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Research Papers: Micro/Nanoscale Heat Transfer

# A Molecular Dynamics Study on Heat Transfer Characteristics Over the Interface of Self-Assembled Monolayer and Water Solvent

[+] Author and Article Information
Gota Kikugawa

Institute of Fluid Science,
Tohoku University,
2-1-1 Katahira,
Aoba-ku, Sendai 980-8577, Japan
e-mail: kikugawa@microheat.ifs.tohoku.ac.jp

Taku Ohara

Institute of Fluid Science,
Tohoku University,
2-1-1 Katahira,
Aoba-ku, Sendai 980-8577, Japan

Tohru Kawaguchi

DENSO CORPORATION,
500-1 Minamiyama, Komenoki-cho,
Nisshin, Aichi 470-0111, Japan

Ikuya Kinefuchi, Yoichiro Matsumoto

Department of Mechanical Engineering,
The University of Tokyo,
7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-8656, Japan

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received July 25, 2013; final manuscript received June 18, 2014; published online July 15, 2014. Assoc. Editor: Patrick E. Phelan.

J. Heat Transfer 136(10), 102401 (Jul 15, 2014) (5 pages) Paper No: HT-13-1369; doi: 10.1115/1.4027910 History: Received July 25, 2013; Revised June 18, 2014

## Abstract

We performed molecular dynamics (MD) simulations of the interface which is comprised of self-assembled monolayer (SAM) and water solvent to investigate heat transfer characteristics. In particular, local thermal boundary conductance (TBC), which is an inverse of so-called Kapitza resistance, at the SAM–solvent interface was evaluated by using the nonequilibrium MD (NEMD) technique in which the one-dimensional thermal energy flux was imposed across the interface. By using two kinds of SAM terminal with hydrophobic and hydrophilic properties, the local TBCs of these interfaces with water solvent were evaluated, and the result showed a critical difference due to an affinity between SAM and solvent. In order to elucidate the molecular-scale mechanism that makes this difference, microscopic components contributing to thermal energy flux across the interface of hydrophilic SAM and water were evaluated in detail, i.e., the total thermal energy flux is decomposed into the heat transfer modes such as the contribution of molecular transport and that of energy exchange by molecular interactions. These heat transfer modes were also compared with those in the bulk water.

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## Figures

Fig. 1

A snapshot of the computational system of the C11OH-SAM/water system. The wireframe around the molecular system indicates a boundary of the MD basic cell and 3D periodic boundary condition is applied to that.

Fig. 2

Number density profiles and temperature distribution in (a) the C12-SAM/water system and (b) the C11OH-SAM/water system. Thick marked lines denotes the temperature, and thin solid lines denote the number density of each constituent. For alkanethiol SAM phase, green, yellow, red, and gray lines indicate the number density of carbon, sulfur, oxygen, and hydrogen atom, respectively. Only half of the cell is depicted due to system symmetry.

Fig. 3

Probability distribution of tilt angle of SAM molecules from the surface normal in both systems. Each profiles are normalized by sin θ, where θ is tilt angle.

Fig. 4

Contributions to total thermal energy flux at the SAM–solvent interface region in the C11OH-SAM/water system

Fig. 5

Contributions to total thermal energy flux in the bulk-like region of water solvent in the C11OH-SAM/water system

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