Technical Abstract: The proposed program is a fundamental study of the random pinning problem using model colloidal systems. In this program, the PI proposes to apply the well-known concept of Campbell penetration depth in type-II superconductivity to establish a new experimental paradigm in colloid physics, called "stress screening", in studying the random pinning problem. The proposed experiments include measurements of Campbell length in a model 1D colloidal chains and 2D colloidal lattices. The experiments will pave the way for the experimental exploration of the physics of random-manifold regime proposed in the theoretical models of Bragg glass. The results of this program will shed new light to the random pinning problem and the new state of matter Bragg glass, thus will be of fundamental importance for superconductivity, condensed matter physics, surface science, and solid-state mechanics. This project will provide advanced training for graduate and undergraduate students in nanofabrication, video microscopy, and novel optical technique. These skills will prepare students for their future careers in the emerging areas of nanotechnology-based soft matter physics, biophysics, and materials sciences.
The proposed program is a fundamental study of the random pinning problem in condensed matter physics using colloidal particles as a model system. The random pinning problem is related to many condensed matter systems. For example, in superconductivity, how a superconducting cable carrying electric current without dissipation is determined by how the magnetic flux lines are pinned by atomic impurities; in nanobiotechnology, how a DNA is driven through a nanopore, important for a DNA sequencing technology, is related to how the charges on a DNA molecule interact with the rough charged surface of the nanopore. The colloidal matter system has the distinct advantage that each particle can be observed in real time using optical microscope and their dynamics can be studied using digital video microscopy, thereby providing unparallel insight into the intricate interplay between interactions, thermal fluctuations and random disorder. This project will provide advanced training for graduate and undergraduate students in nanofabrication, video microscopy, and novel optical technique. These skills will prepare students for their future careers in the emerging areas of nanotechnology-based soft matter physics, biophysics, and materials sciences.
" Xinsheng Sean Ling Department of Physics, Brown University, Providence, Rhode Island 02912 Intellectual Merit: The science goal of this project is to develop a model 1D and 2D colloidal matter system for studying nonequilibrium statistical mechanics of systems with random pinning. Driven dynamics of interacting systems with random pinning is relevant to a broad range of condensed matter systems, from vortices in superconductors to DNA translocation in nanopores. During the past three years, the PI and his students explored the driven dynamics of 1D and 2D colloidal matter using direct video microscopy and electrical detection methods. The research results include a new test of Schrodinger’s first-passage theory, understanding of defects in colloidal lattices, and nonlinear electrophoretic motion in strong electric field. These studies represent new directions in the studies of nonequilibrium statistical mechanics and discovered new phenomena which may provide new sensing technologies for soft matter and biological systems. Broader Impact: In addition to potential technological spin-offs of the research findings, this project provided excellent training opportunities for Ph.D. and high school students.
