Fabrication of carbon microelectrodes with a micromolding technique and their use in microchip-based flow analyses
Fabrication of carbon microelectrodes with a micromolding technique and their use in microchip-based flow analyses
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DOI：
10.1039/b401380h
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发表时间：
2004-01-01
期刊：
影响因子：
4.2
通讯作者：
Martin, RS
中科院分区：
文献类型：
--
作者：
Kovarik, ML;Torrence, NJ;Martin, RS
在本文中，我们报告了一种用于微流体的碳微电极图案化新技术。这种技术被称为碳墨水微成型，使用聚（二甲基硅氧烷）（PDMS）微通道来限定微电极的尺寸。首先，通过软光刻技术制作微电极所需尺寸的 PDMS 微通道。然后将 PDMS 可逆地密封到基底上，并用碳墨水填充微通道。经过加热步骤后，PDMS 模具被移除，留下尺寸略小于原始 PDMS 微通道的碳微电极。由此产生的微电极（27微米宽，6微米高）可以可逆地密封到基于PDMS的流道上。荧光显微镜显示，即使流速达到 10 μL min(-1)，芯片/电极密封周围也没有发生泄漏。通过基于微芯片的流动注射分析对电极进行了表征。在 Hank 平衡盐溶液 (pH 7.4) 中注射儿茶酚，显示从 2 mM 到 10 muM (r(2) = 0.995) 的线性响应，灵敏度为 56.5 pA muM(-1)，估计检测限为 2 muM（0.27 皮摩尔，S/N = 3）。通过重复注射 (n = 10) 500 muM 儿茶酚溶液显示电极响应的重现性，RSD 为 4.6%。最后，通过用全氟阳离子交换聚合物 Nafion 涂覆微电极来证明选择性。多巴胺在改进的微电极上表现出响应，而抗坏血酸则被 Nafion 涂层排斥。这些电极为微流体应用提供了廉价的检测器，同时也是使用其他碳微电极材料（例如碳纤维）的可行替代品。此外，无法使用最先进的微加工设施的研究人员会对微电极的生产方式感兴趣。
In this paper, we report a new technique to pattern carbon microelectrodes for use in microfluidics. This technique, termed micromolding of carbon inks, uses poly(dimethylsiloxane) (PDMS) microchannels to define the size of the microelectrode. First, PDMS microchannels of the approximate dimensions desired for the microelectrode are made by soft lithography. The PDMS is then reversibly sealed to a substrate and the microchannels are filled with carbon ink. After a heating step the PDMS mold is removed, leaving a carbon microelectrode with a size slightly smaller than the original PDMS microchannel. The resulting microelectrode (27 mum wide and 6 mum in height) can be reversibly sealed to a PDMS-based flow channel. Fluorescence microscopy showed that no leakage occurred around the chip/electrode seal, even up to flow rates of 10 muL min(-1). The electrode was characterized by microchip-based flow injection analysis. Injections of catechol in Hank's Balanced Salt Solution (pH 7.4), showed a linear response from 2 mM to 10 muM (r(2) = 0.995), with a sensitivity of 56.5 pA muM(-1) and an estimated limit of detection of 2 muM (0.27 picomole, S/N = 3). Reproducibility of the electrode response was shown by repeated injections (n = 10) of a 500 muM catechol solution, resulting in a RSD of 4.6%. Finally, selectivity was demonstrated by coating the microelectrode with Nafion, a perfluoronated cation exchange polymer. Dopamine exhibited a response at the modified microelectrode while ascorbic acid was rejected by the Nafion-coating. These electrodes provide inexpensive detectors for microfluidic applications while also being viable alternatives to use of other carbon microelectrode materials, such as carbon fibers. Furthermore, the manner in which the microelectrodes are produced will be of interest to researchers who do not have access to state of the art microfabrication facilities.