Ithaca College

Learning about colloidal self-assembly with optical microscopy

Self-assembly does not occur on macroscopic length scales: a pile of bricks will never turn itself into a house. But self-assembly is common on microscopic length scales, particularly in biology. For example, the protein shell, or capsid, of some viruses can spontaneously assemble from a solution of individual protein molecules, even in vitro. Studies of the self-assembly of colloidal particles -- micrometer-sized solid particles dispersed in a liquid solvent --  have led to physical insight into how this happens, as well as ideas for how self-assembly can be harnessed to create useful structures. I will introduce a rapid, high-resolution, three-dimensional imaging technique, digital holographic microscopy (DHM), that may be useful for gaining further insight into colloidal self-assembly. To illustrate the capabilities of DHM, I first discuss precision measurements of the diffusion tensor for clusters of colloidal spheres. I then discuss detailed observations, using DHM, of particle rearrangements within a sphere cluster, something that occurs in the early stages of the nucleation of a colloidal crystal. I also discuss an ongoing undergraduate research project on characterizing self-assembled colloidal fractal aggregates with DHM. Finally, I discuss plans for measuring the capillary interactions between nonspherical colloidal particles at an oil-water interface using optical tweezers and microscopy. Such experiments could lead to new possibilities for self-assembly at liquid-liquid interfaces.

Tues., Dec. 12, 2017
CNS 112 @ 12:10 p.m.

Pizza and Refreshments will be available.
Please bring your own cup.
Remember to Recycle, Reuse, Reduce. 

Individuals with disabilities requiring accommodations should contact the department assistant at jackerman@ithaca.edu. We ask that requests for accommodations be made as soon as possible.