Center for Bio/Molecular Science and Engineering, U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA.
Anal Bioanal Chem. 2011 May;400(5):1347-58. doi: 10.1007/s00216-011-4872-z. Epub 2011 Mar 30.
A four-electrode impedance-based microfluidic device has been designed with tunable sensitivity for future applications to the detection of pathogens and functionalized microparticles specifically bound to molecular recognition molecules on the surface of a microfluidic channel. In order to achieve tunable sensitivity, hydrodynamic focusing was employed to confine the electric current by simultaneous introduction of two fluids (high- and low-conductivity solutions) into a microchannel at variable flow-rate ratios. By increasing the volumetric flow rate of the low-conductivity solution (sheath fluid) relative to the high-conductivity solution (sample fluid), increased focusing of the high-conductivity solution over four coplanar electrodes was achieved, thereby confining the current during impedance interrogation. The hydrodynamic and electrical properties of the device were analyzed for optimization and to resolve issues that would impact sensitivity and reproducibility in subsequent biosensor applications. These include variability in the relative flow rates of the sheath and sample fluids, changes in microchannel dimensions, and ionic concentration of the sample fluid. A comparative analysis of impedance measurements using four-electrode versus two-electrode configurations for impedance measurements also highlighted the advantages of using four electrodes for portable sensor applications.
已经设计了一种基于四电极阻抗的微流控装置，具有可调灵敏度，可用于未来检测病原体和功能化微颗粒，这些微颗粒专门与微流道表面上的分子识别分子结合。为了实现可调灵敏度，采用流体动力学聚焦在可变流速比下同时将两种流体（高导电性和低导电性溶液）引入微通道，从而限制电流。通过增加低导电性溶液（鞘液）相对于高导电性溶液（样品溶液）的体积流量，可以实现高导电性溶液在四个共面电极上的更集中聚焦，从而在阻抗检测过程中限制电流。分析了设备的流体动力学和电气特性，以进行优化，并解决随后在生物传感器应用中会影响灵敏度和重现性的问题。这些问题包括鞘液和样品液的相对流速的变化、微通道尺寸的变化以及样品液的离子浓度。使用四电极和两电极配置进行阻抗测量的阻抗测量比较分析也突出了使用四电极进行便携式传感器应用的优势。
