Contact angle hysteresis a first analysis of the noise of the creeping motion of the contact line

We study the force exerted on a fiber by a moving liquid interface. We show that the noise of this force should correspond to the pinning-depinning process (or stick and slip) of the contact line on defects (which can be physical defects as roughness or chemical heterogeneities). For fibers with a low concentration of defects, we find experimentally that the contact angle hysteresis y(cos 0, - cos 02 is proportional to - h2/So, where h is the fluctuation of this force and SO the average spreading parameter.