A microfluidic device with a sandwich structure is proposed to achieve label-free and size-selective separation of tumor cells from pleural effusion. The sandwich structure is a co-flow system incorporating an initial sample layer, an isolation layer and the target sample layer. The isolation layer is used to provide a size-selective interface between the initial sample layer and the isolation layer. The relative magnitude of the inertial lift force and the interfacial lift force at the interface only allows exfoliated tumor cells to migrate out of the sample layer. The high interfacial elastic lift force of the isolation layer also enables the device to be used for pleural effusion samples, whose properties usually vary across a wide range. The target sample layer is used for large migration distances of exfoliated tumor cells in the contraction−expansion array (CEA) channel and high separation efficiency. Cell washing is also achieved with the target sample layer, demonstrating the integration of our device. Experimentally, an optimal flow rate ratio of 1:1:6 was obtained to ensure the stability of the sandwich structure, and the collected fluid was all from the target sample layer. A critical polyethylene oxide (PEO) concentration of the isolation layer (500 ppm, η₀ = 1.37 mPa·s) was then obtained by particle tests. Twenty-micrometer particles were efficiently separated from different viscoelastic samples (PEO concentration changes from 0 to 400 ppm) at this concentration. For the cell test, exfoliated tumor cells from different pleural effusion samples were successfully separated and washed. The separation efficiency of exfoliated tumor cells and blood cells was about 100% and over 90%, respectively. Compared with a conventional co-flow system of two fluids, this device has great advantages in 1) wide applicability for pleural effusion samples of various viscoelasticity and 2) focusing performance. It shows potential for use in medical research and clinical diagnosis of cancer.

提出了一种具有夹心结构的微流体装置，以实现胸膜积液中肿瘤细胞的无标记和大小选择性分离。夹层结构是并流系统，其中包含初始样品层，隔离层和目标样品层。隔离层用于在初始样品层和隔离层之间提供尺寸选择界面。界面处的惯性举升力和界面举升力的相对大小仅允许脱落的肿瘤细胞迁移出样品层。隔离层的高界面弹性提升力也使该设备可用于胸腔积液样品，其性质通常会在很宽的范围内变化。目标样品层用于使脱落的肿瘤细胞在收缩扩展阵列（CEA）通道中具有较大的迁移距离，并具有较高的分离效率。还可以通过目标样品层进行细胞清洗，证明了我们设备的集成性。实验上，为了确保夹层结构的稳定性，获得了最佳流速比1：1：6，并且收集的流体全部来自目标样品层。隔离层的临界聚环氧乙烷（PEO）浓度（500 ppm，收集的液体全部来自目标样品层。隔离层的临界聚环氧乙烷（PEO）浓度（500 ppm，收集的液体全部来自目标样品层。隔离层的临界聚环氧乙烷（PEO）浓度（500 ppm，η ₀  = 1.37毫帕·秒），然后通过粒子试验得到。在该浓度下，从不同的粘弹性样品（PEO浓度从0变为400 ppm）中有效分离了20微米的颗粒。对于细胞测试，成功地分离并洗涤了来自不同胸腔积液样品的脱落的肿瘤细胞。脱落的肿瘤细胞和血细胞的分离效率分别为约100％和超过90％。与传统的两种流体的同流系统相比，该设备具有以下巨大优势：1）广泛适用于各种粘弹性的胸腔积液； 2）聚焦性能。它显示出在医学研究和癌症临床诊断中的潜力。