Martínez-López José I, Moncada-Hernández Héctor, Baylon-Cardiel Javier L, Martínez-Chapa Sergio O, Rito-Palomares Marco, Lapizco-Encinas Blanca H
Departamento de Biotecnología e Ingeniería de Alimentos y Centro de Biotecnología, Tecnológico de Monterrey, Campus Monterrey, Avenida Eugenio Garza Sada 2501 Sur, Monterrey, NL, 64849, México.
Anal Bioanal Chem. 2009 May;394(1):293-302. doi: 10.1007/s00216-009-2626-y. Epub 2009 Feb 4.
Insulator-based dielectrophoresis (iDEP), an efficient technique with great potential for miniaturization, has been successfully applied for the manipulation of a wide variety of bioparticles. When iDEP is applied employing direct current (DC) electric fields, other electrokinetic transport mechanisms are present: electrophoresis and electroosmotic flow. In order to concentrate particles, iDEP has to overcome electrokinetics. This study presents the characterization of electrokinetic flow under the operating conditions employed with iDEP; in order to identify the optimal conditions for particle concentration employing DC-iDEP, microparticle image velocimetry (microPIV) was employed to measure the velocity of 1-microm-diameter inert polystyrene particles suspended inside a microchannel made from glass. Experiments were carried out by varying the properties of the suspending medium (conductivity from 25 to 100 microS/cm and pH from 6 to 9) and the strength of the applied electric field (50-300 V/cm); the velocities values obtained ranged from 100 to 700 microm/s. These showed that higher conductivity and lower pH values for the suspending medium produced the lowest electrokinetic flow, improving iDEP concentration of particles, which decreases voltage requirements. These ideal conditions for iDEP trapping (pH = 6 and sigma(m) = 100 microS/cm) were tested experimentally and with the aid of mathematical modeling. The microPIV measurements allowed obtaining values for the electrokinetic mobilities of the particles and the zeta potential of the glass surface; these values were used with a mathematical model built with COMSOL Multiphysics software in order to predict the dielectrophoretic and electrokinetic forces exerted on the particles; the modeling results confirmed the microPIV findings. Experiments with iDEP were carried out employing the same microparticles and a glass microchannel that contained an array of cylindrical insulating structures. By applying DC electric fields across the insulating structures array, it was seen that the dielectrophoretic trapping was improved when the electrokinetic force was the lowest; as predicted by microPIV measurements and the mathematical model. The results of this study provide guidelines for the selection of optimal operating conditions for improving insulator-based dielectrophoretic separations and have the potential to be extended to bioparticle applications.
基于绝缘体的介电电泳（iDEP）是一种具有巨大小型化潜力的高效技术，已成功应用于多种生物粒子的操控。当采用直流（DC）电场应用iDEP时，还存在其他电动传输机制：电泳和电渗流。为了浓缩粒子，iDEP必须克服电动现象。本研究介绍了在iDEP使用的操作条件下电动流的特性；为了确定使用DC-iDEP进行粒子浓缩的最佳条件，采用了微粒图像测速技术（microPIV）来测量悬浮在由玻璃制成的微通道内的直径为1微米的惰性聚苯乙烯粒子的速度。通过改变悬浮介质的特性（电导率从25到100微西门子/厘米，pH值从6到9）和施加电场的强度（50 - 300伏/厘米）进行实验；获得的速度值范围为100到700微米/秒。这些结果表明，悬浮介质的较高电导率和较低pH值产生最低的电动流，改善了粒子的iDEP浓缩，这降低了电压要求。通过实验和借助数学建模测试了这些iDEP捕获的理想条件（pH = 6和σ(m)= 100微西门子/厘米）。microPIV测量允许获得粒子的电动迁移率值和玻璃表面的zeta电位；这些值与使用COMSOL Multiphysics软件构建的数学模型一起用于预测施加在粒子上的介电电泳力和电动力；建模结果证实了microPIV的发现。使用相同的微粒和包含圆柱形绝缘结构阵列的玻璃微通道进行了iDEP实验。通过在绝缘结构阵列上施加直流电场，可以看到当电动力最低时介电电泳捕获得到改善；正如microPIV测量和数学模型所预测的那样。本研究结果为选择最佳操作条件以改善基于绝缘体的介电电泳分离提供了指导方针，并且有可能扩展到生物粒子应用中。
