We report an entropic pulling force that commonly occurs in systems with molecular or macroscopic binding. A particle binding to an object produces an entropic pulling force on the object because the bound particle tends to escape from this object to gain more entropy. This entropic pulling effect leads to an entropic force of ~ , where is the Boltzmann constant, T is temperature, and is the binding length. We validate this entropic pulling effect through simulations and experiments. In macroscopic experiments, a particle bound to a bead-chain on a vibration platform, where mechanical vibration mimics thermal noise, produces an entropic force. In single-molecule magnetic-tweezers experiments, multivalent ions binding to DNA exert an entropic force to enlarge the DNA’s diameter, detected through precise measurement of DNA twist change and twist-diameter coupling. The reported entropic force has biological and technological implications. Cells may utilize this entropic force to disassemble protein aggregates in neurodegenerative diseases, while engineered molecular machines could harness it to exert controlled force.
Read more at Nature Communications:
https://www.nature.com/articles/s41467-025-64670-x
Photo caption:
a Bond-length distribution for a harmonic bond. The peak location, , is larger than the spring equilibrium length, . b Entropic force and . c Simulation snapshot of a membrane with a bound particle. d The average z-position of different beads on the membrane. The peak is located at the anchor. e Entropic force and deformation at the anchor. f Snapshot of a chain with particle binding in a 2D simulation. g Average chain conformation shows a hump at the anchor for . h Entropic pulling force at the anchor. i Simulation snapshot of a rod with particle binding. j Entropic force and deformation at the anchor. k Deformations of different beads on the rod. For better viewing, the deformations on a rod are transformed to the deformations on a flat surface. The peak is located at the anchor. l, m Entropic force at the anchor when a harmonic or Coulomb potential is applied for the binding at the anchor.
30 Oct 2025
