Bonded straight and helical flagellar filaments form ultra-low-density glasses

We study how the three-dimensional shape of rigid filaments determines the microscopic dynamics and macroscopic rheology of entangled semidilute Brownian suspensions. To control the filament shape we use bacterial flagella, which are microns-long helical or straight filaments assembled from flagelli...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2023-04, Vol.120 (17), p.e2215766120-e2215766120
Main Authors: Yardimci, Sevim, Gibaud, Thomas, Schwenger, Walter, Sartucci, Matthew R, Olmsted, Peter D, Urbach, Jeffrey S, Dogic, Zvonimir
Format: Article
Language:English
Subjects:
Biological Physics
Block copolymers
Condensed Matter
Copolymers
Density
Dynamic mechanical properties
Dynamics
Elastic deformation
Filaments
Flagella
Flagellin
Mechanical properties
Modulus of elasticity
Monomers
Physical Sciences
Physics
Rheological properties
Rheology
Rods
Rotational diffusion
Segments
Soft Condensed Matter
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Summary:We study how the three-dimensional shape of rigid filaments determines the microscopic dynamics and macroscopic rheology of entangled semidilute Brownian suspensions. To control the filament shape we use bacterial flagella, which are microns-long helical or straight filaments assembled from flagellin monomers. We compare the dynamics of straight rods, helical filaments, and shape-diblock copolymers composed of seamlessly joined straight and helical segments. Caged by their neighbors, straight rods preferentially diffuse along their long axis, but exhibit significantly suppressed rotational diffusion. Entangled helical filaments escape their confining tube by corkscrewing through the dense obstacles created by other filaments. By comparison, the adjoining segments of the rod-helix shape-diblocks suppress both the translation and the corkscrewing dynamics. Consequently, the shape-diblock filaments become permanently jammed at exceedingly low densities. We also measure the rheological properties of semidilute suspensions and relate their mechanical properties to the microscopic dynamics of constituent filaments. In particular, rheology shows that an entangled suspension of shape rod-helix copolymers forms a low-density glass whose elastic modulus can be estimated by accounting for how shear deformations reduce the entropic degrees of freedom of constrained filaments. Our results demonstrate that the three-dimensional shape of rigid filaments can be used to design rheological properties of semidilute fibrous suspensions.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2215766120