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Atomic Force Microscopy (AFM) and Optical Tweezers (OT) have revolutionised molecular science by measuring picoNewton forces over lengthscales from 1 to 104 Å. Our research focuses on experiments using the technique of OT, but we are also involved in theory and simulation of polymers and soft condensed matter or materials well suited for OT measurements. The OT apparatus is based upon a focused laser beam that is refracted through a micron-sized transparent bead. The refracted rays differ in intensity over the volume of the colloidal bead and exert a force on the bead, drawing it towards the region of highest light intensity. The optical trap generated by the OT serves to both localise a colloidal particle and to measure the small, sub-picoNewton scale forces acting on the particle. The measurements are central to probe and develop new understandings of the energetics and dynamics of small systems, including polymers and colloids.
Edith Sevick graduated from the University of Pittsburgh with a B.S.E. and received her PhD from the University of Massachusetts, Amherst.
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Conventional 19th century thermodynamics have limited our understanding of statistical physics to systems in the thermodynamic limit, at or near equilibrium.
A long, flexible polymer molecule consists of hundreds of thousands of monomeric units. Detailed atomistic simulation of such a molecule and surrounding solvent molecules is not practical if one is interested in detailing the molecule’s dynamics.
More about Hydrodynamic Interactions in Simulations of Flexible Polymers
Mixtures of liquids that phase separate or partially de-mix are ubiquitous. Examples include mixtures that completely de-mix, such as oil and water, as well as partially de-mixed systems, in particular mixtures of colloids and polymers that form liquid-liquid interfaces of ultra-low surface tension.
Research at the forefront of chemistry and biology aims to understand the energetics and dynamics of complex single molecules such as DNA, RNA, and proteins.