Toward a 3D Physical Model of Diffusive Polymer Chains

Recent studies in polymer physics have created macro-scale analogs to solute microscopic polymer chains like DNA by inducing diffusive motion on a chain of beads. These bead chains have persistence lengths of O(10) links and undergo diffusive motion under random fluctuations like vibration. We present a bead chain model within a new stochastic system: an air fluidizing bed of granular media. Bead chains are buffeted randomly by the multiphase flow of the shifting grains and the coalescing bubbles. We thermalize bead chains of various lengths at different fluidizing airflow rates, while X-ray imaging captures the chains' dynamics within the media. With modern 3D printing techniques, we can better represent complex polymers by geometrically varying bead connections and their relative strength, mimicking the variable stiffness between adjacent nucleotide pairs of DNA. By attaching magnets to the bead chains' ends, we can also pin the chain into loops if the ends meet under fluctuation as in DNA looping.