W-shaped meniscus from thin polymer films in microchannels

Transient meniscus formation in microchannels reveals that a 'W'-shaped meniscus forms at early times for relatively large channel size and lower annealing temperature. This phenomenon is opposed to the uniformly curved meniscus, which has been believed to be dominant for transients. This formation is attributed to the competition between the Laplace pressure and viscous resistance. Conditions are given under which the W-shaped meniscus forms, which is shown to represent the experimental data satisfactorily. During transients, the contact angle is found to be maintained at its equilibrium value.