AC electrothermal enhancement of heterogeneous assays in microfluidics
AC electrothermal enhancement of heterogeneous assays in microfluidics
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DOI：
10.1039/b706745c
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发表时间：
2007-01-01
期刊：
影响因子：
6.1
通讯作者：
Meinhart, Carl D.
中科院分区：
文献类型：
--
作者：
Feldman, Hope C.;Sigurdson, Marin;Meinhart, Carl D.
交流驱动的微流控技术可以将微流控系统中异质免疫传感器的时间性能提高近一个数量级。AC电动力用于产生湍流，这反过来又产生循环搅拌流体运动，增强扩散限制蛋白质的运输。这在悬浮抗原和壁固定化抗体之间提供了更多的结合机会。我们使用生物素-链霉亲和素非均相测定法，在该测定法中，生物素被固定化，并且荧光标记的链霉亲和素悬浮在高电导率缓冲液（σ = 1.0 S m（-1））中，通过实验研究了连续搅拌的有效性。将微加工电极集成在微孔内，并以f = 200 kHz和10 V-rms的频率驱动。荧光强度测量表明，对于5分钟的测定，连续搅拌使结合速率增加了几乎9倍。在长达15分钟的较长测定中测量到类似的结合改善。该测定的荧光增强被数值模拟，并与实验结合率一致。测得的流体速度为22 +/- 2 μ m/s（-1），明显低于数值模型预测的1.1 mm/s（-1），但仍显示出与施加电势相同的四次方依赖性。结果表明，对于微流体扩散限制传感器，连续搅拌能够在给定的时间限制内可靠地提高响应时间和灵敏度。
AC- driven electrothermal flow is used to enhance the temporal performance of heterogeneous immuno- sensors in microfluidic systems by nearly an order of magnitude. AC electrokinetic forces are used to generate electrothermal flow, which in turn produces a circular stirring fluid motion that enhances the transport of diffusion-limited proteins. This provides more binding opportunities between suspended antigens and wall- immobilized antibodies. We investigate experimentally the effectiveness of electrothermal stirring, using a biotin - streptavidin heterogeneous assay, in which biotin is immobilized, and fluorescently-labeled streptavidin is suspended in a high conductivity buffer (sigma = 1.0 S m(-1)). Microfabricated electrodes were integrated within a microwell and driven at a frequency of f = 200 kHz and 10 V-rms. Fluorescent intensity measurements show that for a five minute assay, electrothermal stirring increases the binding rate by a factor of almost nine. Similar binding improvement was measured for longer assays, up to fifteen minutes. The electrothermal enhancement of this assay was modeled numerically and agrees with experimental binding rates. The measured fluid velocity of 22 +/- 2 mu m s(-1) was significantly lower than that predicted by the numerical model, 1.1 mm s(-1), but nevertheless shows the same fourth power dependence on applied potential. The results demonstrate the ability for electrothermal stirring to reliably improve the response time and sensitivity within a given time limit for microfluidic diffusion-limited sensors.