Nanoscale Heat Transfer

The transport processes of mass, momentum, and heat in nanoscale systems are dominated by the large surface-to-volume ratio inherent at this length scale. To understand these processes we have to extend our macroscale models to include the effect of the micro structure eg.: surface chemistry, atomic scale corrugation, and fluid- and and solid impurities. In this rearch we study nanoscale heat transfer and we apply tempeture gradients to drive solid and fluid nanoparticles.

 

Thermophoretic Motion of Gold and Water Nanodroplets Confined inside Carbon Nanotubes

We study the thermophoretic motion of solid gold nanoparticles and water nanodroplets confined inside carbon nanotubes using molecular dynamics simulations. The nanodroplet moves in the direction opposite to the imposed thermal gradient with a terminal velocity that is linearly proportional to the gradient. We find that the motion along the axial is associated with a solid body rotation of the water nanodroplet that follows the helical symmetry of the carbon nanotube.

Schematic of the water nanodroplet confined inside a carbon nanotube. A thermal gradient is imposed by heating the end sections (in red) of the carbon nanotube.

Thermal Conductivity of Carbon Nanotubes in Aqueous Solutions

Carbon nanotube (CNT) suspensions in alpha-alkene liquids have exhibited marked increases in thermal conductivity, leading to interest in these systems for heat management applications. Pristine CNTs have large thermal conductivity in  the axial direction, but small values have been observed in the radial direction between CNTs and surrounding media. The objective of our study is  to determine the characteristics of the solution that can maximize this radial heat transfer.

Hexanamine mediates the thermal properties of solvated CNTs.

Hexanamine mediates the thermal properties of solvated CNTs. Hexanamine (CH3-(CH2)5-NH2) is added to the system to study the thermal resinstance of solvated CNTs. The results obtained from the NEMD simulations of the pristine carbon nanotube-water system reveal a significant jump in the water temperature at the interface.

Kapitza resistance between water and graphene

Several studies have indicated that graphene is a promising material for improved heat dissipation in integrated chips due to its high thermal conductivity. Of particular interest are suspensions of nanoscale graphene flakes and carbon nanotubes in liquids as they exhibit substantially larger thermal conductivity than that of pure liquids. However, there is a discrepancy of more than an order of magnitude between the theoretically predicted and the measured thermal conductivity of nanofluids. This discrepancy is attributed to uncertainties on the value of the interfacial thermal (Kapitza) resistance.

We have investigated the thermal transport across water−graphene interface through Non-Equilibrium Molecular Dynamics simulations. Among our findings is the fact that the Kapitza resistance is critically affected by the water layering at the interface and more specifically by the value of the first density peak of water adjacent to the interface. The magnitude of the first density peak of a liquid adjacent to the solid may be tuned to control the heat dissipation in micro- and nanofluidic systemsю

People: Alvaro Foletti, Jens Honoré Walther, Jie Chen, Dmitry Alexeev
People: Professor Chriostofer Hierold (ETHZ), Dr. Richard Jaffe (NASA Ames), Professor Eftimios Kaxiras (Harvard), Harvey Zambrano (Technical University of Denmark)

Publications

2016

  • J. Chen, J. H. Walther, and P. Koumoutsakos, “Ultrafast cooling by covalently bonded graphene-carbon nanotube hybrid immersed in water,” Nanotechnology, vol. 27, iss. 46, p. 465705, 2016.
    [BibTeX] [PDF] [DOI]
    @article{chen2016a,
    author = {Jie Chen and Jens H Walther and Petros Koumoutsakos},
    doi = {10.1088/0957-4484/27/46/465705},
    journal = {Nanotechnology},
    month = {oct},
    number = {46},
    pages = {465705},
    publisher = {{IOP} Publishing},
    title = {Ultrafast cooling by covalently bonded graphene-carbon nanotube hybrid immersed in water},
    url = {http://www.cse-lab.ethz.ch/wp-content/papercite-data/pdf/chen2016a.pdf},
    volume = {27},
    year = {2016}
    }

