

Recent environmental concerns have increased demand for renewable polymers and sustainable green resource usage, such as biomass-derived components and carbon dioxide (CO2). Herein, we present crosslinked polyurethanes (CPUs) fabricated from CO2- and biomass-derived monomers via a facile solvent-free ball milling process. Furan-containing bis(cyclic carbonate)s were synthesized through CO2 fixation and further transformed to tetraols, denoted FCTs, by aminolysis and utilized in CPU synthesis. Highly dispersed polyurethane-based hybrid composites (CPU-Ag) were also manufactured using a similar ball milling process. Due to the malleability of the CPU matrix, enabled by transcarbamoylation (dynamic covalent chemistry), CPU-based composites are expected to present very low interfacial thermal resistance between the heat sink and heat source. The characteristics of the dynamic covalent bond (i.e., urethane exchange reaction) were confirmed by the results of dynamic mechanical thermal analysis and stress relaxation analysis. Importantly, the high thermal conductivity of the CPU-based hybrid material was confirmed using laser flash analysis (up to 51.1 W/m·K). Our mechanochemical approach enables the facile preparation of sustainable polymers and hybrid composites for functional application.

Probing the thermal resistance of solid-liquid interfaces in nanofluids with molecular dynamics.

The significance of interfacial thermal resistance in the thermal conductivity of nanofluids is not well understood, in part because of the absence of measurements of this quantity. Here, we study the interfacial thermal resistance for metal-oil nanofluids of interest as heat transfer fluids for concentrating solar power, using density functional theory and molecular dynamics simulations. Insights on the role of chemical interactions in determining the interfacial thermal resistance are revealed. The results presented here showcase a general picture in which the stronger the chemical interactions between species at the interface, the lower the associated interfacial thermal resistance. The implications toward nanofluid design are discussed. We show that, for this important family of metal-oil nanofluids, the interfacial thermal resistance values are low enough so that it is possible to afford a reduction in particle size, minimizing stability and rheological issues while still offering enhancement in the effective thermal conductivity with respect to the base fluid.

Preparation of diatomite-based porous ceramics containing interlayer porous MgO by low-temperature sintering for integration of high strength and low thermal conductivity

In this work, hierarchical porous ceramics based on diatomite with both high strength and low thermal conductivity were prepared by low-temperature sintering using modified diatomite and dolomite as the main raw materials. In particular, dolomite served both as a pore-forming agent to produce CO2 gas and as a ceramic component to produce porous MgO in situ. The prepared porous ceramics exhibited a hierarchical pore structure, retaining 2–300 nm nano-pores of the diatomite itself while using dolomite decomposition to produce 1–10 µm macro-pores and porous MgO with inter-layer pore sizes of 50–300 nm. The main phases of porous ceramics were cristobalite phase, pyroxene phase, wollastonite phase and MgO phase with special structure. The effect of dolomite addition on the mechanical properties and thermal insulation of porous ceramics was investigated. It was found that the addition of 30% dolomite resulted in a porous ceramic with a porosity of 59.8% and the most favorable pore size distribution. At this time, the presence of wollastonite and pyroxene-like products in the porous ceramics contributed to the highest compressive and bending strengths of 29.66 MPa and 7.22 MPa, respectively. The lowest thermal conductivity of the porous ceramics reached 0.094 W·m−1K−1, which can be attributed to the synergistic effect of the hierarchical pores and the increasing interfacial thermal resistance. Overall, the prepared hierarchical porous ceramics exhibited great potential as an alternative material to ceramic fiber insulation in high-temperature kilns.

Phonon thermal transport in bilayer polycrystalline graphene nanoribbons: effects of interlayer interaction, grain size, and vacancy defects

In this paper, molecular dynamics simulations have been employed to investigate the phonon thermal transport in bilayer polycrystalline graphene nanoribbon (pGNR/pGNR), compared with bilayer graphene nanoribbon (GNR/GNR) and pGNR/GNR heterostructure. The interfacial thermal resistance (ITR) of bilayer structures was also calculated using the heat dissipation method. The effects of interlayer interaction, grain size, and vacancy defects on ITR and in-plane phonon thermal conductivity of bilayer structures were investigated. It was found that the ITR as well as in-plane phonon thermal conductivity of pGNR/pGNR was less than that of pGNR/GNR and much less than that of GNR/GNR, for the same size. For the studied bilayer structures, both the ITR and in-plane phonon thermal conductivity decrease with increasing interlayer interactions. Moreover, ITR increases with increasing grain area size whereas decreases with increasing vacancy defects in pGNR-based bilayers. The introduction of pGNR interface roughness and vacancy defects results in an enhanced phonon coupling in pGNR-based bilayers compared to pure GNR/GNR bilayers. Presented simulation investigations will help to understand the interlayer thermal transport properties of polycrystalline graphene and provide essential guidance for experimentally regulating phonon thermal transport between layers of polycrystalline graphene.

