Chen Xiaoming, Ren Yukun, Hou Likai, Feng Xiangsong, Jiang Tianyi, Jiang Hongyuan
School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, PR China.
Analyst. 2019 Aug 16;144(17):5150-5163. doi: 10.1039/c9an01230c.
Five arc-shaped gaps were designed on the bipolar electrode to actuate alternately opposite-direction asymmetrical induced-charge electro-osmosis (AICEO) vortices, and we developed a microfluidic device using such asymmetrical vortices to realize particle separation. When the buoyancy force dominates in the vertical direction, particles stay at the channel bottom, experiencing a left deflection under the vortices in the convex arc areas. In contrast, when the levitation force induced by AICEO vortices overcomes the buoyancy force, particles are elevated to a high level and captured by right vortices, undergoing a right deflection under the vortices in the concave arc areas. Moreover, when particles pass through the concave or convex arc areas every time, their right or left deflections are enlarged gradually and the separation becomes more complete. Remarkably, as the light/small particles at low voltage, heavy/large particles can be elevated to a new high level and undergo right deflection by increasing the voltage. We first explicitly proved the separation principle and analyzed numerically its capability in density- and size-based separation. Depending on the study of the voltage-dependent AICEO characterization of 4 μm silica and 4 μm PMMA particles, we experimentally verified the feasibility of our device in density-based separation. According to the investigation of sensitivity to particle size, we separated multi-sized yeast cells to confirm the capability of our device in size-based separation. Finally, we extracted yeast cells from impeding particles, obtaining 96% purity. Additionally, we designed a 500 μm distance between the focusing and separation region to circumvent the problems caused by electric-field interaction. Our AICEO-based separation method holds potential to serve as a useful tool in transesterification of microalgal lipids to biodiesel and solar cell processing because of its outstanding advantages, such as gentle conditions, contact-free separation, high-sensitivity and high-efficiency separation capability.
在双极电极上设计了五个弧形间隙，以交替驱动相反方向的不对称感应电荷电渗（AICEO）涡旋，并且我们开发了一种利用这种不对称涡旋的微流控装置来实现颗粒分离。当浮力在垂直方向上占主导时，颗粒停留在通道底部，在凸弧区域的涡旋作用下向左偏转。相反，当AICEO涡旋产生的悬浮力克服浮力时，颗粒被提升到较高位置并被右涡旋捕获，在凹弧区域的涡旋作用下向右偏转。此外，当颗粒每次通过凹弧或凸弧区域时，它们的右偏或左偏会逐渐增大，分离变得更加完全。值得注意的是，对于低电压下的轻/小颗粒，通过增加电压，重/大颗粒可以被提升到新的较高位置并向右偏转。我们首先明确证明了分离原理，并对其基于密度和尺寸的分离能力进行了数值分析。根据对4μm二氧化硅和4μm聚甲基丙烯酸甲酯颗粒的电压依赖性AICEO特性的研究，我们通过实验验证了该装置在基于密度的分离中的可行性。根据对颗粒尺寸敏感性的研究，我们分离了多尺寸的酵母细胞，以确认该装置在基于尺寸的分离中的能力。最后，我们从阻碍颗粒中提取了酵母细胞，纯度达到96%。此外，我们在聚焦和分离区域之间设计了500μm的距离，以避免电场相互作用引起的问题。我们基于AICEO的分离方法因其温和的条件、无接触分离、高灵敏度和高效分离能力等突出优点，有望成为微藻脂质转化为生物柴油和太阳能电池加工中的有用工具。
