NSF-Europe: Mechanical Properties of Thin-Film Active Materials

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This project funds the US component of an international collaboration between theorists (University of Massaschusetts, Amherst and the Vrije Universiteit in Amsterdam) and experimentalists (University of California, Irvine and the Vrije Universiteit) to study the material properties of biopolymer networks (F-actin) driven by molecular motors. A better fundamental understanding of the material properties of such systems will help to elucidate the materials properties of the cytoskeleton of eukaryotic cells and facilitate the development of novel, biomimitic materials based on cytoskeletal design motifs. In order to both enable the direct observation of the strain field within the network and to draw inferences from the data regarding the cytoskeleton coupled to the lipid membrane of the cell, these experiments will be performed at the surface of a Langmuir monolayer. To develop the required experimental techniques the collaboration involves experts in both F-actin/molecular motors and Langmuir monolayers. Their experimental work will be done in close collaboration with theorists who are developing a new model of the deformation properties of semiflexible gels. The theorists will work closely with their experimental colleagues to further refine microrheology techniques for use in this system (and, by extension, in intracellular microrheological experiments) as well as to develop predictive models of the relationship between the microstructure and motor activity of the active gel and its rheological properties. There will be a strong educational component of this work, as it will serve as the training ground for a new breed of scientists that are capable of working across the disciplines of physics and biology. Young scientists at all levels of their career, undergraduate, graduate students, and post-doctoral researchers, will be involved in the project.This project funds the US component of a joint US-European collaboration. One of the exciting efforts underway in nanoscience is the adaptation of bio-machines or bio-materials for technological applications. To accomplish this, one must first understand the physical properties underlying the function of the biological systems. This research focuses on a particular subset of biomaterials: active materials. In active materials, the response of the material to external forces or distortions depends on the state of internal active elements, such as motor proteins. This project will systematically study an active material consisting of three parts: a surfactant monolayer at the air-water interface; a network of protein fibers, known as actin, that are attached to the monolayer; and motor proteins connected to the actin network. Central to this project is the interaction between theory and experiment, as new techniques for making local measurements of mechanical properties need to be developed. There will be a strong educational component of this work, as it will serve as the training ground for a new breed of scientists that are capable of working across the disciplines of physics and biology. Young scientists at all levels of their career, undergraduate, graduate students, and post-doctoral researchers, will be involved in the project.