Gu Zhen, Luo Jing-Jing, Ding Le-Wei, Yan Bing-Yong, Zhou Jia-Le, Wang Jun-Gang, Wang Hui-Feng, Kong Cong
Key Laboratory of Advanced Control and Optimization for Chemical Processes Ministry of Education, East China University of Science and Technology, Shanghai 200237, China.
School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418, China.
Micromachines (Basel). 2021 Nov 19;12(11):1423. doi: 10.3390/mi12111423.
Digital microfluidic (DMF) has been a unique tool for manipulating micro-droplets with high flexibility and accuracy. To extend the application of DMF for automatic and in-site detection, it is promising to introduce colorimetric sensing based on gold nanoparticles (AuNPs), which have advantages including high sensitivity, label-free, biocompatibility, and easy surface modification. However, there is still a lack of studies for investigating the movement and stability of AuNPs for in-site detection on the electrowetting-based digital microfluidics. Herein, to demonstrate the ability of DMF for colorimetric sensing with AuNPs, we investigated the electrowetting property of the AuNPs droplets on the hydrophobic interface of the DMF chip and examined the stability of the AuNPs on DMF as well as the influence of evaporation to the colorimetric sensing. As a result, we found that the electrowetting of AuNPs fits to a modified Young-Lippmann equation, which suggests that a higher voltage is required to actuate AuNPs droplets compared with actuating water droplets. Moreover, the stability of AuNPs was maintained during the processing of electrowetting. We also proved that the evaporation of droplets has a limited influence on the detections that last several minutes. Finally, a model experiment for the detection of Hg was carried out with similar results to the detections in bulk solution. The proposed method can be further extended to a wide range of AuNPs-based detection for label-free, automatic, and low-cost detection of small molecules, biomarkers, and metal ions.
数字微流控（DMF）一直是一种用于以高灵活性和高精度操纵微滴的独特工具。为了扩展DMF在自动现场检测中的应用，引入基于金纳米颗粒（AuNPs）的比色传感很有前景，金纳米颗粒具有高灵敏度、无标记、生物相容性好以及易于表面修饰等优点。然而，对于基于电润湿的数字微流控上用于现场检测的AuNPs的运动和稳定性的研究仍然缺乏。在此，为了证明DMF用于AuNPs比色传感的能力，我们研究了AuNPs液滴在DMF芯片疏水界面上的电润湿特性，考察了AuNPs在DMF上的稳定性以及蒸发对比色传感的影响。结果，我们发现AuNPs的电润湿符合修正的杨氏-利普曼方程，这表明与驱动水滴相比，驱动AuNPs液滴需要更高的电压。此外，在电润湿过程中AuNPs的稳定性得以保持。我们还证明了液滴蒸发对持续几分钟的检测影响有限。最后，进行了汞检测的模型实验，结果与在本体溶液中的检测结果相似。所提出的方法可以进一步扩展到广泛的基于AuNPs的检测，用于小分子、生物标志物和金属离子的无标记、自动和低成本检测。
