Abstract
The entropic forces on the self-retracting granular chains, which are confined in channels with different widths, are determined. The time dependence of the length of chain remaining in the channel L in (t) is measured. The entropic force is treated as the only parameter in fitting the solution of the nonlinear equation of motion of L in (t) to the experimental data. The dependence of the entropic force on the width of the confining channel can be expressed as a power-law with an exponent of 1.3, which is consistent with the previous theoretical predictions for the entropy loss due to confinement. © 2014 AIP Publishing LLC.