Seeing Molecules in Color: Science and Commercialization in Resonance Force Microscopy

posted on April 18, 2013 by

Sung Park, CEO Molecular Vista, PO ’81

Will Morrison, PO ’12 

Tuesday, April 23, 2013 4:30 p.m. Millikan Lab – Room 134

We introduce the science behind a new kind of atomic force microscope (AFM).  This “Molecular Resonance Force Microscope” (RFM) measures optical resonances entirely through mechanical vibrations in the AFM tip.  Forces can be measured from resonant e-fields, near field, and stimulated Raman scattering, all concurrent with high resolution topographical data, suggesting potential applications that range from studying the dynamics and structure of bio-molecules to nanoplasmonics.  The presentation will give a short overview of AFM technology to build a foundation for discussing RFM, followed by a description of the new tool and some preliminary data, endeavoring simultaneously to convey some of the unique experience and perspective of doing science and developing an instrument at a small startup.

Coarse-grained Simulations of Ion-Containing Polymers

posted on April 18, 2013 by

Amalie Frischknecht, ‘92  –  Sandia

Tuesday, April 16, 2013 4:30 p.m. Millikan Lab – Room 134

Ionomers are polymers containing a small fraction of covalently bound ionic groups.  They are of interest in electrochemical applications such as electrolytes for batteries and membranes for fuel cells.  In particular, a single-ion conducting polymer electrolyte made of ionomers would be safer and have higher efficiency than currently-used liquid electrolytes.  However, melt ionomeric materials do not have sufficiently high conductivities for practical application.  This is most likely because the ions tend to form aggregates, leading to slow ion transport. A key question is therefore how molecular structure affects the ionic aggregation and ion dynamics. To probe these structure-property relationships, we have performed coarse-grained molecular dynamics simulations of a simple model of ionomers, designed to capture the most important physics in these systems. We find that the ions aggregate into clusters in all of the simulations, but the cluster morphology depends strongly on the polymer architecture. The structure calculated from the MD simulations compares favorably with x-ray scattering data.   Furthermore, the simulations give a detailed picture of the sizes, shapes, and composition of the ionic aggregates, which is difficult to extract from experiment.  We also study the dynamics of the ions, and find that ion transport occurs mainly by cluster rearrangements.  The highest conductivity occurs for ionomers with percolated ionic clusters.

Atomically Thin Photodetectors: The Ideal Semi-Metal vs. the Insurmountable Insulator

posted on April 8, 2013 by

Nathaniel Gabor, MIT

Tuesday, April 9, 2013 4:30 p.m. Galileo- Pryne – Harvey Mudd College

Graphene, an atomically thin sheet of hexagonally oriented carbon, is a zero band gap conductor (semi-metal) that exhibits extraordinary electronic behavior and broadband optical absorption. Hexagonal boron nitride, which shares a similar structure to that of graphene, is a highly insulating electronic material that does not absorb any light in the visible spectrum. By combining graphene and boron nitride into ultrathin vertical stacks, we can fabricate new optoelectronic devices that demonstrate highly sensitive optical response, yet are only as thick as the width of a DNA molecule. In this talk, I will discuss how stacking these atomically thin materials allows us to explore new types of optoelectronic devices that may ultimately lead to more efficient light energy harvesting technologies.

Planet Formation and the Solar System

posted on April 1, 2013 by

Hilke Schlichting, Caltech

Tuesday, April 2, 2013 4:30 p.m. Millikan Lab – Room 134

In my talk, I will discuss recent insights that we have gained into planet formation form our solar system. I will talk about the Kuiper belt, located at the outskirts of our planetary system, which provides a snapshot of earlier stages of planet formation and is therefore an ideal laboratory for testing planet formation theories. I will show how we can use the Kuiper belt size distribution to gain new insights into runaway growth during planet formation and how we can use it to constrain the initial sizes of planetesimals that are the building blocks of planets.