Microfluidic electrical impedance flow cytometry is now a well-known and established method for single-cell analysis. Given the richness of the information provided by impedance measurements, this non-invasive and label-free approach can be used in a wide field of applications ranging from simple cell counting to disease diagnostics. One of its major limitations is the variation of the impedance signal with the position of the cell in the sensing area. Indeed, identical particles traveling along different trajectories do not result in the same data. The positional dependence can be considered as a challenge for the accuracy of microfluidic impedance cytometers. On the other hand, it has recently been regarded by several groups as an opportunity to estimate the position of particles in the microchannel and thus take a further step in the logic of integrating sensors in so-called “Lab-on-a-chip” devices. This review provides a comprehensive overview of the physical grounds of the positional dependence of impedance measurements. Then, both the developed strategies to reduce position influence in impedance-based assays and the recent reported technologies exploiting that dependence for the integration of position detection in microfluidic devices are reviewed.

中文翻译：

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微流电阻抗流式细胞仪中颗粒和细胞的位置依赖性：起源，挑战和机遇。

现在，微流体电阻抗流式细胞仪是一种众所周知的单细胞分析方法。考虑到阻抗测量提供的信息丰富，这种无创且无标签的方法可用于从简单细胞计数到疾病诊断的广泛应用领域。其主要限制之一是阻抗信号随单元在感应区域中的位置而变化。实际上，沿不同轨迹行进的相同粒子不会得到相同的数据。位置依赖性可被视为对微流控阻抗细胞仪准确性的挑战。另一方面，最近，几个小组将其视为一种机会来估计微粒在微通道中的位置，从而在将传感器集成到所谓的“芯片实验室”设备中的逻辑上又迈出了一步。本文对阻抗测量的位置依赖性的物理基础进行了全面概述。然后，回顾了在基于阻抗的测定中减少位置影响的已开发策略和利用微流体设备中位置检测集成依赖性的最新报道技术。