Degree Type

Dissertation

Date of Award

2015

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

First Advisor

Xinwei Wang

Abstract

Thermal transport in DNA is systematically studied to facilitate the development of DNA-based nanoelectronics in thermal management aspect. Synthesis of crystalline DNA-composited microfiber and microfilm, DNA nanofiber and DNA nanofiber array are developed in sequence to enable the thermal transport study in them. Thermo-physical properties, including thermal conductivity, thermal diffusivity, and volumetric heat capacity, for all of the DNA samples are reported. The thermal conductivity of DNA microfiber is evaluated to be 0.33 W/m·K at room temperature. With the formation of crystalline DNA-NaCl complexes, DNA molecules are speculated to be aligned with the crystal structure of NaCl during crystallization, which results in a significant enhancement of thermal transport. The thermal conduction can also be improved by eliminating structural defects in DNA samples based on the newly-established thermal reffusivity theory. Thermal reffusivity is the inverse of thermal diffusivity and is introduced to quantitatively evaluate phonon scattering induced by structural defects. The structural size for defect-induced phonon scattering is determined to be 0.8 nm for DNA microfiber, in the same order of magnitude as the characteristic size of DNA. As the structural size for defect-induced phonon scattering approaches infinity, the thermal transport potential in defect-free material can be reached. By estimation, the thermal conductivity/diffusivity will be promoted by 36~61% without structural defects in DNA microfiber. Compared to microfiber, DNA nanofiber possesses a higher thermal conductivity due to more condensed and oriented structures, as well as less structural defects. The structural size for defect-induced phonon scattering is 1.6 nm in DNA nanofiber, twice of that in DNA microfiber. The thermal conductivity of DNA nanofiber with perfect structure is predicted to reach 2.3 W/m·K. In addition, nanoscale Ir thin film on DNA microfiber shows a similar intrinsic electrical resistivity as bulk Ir, which is proposed to be preserved by coherent quantum tunneling and diffusive thermal hopping for electron transport in DNA.

Copyright Owner

Zaoli Xu

Language

en

File Format

application/pdf

File Size

105 pages

Included in

Engineering Commons

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