Modelling of heat transfer processes in micro and nano-scale structures

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Nano and microscale devices are becoming increasingly more prevalent as sophisticated manufacturing processes provide a pathway for miniaturization. Many of these devices display the same physical behaviour of their macro or meso-scale counterparts, however heat transfer can differ significantly as scale dimensions are reduced. Three distinct areas of research will be explored to provide insight into the complex issues associated with nanoscale heat transfer.1. Heat transfer models are often presented in the form of dimensionless groups that combine logical combinations of thermal system characteristics. By maintaining the overall magnitude of the groups, it is possible to create a situation where changes in fluid properties lead to analogous changes in scale length. Experiments will be designed that allow nanoscale characteristic lengths to be modeled by working with larger scale dimensions but in an ambient environment that is at a reduced pressure thereby allowing conventional heat transfer measurement techniques to be used to measure nano-scale conditions.2. Analytical models will be developed to simulate the combined effects of electron-phonon driven heat conduction at reduced scale lengths. Semi-conductor devices and current carrying wires, such as shape memory alloys, depend on electron flow to complete the electrical circuit while heat flows are typically generated through electron-phonon interactions. Physical models will be developed that allow for the vibrational characteristics of phonon transport in combination with the directional flow of electron transport.3. An experimental program will be implemented to explore the development of thermocouple junctions using lithographic techniques and vapour deposition to form temperature sensors in the order of 50 - 100 nano meters. These temperature sensing devices will be used to create a nanoscale temperature probe that can be coupled with a scanning electron microscope to measure point-source temperatures of nanoscale devices.