Speaker
Description
Active forces provide a powerful means of controlling the structure and dynamics of soft and biological polymers. In this talk, I will discuss our recent work on how the spatial organization of activity controls polymer conformation, mechanics, transport, and topology. We first consider active polymers with distributed propulsion, where the interplay between activity and polymer connectivity leads to activity-induced swelling, collapse, and enhanced transport. I will then focus
on a flexible polymer driven by a single localized polar motor, where the position of the active site emerges as a key control parameter. Motors near the chain ends generate predominantly unidirectional tension, promoting polymer stretching and directed motion, whereas an interior motor transmits force toward both ends, producing contour accumulation and compression. At intermediate activity, this localized compression drives backfolding, self-entanglement, and a pronounced
increase in knot formation. Remarkably, a single motor is sufficient to nucleate knots, which subsequently migrate along the polymer backbone and are released at the free end, establishing a nonequilibrium cycle of topological creation and removal. Together, these results demonstrate how spatially localized active forces can be used to regulate polymer architecture and transport, providing a minimal physical framework relevant to motor-driven organization of biological polymers such as chromatin and cytoskeletal filaments.
S. Jaiswal et. al, “Critical role of the motor density and distribution on polar active polymers” Physical Review Research (2026)