Jindal Rohit, Plawsky Joel L, Cramer Steven M
Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
Langmuir. 2005 May 10;21(10):4458-63. doi: 10.1021/la047463t.
The ability to pattern different polymers in microfluidic channels is indispensable for the development of multifunctional, "lab-on-a-chip" devices. A simple method, based on the concept of selective filling, is described for introducing different polymers at defined locations in microfluidic channels. Selective filling is based on the difference in the free energy of filling between an open and a covered part of the channel. It is implemented by covering part of the channel, along its length, with a temporary poly(dimethylsiloxane) (PDMS) slab. Preferential filling is related to the contact angle of the liquid solution on the chip surface. An expression for the critical contact angle is derived, and its dependence on the geometry of the channel is established. It is further shown that a trapezoidal geometry of the cross-section of the channel is optimal for selective filling. Experimental verification of the applicability of the critical contact angle in predicting selective filling is demonstrated by introducing liquid prepolymer solutions of different contact angles in the glass channel that was etched using photolithography and wet etching. Finally, patterning of two different polymers along the axial direction of the microfluidic channel is demonstrated using this selective filling technique.
在微流控通道中对不同聚合物进行图案化的能力对于多功能“芯片实验室”设备的开发至关重要。本文描述了一种基于选择性填充概念的简单方法，用于在微流控通道的特定位置引入不同的聚合物。选择性填充基于通道开放部分和覆盖部分之间填充自由能的差异。它通过沿通道长度用临时聚二甲基硅氧烷（PDMS）平板覆盖通道的一部分来实现。优先填充与液体溶液在芯片表面的接触角有关。推导了临界接触角的表达式，并确定了其对通道几何形状的依赖性。进一步表明，通道横截面的梯形几何形状对于选择性填充是最佳的。通过在使用光刻和湿法蚀刻工艺蚀刻的玻璃通道中引入具有不同接触角的液体预聚物溶液，证明了临界接触角在预测选择性填充方面适用性的实验验证。最后，使用这种选择性填充技术展示了沿微流控通道轴向对两种不同聚合物进行图案化的过程。
