Hysteresis

In general, hysteresis describes the behavior of a system in which an output variable is dependent on an input variable and also on the previous state of the output variable. In such a system, the output variable assumes different values when the input variable increases from when it decreases.

Background

Hysteresis occurs with the dynamic contact angle, as the contact angle usually assumes different values in the course of wetting (advancing angle) from de-wetting (receding angle).

 

Surfaces with a higher degree of inhomogeneity (both topographically and chemically) usually have a stronger hysteresis. The degree of hysteresis is also associated with a force of adhesion between the liquid and the solid surface.

Measurement of advancing angle
Measurement of receding angle