Liu Yujia, Kulinsky Lawrence, Shiri Roya, Madou Marc
Department of Materials Science and Engineering, University of California, Irvine, California 92707, USA.
Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697, USA.
Biomicrofluidics. 2022 May 18;16(3):034105. doi: 10.1063/5.0089112. eCollection 2022 May.
Nowadays, centrifugal microfluidic platforms are finding wider acceptance for implementing point-of-care assays due to the simplicity of the controls, the versatility of the fluidic operations, and the ability to create a self-enclosed system, thus minimizing the risk of contamination for either the sample or surroundings. Despite these advantages, one of the inherent weaknesses of CD microfluidics is that all the sequential fluidic chambers and channels must be positioned radially since the centrifugal force acts from the center of the disk outward. Implementation of schemes where the liquid can be rerouted from the disk periphery to the disk center would significantly increase the utility of CD platforms and increase the rational utilization of the real estate on the disk. The present study outlines a novel utilization of elastic membranes covering fluidic chambers to implement inward pumping whereby the fluid is returned from the disk periphery to the center of the disk. When the disk revolves at an angular velocity of 3600 rpm, liquid enters the chamber covered by the elastic membrane. This membrane is deflected upward by liquid, storing energy like a compressed spring. When the angular velocity of the disk is reduced to 180 rpm and thus the centrifugal force is diminished, the elastic membrane pushes the liquid from the chamber inward, closer to the center of the disk. There are two channels leading from the elastic membrane-covered reservoir-one channel has a higher fluidic resistance and the other (wider) has a lower fluidic resistance. The geometry of these two channels determines the fluidic path inward (toward the center of the disk). Most of the liquid travels through the recirculating channel with lower resistance. We demonstrated an inward pumping efficiency in the range of 78%-89%. Elastic membrane-driven inward pumping was demonstrated for the application of enhanced fluid mixing. Additionally, to demonstrate the utility of the proposed pumping mechanism for multi-step assays on the disk, we implemented and tested a disk design that combines plasma separation and inward pumping.
如今，离心微流控平台因其控制简单、流体操作多样以及能够创建自封闭系统，从而将样本或周围环境的污染风险降至最低，而在即时检测中得到更广泛的应用。尽管有这些优点，但CD微流控技术的一个固有弱点是，由于离心力从圆盘中心向外作用，所有连续的流体腔室和通道都必须径向定位。实现液体从圆盘周边重新路由到圆盘中心的方案将显著提高CD平台的实用性，并提高圆盘上空间的合理利用率。本研究概述了一种新颖的利用覆盖流体腔室的弹性膜来实现向内泵送的方法，即流体从圆盘周边返回圆盘中心。当圆盘以3600 rpm的角速度旋转时，液体进入由弹性膜覆盖的腔室。该膜被液体向上偏转，像压缩弹簧一样储存能量。当圆盘的角速度降至180 rpm，从而离心力减小时，弹性膜将腔室内的液体向内推，更靠近圆盘中心。有两条通道从弹性膜覆盖的储液器引出——一条通道的流体阻力较高，另一条（较宽）通道的流体阻力较低。这两条通道的几何形状决定了向内（朝向圆盘中心）的流体路径。大部分液体通过阻力较低的再循环通道流动。我们展示了78%-89%的向内泵送效率。弹性膜驱动的向内泵送被证明可用于增强流体混合。此外，为了证明所提出的泵送机制在圆盘上进行多步检测的实用性，我们实施并测试了一种结合血浆分离和向内泵送的圆盘设计。
