基于PDMS和玻璃材料的毛细管被动阀临界压力分析

Burst pressure of capillary burst valve based on glass and PDMS

针对现有的数值仿真方法不能够准确地计算矩形截面毛细阀用亲水性很好的玻璃作盖板时的临界压力,提出了一种分析复合壁面毛细管被动阀临界压力的方法。使用Surface Evolver(SE)自由软件,通过设置和实际流动相符的边界条件,并监测在扩张段入口处接触角的变化范围,实现了对由玻璃盖板和PDMS微通道构成的被动阀的临界压力的计算。此时,接触线应该设置为可以进入到扩张段的侧壁上,而不能固定在扩张段入口处。对于深度为25μm,宽深比为2,4,8,16的毛细管被动阀,得到的临界压力分别为0.77,0.45,0.33,0.24 kPa。仿真结果和转台实验结果基本相符,证实了SE方法的有效性。文中分析了接触角对毛细阀有效性的影响,指出当通道和平板材料的接触角之和大于90°时,毛细阀才能控制流动。

As the current simulation methods for capillary burst valves can not exactly calculate the burst pressure when the passive valve is limited by a glass flat cover with good hydrophilicity,a method to analyze the critical pressure of the passive value was proposed.The Surface Evolver（SE） was used to simulate the burst pressure of the microvalve composed of a glass cover and PDMS microchannels by setting the properly boundary conditions and monitoring the variation of the contact angle at the entrance of expansion section.In simulation,the liquid contact line should be set up the entrance of expansion section and come into the expansionary walls that connect the glass cover.Experiments show that the capillary burst pressures are 0.77,0.45,0.33 and 0.24 kPa,respectively,for the microvalves with the depth of 25 μm and the aspect of 2,4,8 and 16.The obtained simulation data are well in agreement with that obtained by a rotating platform.The effect of the contact angle for the capillary burst valve was also discussed,which points out that the valves do work until the sum of the contact angles on both the flat cover and the channel wall is greater than 90°.