Entropic force on a Polymer

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




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

yellow ball Dimensional analysis suggests:

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


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

yellow ball Comparing the two expressions yields

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