Department of Mechano-Informatics, Graduate School of Information Science and Technology, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8656, Japan.
Langmuir. 2010 Dec 21;26(24):18771-5. doi: 10.1021/la102790w. Epub 2010 Nov 16.
We found that liquid droplets encapsulated by Parylene deposited directly on a liquid surface deformed toward spherical shapes during Parylene deposition. This deformation suggested that the film stress was tensile. We calculated the film stress of such Parylene films by studying the surface mean curvature of the droplet shape and found the film stress measured about 0.7-0.9 MPa tensile. This film stress is of opposite type to that of as-deposited Parylene films deposited on solid substrates, which was compressive. This difference might indicate a profound change of the Parylene polymer due to the use of liquid surface as deposition substrate. The tensile film stress and its effect on the droplet shape also have implications in the fabrication and operation of Parylene microdevices that have encapsulated liquid structures such as microlens or micropumps.
我们发现，聚对二甲苯沉积直接在液体表面上形成的液滴在聚对二甲苯沉积过程中会朝向球形变形。这种变形表明膜应力为拉伸应力。我们通过研究液滴形状的表面平均曲率来计算这种聚对二甲苯薄膜的膜应力，发现所测量的膜应力约为 0.7-0.9MPa 的拉伸应力。这种薄膜应力与沉积在固体基底上的聚对二甲苯薄膜的沉积膜应力相反，后者为压缩应力。这种差异可能表明由于使用液体表面作为沉积基底，聚对二甲苯聚合物发生了深刻的变化。拉伸膜应力及其对液滴形状的影响也对具有封装液体结构（如微透镜或微泵）的聚对二甲苯微器件的制造和操作具有重要意义。