Interface Contact Thermal Resistance of Die Attach in High-Power Laser Diode Packages

The reliability of packaged laser diodes is heavily dependent on the quality of the die attach. Even a small void or delamination may result in a sudden increase in junction temperature, eventually leading to failure of the operation. The contact thermal resistance at the interface between the die attach and the heat sink plays a critical role in thermal management of high-power laser diode packages. This paper focuses on the investigation of interface contact thermal resistance of the die attach using thermal transient analysis. The structure function of the heat flow path in the T3ster thermal resistance testing experiment is utilized. By analyzing the structure function of the transient thermal characteristics, it was determined that interface thermal resistance between the chip and solder was 0.38 K/W, while the resistance between solder and heat sink was 0.36 K/W. The simulation and measurement results showed excellent agreement, indicating that it is possible to accurately predict the interface contact area of the die attach in the F-mount packaged single emitter laser diode. Additionally, the proportion of interface contact thermal resistance in the total package thermal resistance can be used to evaluate the quality of the die attach.

Molecular dynamics investigation on the interfacial thermal resistance between annealed pyrolytic graphite and copper.

Modern highly integrated microelectronic products often face the challenge of internal heat dissipation, leading to a significant decrease in their operational efficiency. Annealed Pyrolytic Graphite (APG), due to its superior thermal conductivity, has garnered attention from researchers. The interface thermal resistance between APG and supporting materials like copper significantly affects heat transfer during APG's operation. Existing studies rarely delve into the influence of factors such as the shape of APG material interfaces on thermal resistance from a microscopic perspective. In this paper, utilizing transient thermo-reflectance method and non-equilibrium molecular dynamics simulations, the interface thermal resistance of the APG-Cu structure was investigated under different conditions. The impact of parameters such as copper thickness, interface micro-surface morphology, and APG thickness on the calculated interface thermal resistance was examined. Simulation results revealed that copper thickness had a minor effect on the interface thermal resistance. This is because the phonon participation ratio remains unaffected by changes in the thickness of the copper layer. The interfacial thermal resistance beneath microscopically cylindrical copper surfaces was considerably lower than that of rectangular copper surfaces. This is because beneath the cylindrical surface, the enlarged interface contact area facilitates enhanced thermal transport between the interfaces. The computed results of the radial distribution function in the paper also indirectly validate this viewpoint. The magnitude of interfacial thermal resistance for different APG layers was influenced by the coupling effect of intermolecular forces and the layered stacking structure of APG. The interfacial thermal resistance under the condition of three layers of APG reaches its minimum value, which is 2.2 × 10-9 (K m2 W-1). Furthermore, from the phonon perspective, it is found that the interfacial thermal resistance with different numbers of APG layers is closely related to the localization or delocalization state of phonons. As the number of APG layers increased, the interface thermal resistance showed a trend of initial decrease followed by an increase, this is because the average phonon participation ratio increases and then decreases with the number of APG layers. The average phonon participation ratio reaches its maximum value of 0.45778 under the condition of three layers of APG.

Heat and mass transfer of water flow in graphene nanochannels: effect of pressure and interfacial interaction.

The low-resistance transport of water within graphene nanochannels makes it promising for electronic cooling applications. However, how the water pressure and the water-graphene interaction strength affect the flow field and the thermal transfer, including velocity slip, friction coefficient, Nusselt number, temperature slip, interfacial thermal resistance, and variation of physical properties, is still not clearly understood. In this paper, we employ molecular dynamics (MD) simulations to investigate qualitatively the heat transfer of water flow in graphene nanochannels. Our results reveal that the water peak density near the wall increases approximately linearly with water pressure and water-graphene interaction strength. The water peak density near the water-graphene interface is a key factor in regulating interfacial flow and heat transfer characteristics. Under constant inlet temperature, the relationship between velocity slip length and peak density follows a consistent power function, simply modifying the pressure or the interaction strength doesn't bring a specific effect. The Nusselt number and interfacial thermal resistance are not solely dependent on water peak density; at the same water peak density, increasing interaction strength results in lower interfacial thermal resistance compared to increasing pressure. Increasing pressure improves both interfacial heat transfer and internal heat transfer of water. Furthermore, the convection heat transfer coefficient increases approximately linearly with flow resistance when pressure and interaction strength vary moderately. Finally, we notice that pressure and interaction strength hardly affect the variation range of viscosity and thermal conductivity at a channel height of 10-12 nm. These qualitative insights could lead to the development of more efficient cooling systems for electronic devices.

