Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, USA.
Anal Chem. 2010 Mar 1;82(5):1659-68. doi: 10.1021/ac901066p.
Amperometric detection at microelectrodes in lab-on-a-chip (LOAC) devices lose advantages in signal-to-background ratio, reduced ohmic iR drop, and steady-state signal when volumes are so small that diffusion fields reach the walls before flux becomes fully radial. Redox cycling of electroactive species between multiple, closely spaced microelectrodes offsets that limitation and provides amplification capabilities. A device that integrates a microchannel with an individually addressable microband electrode array has been used to study effects of signal amplification due to redox cycling in a confined, static solution with different configurations and numbers of active generators and collectors. The microfabricated device consists of a 22 microm high, 600 microm wide microchannel containing an array of 50 microm wide, 600 microm long gold microbands, separated by 25 microm gaps, interspersed with an 800 microm wide counter electrode and 400 microm wide passive conductor, with a distant but on-chip 400 microm wide pseudoreference electrode. Investigations involve solutions of potassium chloride electrolyte containing potassium ferrocyanide. Amplification factors were as high as 7.60, even with these microelectrodes of fairly large dimensions (which are generally less expensive, easier, and more reproducible to fabricate), because of the significant role that passive and active (instrumentally induced) redox cycling plays in confined volumes of enclosed microchannels. The studies are useful in optimizing designs for LOAC devices.
在微流控芯片(LOAC)设备中的微电极上进行电流检测,当体积小到扩散场在通量完全径向之前到达壁面时,其信号与背景比、减小的欧姆 iR 降和稳态信号优势就会丧失。电活性物质在多个紧密间隔的微电极之间进行氧化还原循环,可以克服这一限制,并提供放大能力。一种将微通道与可单独寻址的微带电极阵列集成在一起的器件,已经被用于研究在具有不同配置和数量的活性发生器和收集器的受限静态溶液中,由于氧化还原循环而导致的信号放大的影响。该微加工器件由一个 22 微米高、600 微米宽的微通道组成,其中包含一个由 50 微米宽、600 微米长的金微带组成的阵列,微带之间的间隙为 25 微米,交错排列着一个 800 微米宽的对电极和 400 微米宽的无源导体,以及一个距离较远但在芯片上的 400 微米宽的伪参比电极。研究涉及含有亚铁氰化钾的氯化钾电解质溶液。即使使用这些尺寸相当大的微电极(其通常更便宜、更容易且更易于重复制造),放大因子也高达 7.60,这是因为被动和主动(仪器诱导)氧化还原循环在封闭微通道的受限体积中起着重要作用。这些研究对于优化 LOAC 器件的设计很有用。