Ionic-surfactant-mediated electro-dewetting for digital microfluidics
Ionic-surfactant-mediated electro-dewetting for digital microfluidics
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DOI：
10.1038/s41586-019-1491-x
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发表时间：
2019-08-22
期刊：
影响因子：
64.8
通讯作者：
Kim, Chang-Jin 'CJ'
中科院分区：
文献类型：
--
作者：
Li, Jia;Ha, Noel S.;Kim, Chang-Jin 'CJ'
使用电信号（1）操纵基底上的液滴的能力（称为数字微流体）用于光学（2，3）、生物医学（4，5）、热（6）和电子（7）应用，并导致了商业上可用的液体透镜（8）和诊断试剂盒（9，10）。这种电致动主要通过电润湿来实现，其中液滴响应于所施加的电压而被吸引朝向导电基板并在导电基板上扩散。为了确保强而实用的致动，基板覆盖有电介质层和用于电介质上电润湿（EWOD）的疏水顶涂层（11-13）;这增加了致动电压（至约100伏），并且可能由于电介质击穿（14）、充电（15）和生物污垢（16）而损害可靠性。在这里，我们演示液滴操纵，使用电信号诱导液体去湿，而不是湿，亲水性导电基板，而不需要添加层。在这种电去湿机制中，其在现象学上与电润湿相反，液体-基底相互作用不直接由电场控制，而是由场诱导的离子表面活性剂与基底的附着和脱离控制。我们表明，这种驱动机制可以执行所有基本的数字微流体操作，使用水在掺杂的硅晶片在空气中，只有+/- 2.5伏的驱动电压，几微安的电流和约0.015倍的离子表面活性剂的临界胶束浓度。该系统还可以处理常见的缓冲液和有机溶剂，有望为广泛的应用提供简单可靠的微流体平台。
The ability to manipulate droplets on a substrate using electric signals(1)-known as digital microfluidics-is used in optical(2,3), biomedical(4,5), thermal(6) and electronic(7) applications and has led to commercially available liquid lenses(8) and diagnostics kits(9,10). Such electrical actuation is mainly achieved by electrowetting, with droplets attracted towards and spreading on a conductive substrate in response to an applied voltage. To ensure strong and practical actuation, the substrate is covered with a dielectric layer and a hydrophobic topcoat for electrowetting-on-dielectric (EWOD)(11-13); this increases the actuation voltage (to about 100 volts) and can compromise reliability owing to dielectric breakdown(14), electric charging(15) and biofouling(16). Here we demonstrate droplet manipulation that uses electrical signals to induce the liquid to dewet, rather than wet, a hydrophilic conductive substrate without the need for added layers. In this electrodewetting mechanism, which is phenomenologically opposite to electrowetting, the liquid-substrate interaction is not controlled directly by electric field but instead by field-induced attachment and detachment of ionic surfactants to the substrate. We show that this actuation mechanism can perform all the basic fluidic operations of digital microfluidics using water on doped silicon wafers in air, with only +/- 2.5 volts of driving voltage, a few microamperes of current and about 0.015 times the critical micelle concentration of an ionic surfactant. The system can also handle common buffers and organic solvents, promising a simple and reliable microfluidic platform for a broad range of applications.