Theory and experiments of transport at channel microband electrodes under laminar flows. 1. Steady-state regimes at a single electrode
Theory and experiments of transport at channel microband electrodes under laminar flows. 1. Steady-state regimes at a single electrode
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DOI：
10.1021/ac070971y
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发表时间：
2007-11-15
影响因子：
7.4
通讯作者：
Thouin, Laurent
中科院分区：
文献类型：
--
作者：
Amatore, Christian;Da Mota, Nicolas;Thouin, Laurent
在过去的几年中，微电极在微流体装置中的集成引起了极大的关注，特别是通过直接或间接电化学技术进行的分析检测。相反，对于这种装置所产生的困难的扩散-对流问题，缺乏一般的理论处理。在这种情况下，我们研究了围合效应和流体动力条件对嵌入微通道内的微带电极监测的稳态安培响应的影响。基于几何参数和水动力参数的数值模拟，在层流条件下确定了几种对流-扩散质量输运模式。通过建立描述所有极限和中间状态的区域图，提出了这些结果的合理化。根据实验条件，模拟了电极在微通道截面上产生的浓度分布。他们的研究使我们能够评估电极探测到的扩散-对流层的厚度，以及溶液在整个微通道截面上再次均匀的下游距离。本文所描述的理论原理的实验验证了本文的结果。在压力驱动下，用二茂铁甲醇水溶液集成在微通道中的微带电极进行了实验。
Integration of microelectrodes in microfluidic devices has attracted significant attention during the past years, in particular for analytical detections performed by direct or indirect electrochemical techniques. In contrast there is a lack of general theoretical treatments of the difficult diffusion-convection problems which are borne by such devices. In this context, we investigated the influence of the confining effect and hydrodynamic conditions on the steady-state amperometric responses monitored at a microband electrode embedded within a microchannel. Several convective-diffusive mass transport regimes were thus identified under laminar flow on the basis of numerical simulations performed as a function of geometrical and hydrodynamic parameters. A rationalization of these results has been proposed by establishing a zone diagram describing all the limiting and intermediate regimes. Concentration profiles generated by the electrode across the microchannel section were also simulated according to the experimental conditions. Their investigation allowed us to evaluate the thickness of the diffusive- convective layer probed by the electrode as well as the distance downstream from which the solution becomes again homogeneous across the whole microchannel section. Experimental checks of the theoretical principles delineated here have validated the present results. Experiments were performed at microband electrodes integrated in microchannels with aqueous solutions of ferrocene methanol under pressure-driven flow.