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Ionic-surfactant-mediated electro-dewetting for digital microfluidics
Nature ( IF 50.5 ) Pub Date : 2019-08-21 , DOI: 10.1038/s41586-019-1491-x
Jia Li 1 , Noel S Ha 2, 3 , Tingyi 'Leo' Liu 1, 4, 5 , R Michael van Dam 2, 3, 6, 7 , Chang-Jin 'cj' Kim 1, 2, 7
Nature ( IF 50.5 ) Pub Date : 2019-08-21 , DOI: 10.1038/s41586-019-1491-x
Jia Li 1 , Noel S Ha 2, 3 , Tingyi 'Leo' Liu 1, 4, 5 , R Michael van Dam 2, 3, 6, 7 , Chang-Jin 'cj' Kim 1, 2, 7
Affiliation
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The ability to manipulate droplets on a substrate using electric signals1—known as digital microfluidics—is used in optical2,3, biomedical4,5, thermal6 and electronic7 applications and has led to commercially available liquid lenses8 and diagnostics kits9,10. 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 breakdown14, electric charging15 and biofouling16. 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. A method of droplet manipulation is described that uses electrical signals to induce the liquid to dewet, rather than wet, a hydrophilic conductive surface.
中文翻译：
用于数字微流体的离子表面活性剂介导的电去湿
使用电信号 1（称为数字微流体）操纵基板上液滴的能力被用于光学 2、3、生物医学 4、5、热 6 和电子 7 应用，并导致商业上可用的液体透镜 8 和诊断套件 9、10。这种电驱动主要是通过电润湿来实现的，液滴响应于施加的电压被吸引到导电基板上并在其上扩散。为确保强大而实用的驱动，基板上覆盖有介电层和疏水性面漆，用于电介质上的电润湿 (EWOD)11-13；这会增加驱动电压（至约 100 伏），并且会因介电击穿 14、带电 15 和生物污垢 16 而影响可靠性。在这里，我们展示了使用电信号诱导液体去湿的液滴操作，而不是湿的，亲水的导电基板，无需添加层。在这种与电润湿现象相反的电极润湿机制中，液体-基材的相互作用不是由电场直接控制，而是由场诱导的离子表面活性剂对基材的附着和脱离控制。我们表明，这种驱动机制可以使用水在空气中的掺杂硅晶片上执行数字微流体的所有基本流体操作，只有 ±2.5 伏的驱动电压、几微安的电流和约 0.015 倍的离子临界胶束浓度。表面活性剂。该系统还可以处理常见的缓冲液和有机溶剂，为广泛的应用提供了一个简单可靠的微流体平台。
更新日期：2019-08-21
中文翻译：
用于数字微流体的离子表面活性剂介导的电去湿
使用电信号 1（称为数字微流体）操纵基板上液滴的能力被用于光学 2、3、生物医学 4、5、热 6 和电子 7 应用，并导致商业上可用的液体透镜 8 和诊断套件 9、10。这种电驱动主要是通过电润湿来实现的，液滴响应于施加的电压被吸引到导电基板上并在其上扩散。为确保强大而实用的驱动，基板上覆盖有介电层和疏水性面漆，用于电介质上的电润湿 (EWOD)11-13；这会增加驱动电压（至约 100 伏），并且会因介电击穿 14、带电 15 和生物污垢 16 而影响可靠性。在这里，我们展示了使用电信号诱导液体去湿的液滴操作，而不是湿的，亲水的导电基板，无需添加层。在这种与电润湿现象相反的电极润湿机制中，液体-基材的相互作用不是由电场直接控制，而是由场诱导的离子表面活性剂对基材的附着和脱离控制。我们表明，这种驱动机制可以使用水在空气中的掺杂硅晶片上执行数字微流体的所有基本流体操作，只有 ±2.5 伏的驱动电压、几微安的电流和约 0.015 倍的离子临界胶束浓度。表面活性剂。该系统还可以处理常见的缓冲液和有机溶剂，为广泛的应用提供了一个简单可靠的微流体平台。
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