Self-Regulated, Droplet-Based Sample Chopper for Microfluidic Absorbance Detection
Self-Regulated, Droplet-Based Sample Chopper for Microfluidic Absorbance Detection
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DOI：
10.1021/ac202791d
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发表时间：
2012-02-07
影响因子：
7.4
通讯作者：
Easley, Christopher J.
中科院分区：
文献类型：
--
作者：
Deal, Kennon S.;Easley, Christopher J.
类似于光束斩波，我们证明了油中水滴的形成和路径可以斩波流体样品以允许相敏检测。这种手动微流控样品斩波器（μ Chopper）大大降低了27μm光路中分子吸光度的检测限。由于吸光度直接依赖于光程长度，因此与微流体根本不兼容。虽然其他微流体吸光度方法在制造中使用复杂的附加装置，例如光纤耦合和增加的光路，但这种自调节 mu 斩波器使用相反的液滴发生器来被动地交替样品和参考液滴，每个液滴的频率大约为 10 Hz。每个液滴的身份都会自动锁定到其发生器，从而允许下游锁定分析几乎消除大信号漂移或 1/f 噪声。锁定时间常数为 1.9 s，总询问体积为 59 nL（122 个液滴），仅使用光学显微镜和标准单深度 (27 μ m) 微流体装置即可实现 3.0 x 10(-4) 吸光度单位或 500 nM 溴酚蓝 (BPB) (29 fmol) 的检测限。该系统进一步应用于纳升 pH 传感，并用分光光度计进行验证。 mu Chopper 代表光束斩波器的流体模拟，并且自我调节的样品/参考液滴交替提高了易用性。
Akin to optical beam chopping, we demonstrate that formation and routing of aqueous droplets in oil can chop a fluidic sample to permit phase sensitive detection. This hand-operated microfluidic sample chopper (mu Chopper) greatly reduces the detection limit of molecular absorbance in a 27 mu m optical path. With direct dependence on path length, absorbance is fundamentally incompatible with microfluidics. While other microfluidic absorbance approaches use complex additions to fabrication, such as fiber coupling and increased optical paths, this self-regulated mu Chopper uses opposing droplet generators to passively alternate sample and reference droplets at similar to 10 Hz each. Each droplet's identity is automatically locked-in to its generator, allowing downstream lock-in analysis to nearly eliminate large signal drift or 1/f noise. With a lock-in time constant of 1.9 s and total interrogated volume of 59 nL (122 droplets), a detection limit of 3.0 x 10(-4) absorbance units or 500 nM bromophenol blue (BPB) (29 fmol) was achieved using only an optical microscope and a standard, single-depth (27 mu m) microfluidic device. The system was further applied to nanoliter pH sensing and validated with a spectrophotometer. The mu Chopper represents a fluidic analog to an optical beam chopper, and the self-regulated sample/reference droplet alternation promotes ease of use.