Theoretical Problems in Soft Matter and Biological Materials

Harvard University, Cambridge MA

Investigators

Abstract

TECHNICAL SUMMARY: This awards supports research and education in statistical mechanics and applications to problems in soft matter and biological materials. An outstanding problem in condensed matter and materials science is the behavior of crumpled surfaces at high nonlinearity, or Foppl-von Karman number. The PI aims to develop a theory of the deformations and crumpling of amorphous shells that can be created from, e.g., genetically engineered spider silk proteins condensed onto water droplets. The PI will consider what happens when these shells, described by a Young modulus and a bending rigidity, are deformed by a point force or by osmotic pressure. He hopes to demonstrate that thermal fluctuations lead to extremely large deviations from the classical predictions of the nonlinear Foppl-von Karman equations. In addition, the PI will explore the finite-temperature shear denaturation pathways of the DNA hybrids that hold together artificial nanoparticle assemblies, with an emphasis on the effects of sequence heterogeneity. Statistical methods will be applied as well to understand anomalous genome unzipping landscapes for temperate bacteriaphages such as phage lambda, with the hope of predicting features of unknown bacterial hosts of newly discovered viral genomes. The PI plans to develop a theory of ordered crystalline and smectic states created from diblock copolymers on surfaces with a spatially varying Gaussian curvature, with the aim of better understanding the limitations of soft lithography on curved surfaces. NON-TECHNICAL SUMMARY: This award supports theoretical research and education in statistical physics and its application to problems inspired by biology and soft materials. The PI aims to understand: how amorphous shells deform and crumble, what can be learned from "unzipping" the double strands of a DNA molecule or otherwise inducing a change in the structure of a DNA molecule or DNA nanoparticle assembly, and the physics of crystals confined to curved surfaces and how it differs from ordinary crystals. Theoretical methods developed in the course of research can have a strong impact on the understanding and creation of new materials, some of biological origin. Powerful new experimental methods have led to new questions and challenges particularly in soft condensed matter and in biological systems that can be answered by the synergy between theory and experiment. Understanding the mechanical properties of amorphous shells of colloidal particles or proteins has implications for creating robust drug delivery systems, where colloidal shells act as a kind of armor plating. DNA-Gold nanoparticle assemblies have detection applications for the biological sciences. A comprehensive theory of crystals on curved surfaces could help guide the construction of new materials.