UC Berkeley

The bulk properties of materials and biological systems depend on their microscale behavior. This is intuitive to chemists who are used to thinking of molecular constituents dictating chemical properties at the macroscale. This bottom-up understanding of materials can be extended to mechanical properties, such as Young's modulus, catastrophic failure modes, which can begin as nanoscale void formation, and polymer chain deformations that occur during mechanical loading. Such fundamental mechanical properties are also crucial in biology, where the viability of an organism is dependent on cell function and behavior. For example, tumorigenesis and metastasis of cancer depends on the ability of a cancerous cell to generate traction forces and move through the body.

This dissertation details recent developments on the tetrapod quantum dot (tQD) as a fluorescence stress probe. The nanometer size and optical properties of the tQD make it uniquely suitable for studying forces and mechanisms of mechanical deformation at the smallest length scales. First, background is provided on colloidal semiconductor quantum dots in general and the tetrapod in particular. Second, development and application of the tQD in synthetic polymer materials is discussed. Third, applications of the tQD as a sensor for cellular biophysics are demonstrated. Finally, further characterization of single tQD properties and future studies are discussed and proposed.