SUMMARY

The 3-omega technique is a commonly used electrothermal technique to characterize thermal conductivity. While most commonly used to characterize isotropic thin films on substrates, the high accuracy and versatility of the technique can be extended to a broader application space. My dissertation will focus on exploring a few selected applications of thermophysical characterization. 3-omega excels in measuring low thermal conductivities (<1 W/m-K) with high accuracy, making it a prime choice for characterizing gases and amorphous polymers. Using experiments on gas mixtures, a gas sensing technique has been developed that can determine gas concentrations in binary mixtures based on their thermophysical properties. This has been demonstrated using two sensor geometries with sensitivities comparable to other electrothermal techniques, but with a lower power consumption. Using temperature dependent thermal conductivity of polymers, an empirical model is proposed to aid in predicting temperature dependent thermal conductivity of amorphous polymers. The model is based on kinetic theory and accounts for the different vibrational modes in polymers, and depends on only the density, monomer molecular weight, and speed of sound. This empirical model’s predictions were then validated using the 3-omega technique across a range of temperatures.

Finally, experimental techniques to characterize anisotropic thermal conductivity in polymer films and polymer fibers using variants of 3-omega are proposed. A suspended film configuration to measure anisotropic thermal conductivity of polymers will be explored. The experimental guidelines for validity of a simplified 1-D heat transfer model for data analysis are explicitly determined. Furthermore, a suspended microbridge configuration to measure thermal conductivity in crystalline monomer and polymer fibers using a variation of 3-omega is proposed. Temperature-dependent thermal conductivity measurements will be performed, which will aid in understanding the fundamental nature of vibrational transport in crystalline organic fibers.