MAE Seminar: Cell Mechanics, Revisited

Details

MAE Seminar: Cell Mechanics, Revisited
Date: April 21, 2026
Time: 12:50 PM Location: MAE-A 303

Dr. David Weitz
Professor
John A. Paulson School of Engineering and Applied Sciences
Harvard University

Abstract
The mechanical properties of a cell are determined primarily by an interpenetrating network of biopolymers. By using magnetic tweezers to pull a particle through the cytoplasm of a cell, we show that the particle exhibits unusual behavior: Its velocity is independent of the force pulling the particle. This velocity can be used as a probe of the mechanics within the cell and of the contributions of the different biopolymer networks. We suggest that this behavior requires a different constitutive equation to describe the rheology of the cell. We also examine the properties of vimentin intermediate filaments and suggest that their behavior is reminiscent of a self-assembled structure formed by surfactants, a worm-like micelle. This perspective accounts for many properties that are observed for vimentin intermediate filament networks. Vimentin also forms phase-separated liquid droplets that are a precursor to formation of the filament network. This is the first observation of phase separation of proteins in a cell leading to an ordered structure with a mechanical function.

Biography
Weitz received his PhD in physics from Harvard University and then joined Exxon Research and Engineering Company, where he worked for nearly 18 years. He then became a professor of physics at the University of Pennsylvania and moved to Harvard at the end of the last millennium as professor of physics and applied physics. He leads a group studying soft matter science with a focus on materials science, biophysics, microfluidics and flow in porous media. Several startup companies have come from his lab to commercialize research concepts.

Faculty Host: Dr. Xin Tang