Volume 84, Number 6, December 2008
Article Number 68006
Number of page(s) 5
Section Interdisciplinary Physics and Related Areas of Science and Technology
Published online 12 January 2009
EPL, 84 (2008) 68006
DOI: 10.1209/0295-5075/84/68006

Lock and key model system

P.-M. König, R. Roth and S. Dietrich

Max-Planck-Institut für Metallforschung - Heisenbergstr. 3, 70569 Stuttgart, Germany, EU and Institut für Theoretische und Angewandte Physik, Universität Stuttgart - Pfaffenwaldring 57, 70569 Stuttgart, Germany, EU

received 18 September 2008; accepted in final form 19 November 2008; published December 2008
published online 12 January 2009

The lock and key concept is important for various biological and colloidal self-assembly processes. We study the basic and common underlying mechanisms within a model system which consists of a biaxial elliptical key immersed in a hard-sphere solvent and a smooth lock substrate into which the key can fit geometrically. If the rotational degrees of freedom of the key are constrained, the key faces on its way into the lock a free-energy barrier too high to be overcome by thermal fluctuations. However, if the key is unconstrained, the range of the effective attraction of the lock is significantly increased so that the key can, guided by a complex interplay of entropic forces and torques, successfully follow a trajectory into the lock which avoids the free-energy barrier.

82.70.Dd - Colloids.
61.20.Gy - Theory and models of liquid structure.

© EPLA 2008