Nanostructures have thermal transport properties quite different from those of their bulk counterparts. Experimental techniques capable of measuring very small temperature changes and heat flux are necessary tools towards the goal of understanding the effects of nanostructuring on thermal transport properties. This project will develop a new method for measuring thermal transport through single nanostructures that is based on the deflection of bi-material microcantilevers to heat flow. This deflection occurs due to the difference in thermal expansion coefficients of the two layers of material. Due to their small size, bi-material cantilevers are extremely sensitive thermometers. In the new measurement technique, a single nanostructure is suspended between the ends of two cantilevers. One cantilever acts as a heater and the other as a sensor for heat flowing through the suspended nanostructure. The method will combine the extraordinary sensitivity of cantilever-based thermal measurements with the idea of the suspended microdevice method invented by Philip Kim and Li Shi. The investigator has developed a reliable method for suspending electrospun polymer nanowires between two cantilevers, making them a suitable choice for studying the role of nanostructuring in polymeric materials as well as demonstrating the ability of the method to measure thermal conduction through single nanostructures. Especially for low thermal conductivity materials such as polymers and polymer nanocomposites, the high sensitivity of bi-material cantilevers makes them an ideal platform for measuring thermal conductance. The technique developed in this work can then be naturally extended to the measurement of thermal conduction in nanostructures of other material as well.
Thermal performance of polymers is especially important in applications such as polymer based thermal interface materials, insulating dielectrics for microchips, and polymeric electrolyte membranes in fuel cells. Understanding thermal transport in isolated polymeric nanowires is essential for the design of better polymer nanocomposites. The measurement technique developed in this work will address the need for more sensitive techniques capable of measuring thermal transport through single nanostructures of any material. Such measurements provide invaluable insight into the effects of nanostructuring on thermal properties. The research performed for this project will be integrated into undergraduate and graduate curriculums to emphasize the role of engineering in nanoscale research. The project will also be used to encourage K-12 students to continue onto careers in engineering and science and highlight the importance of mathematics in achieving that goal.
