Entropic force on a Polymer

 Several micro-manipulation techniques, such as Atomic Foce Microscopy, measure forces required to unravel specific (mostly bio-) polymers.

 What is the entropic force on a uniform (phantom or self-avoiding) polymer?

 Dimensional analysis suggests:

 Work done in moving the tip (with polymer attached) away from the surface is

-

 This work can be related to the difference in free energies, as

 Comparing the two expressions yields

"Entropic force of polymers on a cone tip," M. F. Maghrebi, Y. Kantor, M. Kardar, EPL 96, 66002 (2011)

Next (Phantom polymers) Outline Casimir force in QED Thermal Casimir Membranes & more Scale-invariant shapes Entropic polymer force Phantom polymers Self-avoinding polymers Summary