Colloquium

Colloidal Condensed Matter

Vinothan N. Manoharan
Assistant Professor of Physics and Chemical Engineering
Harvard University
Wednesday, April 11, 2007
Higgins 310, 4 pm

The very first Nobel Prize went to J. H. van 't Hoff for his discovery that dilute suspensions of small particles in a solvent obey the ideal gas equation of state. Since that time it has been established that suspensions of particles -- colloids -- can also form liquids, crystals, and even glassy phases. Because the particles are much larger than atoms or molecules, they behave classically, and both the structure and dynamics of the phases they form can be studied experimentally, in situ, at room temperature. In the last two decades, experiments on these systems have revealed many universal physical principles governing the formation of condensed phases.

In this talk I will discuss experiments on new, "complex" colloidal systems, where we use chemistry and polymer physics to build particles with precisely controlled interactions. We use these particles to study the properties of matter under confinement. We find, for example, that isotropic compression of a small group of spherical particles leads to structures that resemble molecules. To study these systems we use optical microscopy, light scattering, and a relatively new imaging method called digital holographic microscopy, which allows us to see all the particles in three dimensions, in real space and real time.