Role of Vertical Component of Surface Tension of the Droplet on the Elastic Deformation of PDMS Membrane
Role of Vertical Component of Surface Tension of the Droplet on the Elastic Deformation of PDMS Membrane
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DOI：
10.1163/156856108x305732a
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发表时间：
2008-01
影响因子：
2.3
通讯作者：
Ying-Song Yu;Zhenyu Yang;Ya-pu Zhao
中科院分区：
文献类型：
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作者：
Ying-Song Yu;Zhenyu Yang;Ya-pu Zhao
聚二甲基硅氧烷（PDMS）广泛应用于芯片实验室和微全分析系统（μ-TAS）中，其润湿和电润湿行为在这些器件中具有重要意义。由于PDMS是一种软质高分子材料，液滴对PDMS膜的弹性变形不能忽略，这是由于液-气界面张力的垂直分量，而液-气表面张力的垂直分量又被PDMS膜内部的应力分布所平衡。这种弹性变形和应力分布不仅影响接触角的准确测量，而且影响器件的微流控行为。利用ANSYS软件，数值模拟了刚性基底上PDMS膜在气液界面张力作用下的弹性变形和应力分布。研究发现，由于施加了直径为2.31 mm的液滴，PDMS膜的垂直弹性变形量为几十nm量级，这对于芯片实验室和μ-TAS不再是可以忽略的。PDMS膜的纵向弹性变形随膜厚的增加而增大，存在一个饱和膜厚，可视为半无限膜厚，当膜厚大于或等于饱和膜厚时，纵向弹性变形达到极限值。
Poly(dimethylsiloxane) (PDMS) has been widely used in lab-on-a-chip and micro-total analysis systems (μ-TAS), thus wetting and electrowetting behaviors of PDMS are of great importance in these devices. PDMS is a kind of soft polymer material, so the elastic deformation of PDMS membrane by a droplet cannot be neglected due to the vertical component of the interfacial tension between the liquid and vapor, and this vertical component of liquid–vapor surface tension is also balanced by the stress distribution within the PDMS membrane. Such elastic deformation and stress distribution not only affect the exact measurement of contact angle, but also have influence on the micro-fluidic behavior of the devices. Using ANSYS code, we simulated numerically the elastic deformation and stress distribution of PDMS membrane on a rigid substrate due to the liquid–vapor surface tension. It is found that the vertical elastic deformation of the PDMS membrane is on the order of several tens of nanometers due to the application of a droplet with a diameter of 2.31 mm, which is no longer negligible for lab-on-a-chip and μ-TAS. The vertical elastic deformation increases with the thickness of the PDMS membrane, and there exists a saturated membrane thickness, regarded as a semi-infinite membrane thickness, and the vertical elastic deformation reaches a limiting value when the membrane thickness is equal to or thicker than such saturated thickness.