Enhancement of the photoacoustic effect during the light-particle interaction.

Exogenous photoacoustic contrast agents such as gold nanoparticles are widely utilized in photoacoustic imaging. Enhancing the photoacoustic performance of gold nanoparticles is pivotal for improving the quality and expanding the application scope of photoacoustic imaging. In this work, the photothermal and photoacoustic responses of gold nanospheres surrounded by water excited with a pulsed laser are obtained via a two-temperature model. The interplay between pulse duration and interface thermal resistance and its effect on the photothermal and photoacoustic performances are uncovered quantitatively. The results reveal that, as the pulse duration decreases, increasing the interfacial thermal conductivity can substantially enhance heat transfer between the gold nanosphere and the surrounding water. However, this approach does not effectively enhance the photoacoustic performance. Interestingly, when increasing the thermal conductivity, it was found that there is an optimal pulse duration within the range of 10 ps-10 ns. Employing an incident pulse laser with this optimal pulse duration can maximize the enhancement of the photoacoustic signal.

Analysis of GAAFET’s transient heat transport process based on phonon hydrodynamic equations

Compared to the classical Fourier’s law, the phonon hydrodynamic model has demonstrated significant advantages in describing ultrafast phonon heat transport at the nanoscale. The gate-all-around field-effect transistor (GAAFET) greatly optimizes its electrical performance through its three-dimensional channel design, but its nanoscale characteristics also lead to challenges such as self-heating and localized overheating. Therefore, it is of great significance to study the internal heat transport mechanism of GAAFET devices to obtain the thermal process and heat distribution characteristics. Based on this, this paper conducts theoretical and numerical simulation analyses on the phonon heat transfer characteristics within nanoscale GAAFET devices. Firstly, based on the phonon Boltzmann equation, the phonon hydrodynamic model and boundary conditions are rigorously derived, establishing a numerical solution method based on finite elements. For the novel GAAFET devices, the effects of factors such as surface roughness, channel length, channel radius, gate dielectric, and interface thermal resistance on their heat transfer characteristics are analyzed. The research results indicate that the larger the surface roughness, the smaller the channel length and the channel radius, the larger the interface thermal resistance leads to the higher hot spot peak temperature. The non-Fourier heat analysis method based on the phonon hydrodynamic model and temperature jump condition within the continuous medium framework constructed in this paper can accurately predict the non-Fourier phonon heat conduction process inside GAAFET and reveal the mechanisms of resistive scattering and phonon/interface scattering. This work provides important theoretical support for further optimizing the thermal reliability design of GAAFET, improving its thermal stability, and operational performance.

Patterned liquid metal embedded in brush-shaped polymers for dynamic thermal management.

Interface thermal resistance has become a crucial barrier to effective thermal management in high-performance electronics and sensors. The growing complexity of operational conditions, such as irregular and dynamic surfaces, demands thermal interface materials (TIMs) to possess high thermal conductivity and soft elasticity. However, developing materials that simultaneously combine soft elasticity and high thermal conductivity remains a challenging task. Herein, we utilize a vertically oriented graphene aerogel (VGA) and rationally design liquid metal (LM) networks to achieve directional and adjustable pathways within the composite. Subsequently, we leverage the advantages of the low elastic modulus and high deformation capabilities of brush-shaped polydimethylsiloxane (BPDMS), together with the bicontinuous thermal conduction path constructed by VGA and LM networks. Ultimately, the designed composite of patterned liquid metal/vertically oriented graphene aerogel/brush-shaped PDMS (LM-VGA/BPDMS) shows a high thermal conductivity (7.11 W m-1 K-1), an ultra-low elastic modulus (10.13 kPa), excellent resilience, and a low interface thermal resistance (14.1 K mm2 W-1). This LM-VGA/BPDMS soft composite showcases a stable heat dissipation capability at dynamically changing interfaces, as well as excellent adaptability to different irregular surfaces. This strategy holds important application prospects in the fields of interface thermal management and thermal sensing in extremely complex environments.

