School of Engineering, University of Edinburgh, King's Buildings, Edinburgh, UK.
Lab Chip. 2017 Sep 26;17(19):3318-3330. doi: 10.1039/c7lc00785j.
We uncover anisotropic permeability in microfluidic deterministic lateral displacement (DLD) arrays. A DLD array can achieve high-resolution bimodal size-based separation of microparticles, including bioparticles, such as cells. For an application with a given separation size, correct device operation requires that the flow remains at a fixed angle to the obstacle array. We demonstrate via experiments and lattice-Boltzmann simulations that subtle array design features cause anisotropic permeability. Anisotropic permeability indicates the microfluidic array's intrinsic tendency to induce an undesired lateral pressure gradient. This can cause an inclined flow and therefore local changes in the critical separation size. Thus, particle trajectories can become unpredictable and the device useless for the desired separation task. Anisotropy becomes severe for arrays with unequal axial and lateral gaps between obstacle posts and highly asymmetric post shapes. Furthermore, of the two equivalent array layouts employed with the DLD, the rotated-square layout does not display intrinsic anisotropy. We therefore recommend this layout over the easier-to-implement parallelogram layout. We provide additional guidelines for avoiding adverse effects of anisotropy on the DLD.
我们揭示了微流控确定性横向位移（DLD）阵列中的各向异性渗透性。DLD 阵列可以实现基于大小的双模态高分辨率微粒子分离，包括生物粒子，如细胞。对于给定分离尺寸的应用，正确的设备操作要求流动保持固定角度流向障碍物阵列。我们通过实验和格子玻尔兹曼模拟证明，细微的阵列设计特征会导致各向异性渗透性。各向异性渗透性表示微流道阵列内在的诱导非期望横向压力梯度的趋势。这可能导致倾斜流动，从而导致临界分离尺寸的局部变化。因此，粒子轨迹可能变得不可预测，并且该设备对于所需的分离任务毫无用处。对于障碍物柱之间轴向和横向间隙不相等且柱形状极不对称的阵列，各向异性会变得更加严重。此外，在 DLD 中使用的两个等效的阵列布局中，旋转正方形布局不显示内在的各向异性。因此，我们建议使用此布局而不是更易于实现的平行四边形布局。我们提供了避免 DLD 中各向异性不利影响的其他指导方针。
