University of Victoria, Electrical and Computer Engineering, Victoria, Canada.
Lab Chip. 2013 Oct 21;13(20):4142-6. doi: 10.1039/c3lc50772f. Epub 2013 Aug 23.
We use a double nanohole (DNH) optical trap to quantify the size and concentration of nanoparticles in solution. The time to trap shows a linear dependence with nanosphere size and a -2/3 power dependence with nanosphere concentration, which is in agreement with simple microfluidic considerations. The DNH approach has size-specificity on the order of a few nanometers, which was used to selectively quantify particles of a single size within a heterogeneous solution. By looking at individual trapping events, it is in principle possible to extend this approach to the ultimate limit of a single particle concentration, while also being able to operate at high concentrations in the same configuration. In addition, the DNH trap allows us to hold onto individual particles and thereby study constituents of a heterogeneous mixture. By repeating the trapping measurements on spherical particles of different refractive index, we found that the transmission step that indicates trapping scales empirically with the Clausius-Mossotti factor. This approach may be applied to several sensing applications, such as in the study of virus populations, where concentrations vary over many orders of magnitude.
我们使用双纳米孔（DNH）光阱来定量测定溶液中纳米颗粒的大小和浓度。捕获所需的时间与纳米球的大小呈线性关系，与纳米球的浓度呈-2/3 次幂关系，这与简单的微流控考虑相符。DNH 方法的尺寸特异性在几纳米的数量级，可用于选择性地定量测定异质溶液中单个尺寸的颗粒。通过观察单个捕获事件，原则上可以将该方法扩展到单个颗粒浓度的极限，同时也可以在相同配置下在高浓度下进行操作。此外，DNH 阱可以使我们抓住单个颗粒，从而研究异质混合物的组成部分。通过对不同折射率的球形颗粒重复进行捕获测量，我们发现表明捕获的透射步骤在经验上与克劳修斯-莫索蒂因子成比例。这种方法可应用于几种传感应用，例如在病毒种群的研究中，其中浓度在多个数量级上变化。
