Quek Raymond, Le Duc Vinh, Chiam K-H
A*STAR Institute of High Performance Computing, 1 Fusionopolis Way #16-16, Singapore 138632, Singapore.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 May;83(5 Pt 2):056301. doi: 10.1103/PhysRevE.83.056301. Epub 2011 May 2.
Using numerical simulations, we study the separation of deformable bodies, such as capsules, vesicles, and cells, in deterministic lateral displacement devices, also known as bump arrays. These arrays comprise regular rows of obstacles such as micropillars whose arrangements are shifted between adjacent rows by a fixed amount. We show that, in addition to the zigzag and laterally displaced trajectories that have been observed experimentally, there exists a third type of trajectory which we call dispersive, characterized by seemingly random bumpings off the micropillars. These dispersive trajectories are observed only for large and rigid particles whose diameters are approximately more than half the gap size between micropillars and whose stiffness exceeds approximately 500 MPa. We then map out the regions in phase space, spanned by the row shift, row separation, particle diameter, and particle deformability, in which the different types of trajectories are expected. We also show that, in this phase space, it is possible to transition from zigzag to dispersive trajectories, bypassing lateral displacement. Experimentally, this is undesirable because it limits the ability of the device to sort particles according to size. Finally, we discuss how our numerical simulations may be of use in device prototyping and optimization.
我们使用数值模拟方法，研究了在确定性侧向位移装置（也称为凸块阵列）中可变形物体（如胶囊、囊泡和细胞）的分离情况。这些阵列由规则排列的障碍物（如微柱）组成，相邻行之间的排列会有固定量的偏移。我们发现，除了实验中观察到的锯齿形和侧向位移轨迹外，还存在第三种轨迹，我们称之为分散轨迹，其特征是微柱上看似随机的碰撞。仅对于直径约大于微柱之间间隙尺寸一半且刚度超过约500兆帕的大而刚性的颗粒，才会观察到这些分散轨迹。然后，我们绘制了相空间中的区域，该区域由行偏移、行间距、颗粒直径和颗粒可变形性所跨越，其中预期会出现不同类型的轨迹。我们还表明，在这个相空间中，可以从锯齿形轨迹转变为分散轨迹，而无需经过侧向位移。在实验中，这是不理想的，因为它限制了装置根据尺寸对颗粒进行分类的能力。最后，我们讨论了数值模拟在装置原型设计和优化中的用途。
