Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
Nat Commun. 2022 Apr 6;13(1):1869. doi: 10.1038/s41467-022-29405-2.
Open-channel microfluidics enables precise positioning and confinement of liquid volume to interface with tightly integrated optics, sensors, and circuit elements. Active actuation via electric fields can offer a reduced footprint compared to passive microfluidic ensembles and removes the burden of intricate mechanical assembly of enclosed systems. Typical systems actuate via manipulating surface wettability (i.e., electrowetting), which can render low-voltage but forfeits open-microchannel confinement. The dielectric polarization force is an alternative which can generate open liquid microchannels (sub-100 µm) but requires large operating voltages (50-200 V) and low conductivity solutions. Here we show actuation of microchannels as narrow as 1 µm using voltages as low as 0.5 V for both deionized water and physiological buffer. This was achieved using resonant, nanoscale focusing of radio frequency power and an electrode geometry designed to abate surface tension. We demonstrate practical fluidic applications including open mixing, lateral-flow protein labeling, filtration, and viral transport for infrared biosensing-known to suffer strong absorption losses from enclosed channel material and water. This tube-free system is coupled with resonant wireless power transfer to remove all obstructing hardware - ideal for high-numerical-aperture microscopy. Wireless, smartphone-driven fluidics is presented to fully showcase the practical application of this technology.
开式微流控技术可实现对液体体积的精确定位和限制，使其与紧密集成的光学、传感器和电路元件相连接。与被动微流控组件相比，通过电场进行主动致动可以减小设备尺寸，并省去封闭系统中复杂机械组件的装配工作。典型的系统通过操控表面润湿性（即电润湿）来进行致动，这虽然可以实现低电压操作，但会丧失开放式微通道的限制。介电泳力是另一种替代方法，它可以产生开放式液体微通道（小于 100 µm），但需要大的工作电压（50-200 V）和低电导率溶液。在这里，我们展示了使用低至 0.5 V 的电压，对窄至 1 µm 的微通道进行致动，无论是去离子水还是生理缓冲液都可以实现这一点。这是通过共振、纳秒级聚焦射频功率以及旨在消除表面张力的电极几何形状来实现的。我们展示了实际的流体应用，包括开放式混合、侧向流蛋白质标记、过滤和病毒运输，这些应用对于红外生物传感非常重要，因为封闭通道材料和水会导致强烈的吸收损失。该无管系统与共振无线功率传输相结合，可以去除所有阻碍硬件，非常适合高数值孔径显微镜。我们还展示了无线、智能手机驱动的流体学，以充分展示这项技术的实际应用。