Molecular dynamics study on effect of wettability on boiling heat transfer of thin liquid films

How surface wettability affects boiling heat transfer of thin liquid film on a nanoscale remains a challenging research topic. In this work, the effects of wettability on the nanoscale boiling heat transfer for a thin liquid film on hydrophilic surface and hydrophobic surface are investigated by molecular dynamics simulation. Results demonstrate that the hydrophilic surface has better heat transfer performance than the hydrophobic surface. It has a shorter boiling onset time, higher temperature, heat flux, interfacial thermal conductance, and weakened interfacial thermal resistance. The hydrophilic surface throughout has higher critical heat flux than the hydrophobic surface in both macro-system and nanoscale system. Besides, a two-dimensional surface potential energy is proposed to reveal the mechanism of wettability affecting the boiling heat transfer. The absolute value of potential energy in one regular unit of hydrophilicity (–0.34 eV) is much higher than that of hydrophobicity (–0.09 eV). That is the crucial reason why the heat transfer enhancement via improving surface wettability should be primarily the powerful surface potential energy. In addition, the interaction energy is calculated to further address the nucleation mechanism and heat transfer performance for liquid film on different wettability surfaces. The interaction energy values are ordered as <i>I</i><sub>phi</sub> (1.57 eV/nm<sup>2</sup>) > <i>I</i><sub>water</sub> (0.48 eV/nm<sup>2</sup>) > <i>I</i><sub>pho</sub> (0.26 eV/nm<sup>2</sup>), indicating that the better heat transfer performance of hydrophilic surface is because of the large interaction energy at the solid/liquid interface. Besides, the bubble nucleation on a hydrophilic surface needs absorbing more energy and occurs inside the thin liquid film, while it needs absorbing less energy and triggering off at the solid/liquid interface with hydrophobicity. Those uncover the principal mechanisms of how wettability influences the bubble nucleation and boiling heat transfer performance on a nanoscale.

Collaborative enhancement of thermal diffusivities and mechanical properties of Csf-Cu/Mg composites via introducing Cu coating with different thicknesses

Mg alloy matrix composites reinforced with short carbon fibers (Csf/Mg) are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight, excellent mechanical properties, and heat dissipation. However, the different characteristics of Csf and Mg alloy make the interface a critical issue affecting the synergistic improvement of thermal and mechanical properties of the composites. Here, Cu coating with different thicknesses is introduced to modify the Csf/Mg interface, so as to simultaneously enhance the thermal and mechanical performances, which can combine the advantages of coating modification and matrix alloying. Results reveal that thermal diffusivity (TD) of 3-Csf-Cu/Mg composites is as high as 22.12 mm2/s and an enhancement of 52.97% is achieved compared with Csf/Mg composites, as well as 16.3% enhancement of ultimate compressive strength (UCS) in the longitudinal direction, 8.84% improvement of UCS in the transverse direction, and 53.08% increasement of ultimate tensile strength (UTS). Such improvement can be ascribed to the formation of intermetallic compounds. The formation of intermetallic compounds can not only effectively alleviate the lattice distortion of the matrix and decrease interfacial thermal resistance, but also bear the loads. Our work is of great significance for designing Csf/Mg composites with integrated structure and function.

Covalent-assisted construction of “scale-like” boron nitride/polyimide thermal interface materials with high thermal conductivity

Polyimide (PI) is a special engineering plastic with high strength, high modulus, high temperature resistance and corrosion resistance, but its poor thermal conductivity limits its application in high-power miniaturized electric and electronic equipment. In this study, surface-activated and modified boron nitride (m-BN) is polymerized in situ and coated to form a “scale-like” composite thermal interface material (m-BN/PI) with PI. Moreover, the m-BN@PI composite films obtained by a simple co-blending process of m-BN and PI are used as a comparison. The in-plane thermal conductivity of m-BN/PI composite reached 4.43 W m−1 K−1, when the filler content is 30 wt %, which is about 12 times higher than that of the pure PI film (0.37 W m−1 K−1). At this load, the in-plane thermal conductivity of m-BN@PI is only 3.94 W m−1 K−1. In addition, the covalent bonding between m-BN and PI molecular chains in m-BN/PI effectively reduces the interfacial thermal resistance by fitting the EMT and Foygel models. Finally, using the m-BN/PI composite film as a thermal interface material placed at the CPU location, its role in the heat dissipation process of electronic devices is demonstrated.

Molecular dynamics investigation of the effects of thin periodic defective graphene on the interfacial thermal resistance at liquid–solid interfaces

By coating a heat transfer surface with a thin film, we can improve the heat and mass transfer as in the case of micro heat pipes. This study investigates the effects of periodic defective graphene on the density depletion length and the interfacial thermal resistance at the liquid–solid interface through a nonequilibrium molecular dynamics simulation of a water–graphene–Cu system. The results show that the defect concentration of thin graphene plays an essential role in the interfacial thermal resistance. Specifically, it determines the relationship between the density depletion length and the interfacial thermal resistance between water and solid surfaces. In contrast to a pristine graphene coating, a periodic defective graphene coating affects the density depletion length, while the interfacial thermal resistance at the copper–liquid interface decreases clearly with the defect concentration at the strong interaction strength between thin graphene and water.