Work needed to force the water-air interface down in the re-entrant structured capillary pore

The re-entrant structure of the membrane surface has attracted researchers' attention recently, due to its ability to make the membrane surface more wetting resistant-either in water or in liquids of low surface tension. The underlying principle of this approach is that an energy barrier has to be overcome when the transition occurs from the Cassie Baxter state to the Wenzel state of the rough membrane surface, which prevents the passage of liquid through the membrane pore. In this work, the energy barrier was evaluated for the cone-shaped pore based on Young's theory of the capillary force. It was found that the energy barrier is enhanced by increasing the angle of the apex of the cone, the pore length, and the contact angle. The effects of the first two geometrical factors, the angle of apex of cone and pore length, are much stronger than the effect of the contact angle. It is believed that this work will offer a guideline for the rational membrane design to reduce, and even prevent, the pore wetting of membranes, particularly for oil/water separation and membrane distillation.

Automated summary

The re-entrant structure of the membrane surface has been a focus of recent research due to its ability to enhance the wetting resistance of the membrane. This study evaluated the energy barrier of a cone-shaped pore and found that it can be enhanced by increasing the angle of the apex of the cone, the pore length, and the contact angle. The effects of the angle and pore length were found to be stronger than the contact angle. The findings of this study provide guidance for the rational design of membranes to reduce pore wetting, particularly for applications such as oil/water separation and membrane distillation.