2015

  • D. Alexeev, J. Chen, J. H. Walther, K. P. Giapis, P. Angelikopoulos, and P. Koumoutsakos, “Kapitza resistance between few-layer graphene and water: liquid layering effects,” Nano letters, vol. 15, iss. 9, pp. 5744-5749, 2015.
    [BibTeX] [Abstract] [Supplemental] [PDF] [DOI]

    The Kapitza resistance (R_K) between few-layer graphene (FLG) and water was studied using molecular dynamics simulations. The R_K was found to depend on the number of the layers in the FLG though, surprisingly, not on the water block thickness. This distinct size dependence is attributed to the large difference in the phonon mean free path between the FLG and water. Remarkably, R_K is strongly dependent on the layering of water adjacent to the FLG, exhibiting an inverse proportionality relationship to the peak density of the first water layer, which is consistent with better acoustic phonon matching between FLG and water. These findings suggest novel ways to engineer the thermal transport properties of solid{—}liquid interfaces by controlling and regulating the liquid layering at the interface.

    @article{alexeev2015a,
    author = {Dmitry Alexeev and Jie Chen and Jens H. Walther and Konstantinos P. Giapis and Panagiotis Angelikopoulos and Petros Koumoutsakos},
    doi = {10.1021/acs.nanolett.5b03024},
    journal = {Nano Letters},
    month = {sep},
    number = {9},
    pages = {5744--5749},
    publisher = {American Chemical Society ({ACS})},
    supplemental = {http://www.cse-lab.ethz.ch/wp-content/papercite-data/pdf/alexeev2015a_supplemental.pdf},
    title = {Kapitza Resistance between Few-Layer Graphene and Water: Liquid Layering Effects},
    url = {http://www.cse-lab.ethz.ch/wp-content/papercite-data/pdf/alexeev2015a.pdf},
    volume = {15},
    year = {2015}
    }

  • J. Chen, J. H. Walther, and P. Koumoutsakos, “Covalently bonded graphene-carbon nanotube hybrid for high-performance thermal interfaces,” Advanced functional materials, vol. 25, iss. 48, pp. 7539-7545, 2015.
    [BibTeX] [Abstract] [PDF] [DOI]

    The remarkable thermal properties of graphene and carbon nanotubes (CNTs) have been the subject of intensive investigations for the thermal management of integrated circuits. However, the small contact area of CNTs and the large anisotropic heat conduction of graphene have hindered their applications as effective thermal interface materials (TIMs). Here, a covalently bonded graphene{—}CNT (G-CNT) hybrid is presented that multiplies the axial heat transfer capability of individual CNTs through their parallel arrangement, while at the same time it provides a large contact area for efficient heat extraction. Through computer simulations, it is demonstrated that the G-CNT outperforms few-layer graphene by more than 2 orders of magnitude for the c-axis heat transfer, while its thermal resistance is 3 orders of magnitude lower than the state-of-the-art TIMs. We show that heat can be removed from the G-CNT by immersing it in a liquid. The heat transfer characteristics of G-CNT suggest that it has the potential to revolutionize the design of high-performance TIMs.

    @article{chen2015a,
    author = {Jie Chen and Jens H. Walther and Petros Koumoutsakos},
    doi = {10.1002/adfm.201501593},
    journal = {Advanced Functional Materials},
    month = {nov},
    number = {48},
    pages = {7539--7545},
    publisher = {Wiley-Blackwell},
    title = {Covalently Bonded Graphene-Carbon Nanotube Hybrid for High-Performance Thermal Interfaces},
    url = {http://www.cse-lab.ethz.ch/wp-content/papercite-data/pdf/chen2015a.pdf},
    volume = {25},
    year = {2015}
    }

2014

  • J. Chen, J. H. Walther, and P. Koumoutsakos, “Strain engineering of kapitza resistance in few-layer graphene,” Nano letters, vol. 14, iss. 2, pp. 819-825, 2014.
    [BibTeX] [Abstract] [PDF] [DOI]

    We demonstrate through molecular dynamics simulations that the Kapitza resistance in few-layer graphene (FLG) can be controlled by applying mechanical strain. For unstrained FLG, the Kapitza resistance decreases with the increase of thickness and reaches an asymptotic value of 6 {\texttimes} 10{—}10 m{\^{}}2 K/W at a thickness about 16 nm. Uniaxial cross-plane strain is found to increase the Kapitza resistance in FLG monotonically, when the applied strain varies from compressive to tensile. Moreover, uniaxial strain couples the in-plane and out-of-plane strain/stress when the surface of FLG is buckled. We find that with a compressive cross-plane stress of 2 GPa, the Kapitza resistance is reduced by about 50%. On the other hand it is almost tripled with a tensile cross-plane stress of 1 GPa. Remarkably, compressive in-plane strain can either increase or reduce the Kapitza resistance, depending on the specific way it is applied. Our study suggests that graphene can be exploited for both heat dissipation and insulation through strain engineering.

