Motion of a liquid bridge between nonparallel surfaces

作者：Ataei Mohammadmehdi; Tang Tian^*; Amirfazli Alidad^*

来源：Journal of Colloid and Interface Science, 2017, 492: 218-228.

DOI：10.1016/j.jcis.2016.11.093

• Liquid bridge
• Contact Angle Hysteresis
• Contact line pinning
• Drop motion
• Stability
• Nonparallel surfaces
• Surface Evolver
• Capillary bridge

Bulk motion of a liquid bridge between two nonparallel identical solid surfaces undergoing multiple loading cycles (compressing and stretching) was investigated numerically and experimentally. The effects of the following governing parameters were studied: the dihedral angle between the two surfaces (psi), the amount of compressing and stretching (Delta h), and wettability parameters i.e. the advancing contact angle (theta(a)) and Contact Angle Hysteresis (CAH). Experiments were done using various combinations of psi, Delta h and on surfaces with different wettabilities to understand the effect of each parameter individually. Additionally, a numerical model using Surface Evolver software was developed to augment the experimental data and extract information about the shape of the bridge. An empirical function was proposed and validated to calculate the minimum amount of Delta h needed to initiate the bulk motion (i.e. to overcome the initial lag of the motion in response to the compressing of the bridge), at a given dihedral angle psi. The effect of governing parameters on magnitude and precision of the motion was investigated. The magnitude of the motion was found to be increased by increasing psi and Delta h, and/or by decreasing theta(a) and CAH. We demonstrated the possibility of modulating the precision of the motion with theta(a). Additionally, it was shown that the magnitude of the motion (in one loading cycle) increases after each loading cycle, if the contact lines depin only on the narrower side of the bridge during compressing and only on the wider side during stretching (asymmetric depinning). Whereas, depinning on both sides of the bridge (symmetric depinning) reduced the magnitude of bridge motion in each cycle under cyclic loading. A larger psi was found to convert symmetric depinning into asymmetric depinning. These findings not only enhance the understanding of bridge motion between nonparallel surfaces, but also are beneficial in controlling magnitude, precision, and lag of the motion in practical applications.

• 出版日期2017-4-15