Department of Electrical Engineering, Lahore University of Management Sciences, Lahore, Pakistan.
Thunderbird, Arizona State University, Tempe, USA.
Sci Rep. 2022 Jan 20;12(1):1066. doi: 10.1038/s41598-022-04917-5.
Microfluidic cytometers based on coulter principle have recently shown a great potential for point of care biosensors for medical diagnostics. Here, we explore the design of an impedimetric microfluidic cytometer on flexible substrate. Two coplanar microfluidic geometries are compared to highlight the sensitivity of the device to the microelectrode positions relative to the detection volume. We show that the microelectrodes surface area and the geometry of the sensing volume for the cells strongly influence the output response of the sensor. Reducing the sensing volume decreases the pulse width but increases the overall pulse amplitude with an enhanced signal-to-noise ratio (~ max. SNR = 38.78 dB). For the proposed design, the SNR was adequate to enable good detection and differentiation of 10 µm diameter polystyrene beads and leukemia cells (~ 6-21 µm). Also, a systematic approach for irreversible & strong bond strength between the thin flexible surfaces that make up the biochip is explored in this work. We observed the changes in surface wettability due to various methods of surface treatment can be a valuable metric for determining bond strength. We observed permanent bonding between microelectrode defined polypropylene surface and microchannel carved PDMS due to polar/silanol groups formed by plasma treatment and consequent covalent crosslinking by amine groups. These experimental insights provide valuable design guidelines for enhancing the sensitivity of coulter based flexible lab-on-a-chip devices which have a wide range of applications in point of care diagnostics.
基于库尔特原理的微流控细胞仪最近在医疗诊断的即时检测生物传感器方面显示出巨大的潜力。在这里，我们探索了在柔性衬底上设计阻抗式微流控细胞仪。比较了两种共面微流控几何形状，以突出设备对微电极相对于检测体积的位置的灵敏度。我们表明，微电极表面积和细胞的检测体积的几何形状强烈影响传感器的输出响应。减小检测体积会减小脉冲宽度，但会增加整体脉冲幅度，同时提高信号噪声比（最大 SNR=38.78 dB）。对于所提出的设计，信噪比足以实现对 10 µm 直径聚苯乙烯珠和白血病细胞（6-21 µm）的良好检测和区分。此外，本工作还探索了在构成生物芯片的薄柔性表面之间建立不可逆且强键合强度的系统方法。我们观察到由于表面处理的各种方法导致的表面润湿性变化可以作为确定键合强度的有价值的指标。我们观察到由于等离子体处理形成的极性/硅醇基团和随后的胺基团的共价交联，在微电极定义的聚丙烯表面和微通道雕刻的 PDMS 之间形成了永久性键合。这些实验见解为增强基于库尔特的柔性片上实验室设备的灵敏度提供了有价值的设计指南，该设备在即时检测诊断中有广泛的应用。