    @article{chen2014a,
    author = {Jie Chen and Jens H. Walther and Petros Koumoutsakos},
    doi = {10.1021/nl404182k},
    journal = {Nano Letters},
    month = {feb},
    number = {2},
    pages = {819--825},
    publisher = {American Chemical Society ({ACS})},
    title = {Strain Engineering of Kapitza Resistance in Few-Layer Graphene},
    url = {http://www.cse-lab.ethz.ch/wp-content/papercite-data/pdf/chen2014a.pdf},
    volume = {14},
    year = {2014}
    }

2007

  • P. A. E. Schoen, J. H. Walther, D. Poulikakos, and P. Koumoutsakos, “Phonon assisted thermophoretic motion of gold nanoparticles inside carbon nanotubes,” Applied physics letters, vol. 90, iss. 25, p. 253116, 2007.
    [BibTeX] [Abstract] [PDF] [DOI]

    The authors investigate the thermally driven mass transport of gold nanoparticles confined inside carbon nanotubes using molecular dynamics simulations. The observed thermophoretic motion of the gold nanoparticles correlates with the phonon dispersion exhibited by a standard carbon nanotube and, in particular, with the breathing mode of the tube. Additionally, the results show an increased static friction for gold nanoparticles confines inside a zig-zag carbon nanotube when increasing the size (length) of the nanoparticles. However, an unexpected, opposite trend is observed for the same nanoparticles inside armchair tubes. (c) 2007 American Institute of Physics.

    @article{schoen2007a,
    author = {Philipp A. E. Schoen and Jens H. Walther and Dimos Poulikakos and Petros Koumoutsakos},
    doi = {10.1063/1.2748367},
    journal = {Applied Physics Letters},
    month = {jun},
    number = {25},
    pages = {253116},
    publisher = {{AIP} Publishing},
    title = {Phonon assisted thermophoretic motion of gold nanoparticles inside carbon nanotubes},
    url = {http://www.cse-lab.ethz.ch/wp-content/papercite-data/pdf/schoen2007a.pdf},
    volume = {90},
    year = {2007}
    }

2006

  • P. A. E. Schoen, J. H. Walther, S. Arcidiacono, D. Poulikakos, and P. Koumoutsakos, “Nanoparticle traffic on helical tracks: thermophoretic mass transport through carbon nanotubes,” Nano letters, vol. 6, iss. 9, pp. 1910-1917, 2006.
    [BibTeX] [Abstract] [PDF] [DOI]

    Using molecular dynamics simulations, we demonstrate and quantify thermophoretic motion of solid gold nanoparticles inside carbon nanotubes subject to wall temperature gradients ranging from 0.4 to 25 K/nm. For temperature gradients below 1 K/nm, we find that the particles move “on tracks” in a predictable fashion as they follow unique helical orbits depending on the geometry of the carbon nanotubes. These findings markedly advance our knowledge of mass transport mechanisms relevant to nanoscale applications.

    @article{schoen2006a,
    author = {Philipp A. E. Schoen and Jens H. Walther and Salvatore Arcidiacono and Dimos Poulikakos and Petros Koumoutsakos},
    doi = {10.1021/nl060982r},
    journal = {Nano Letters},
    month = {sep},
    number = {9},
    pages = {1910--1917},
    publisher = {American Chemical Society ({ACS})},
    title = {Nanoparticle Traffic on Helical Tracks: Thermophoretic Mass Transport through Carbon Nanotubes},
    url = {http://www.cse-lab.ethz.ch/wp-content/papercite-data/pdf/schoen2006a.pdf},
    volume = {6},
    year = {2006}
    }