Verlinden E J, Madadelahi M, Sarajlic E, Shamloo A, Engel A H, Staufer U, Ghatkesar M K
Department of Precision and Microsystems Engineering, Delft University of Technology, The Netherlands.
Nanoscale. 2020 May 14;12(18):10292-10305. doi: 10.1039/c9nr10494a.
We introduce a two-channel microfluidic atomic force microscopy (AFM) cantilever that combines the nanomechanical sensing functionality of an AFM cantilever with the ability to manipulate fluids of picolitres or smaller volumes through nanoscale apertures near the cantilever tip. Each channel is connected to a separate fluid reservoir, which can be independently controlled by pressure. Various systematic experiments with fluorescent liquids were done by either injecting the liquids from the on-chip reservoir or aspirating directly through the nanoscale apertures at the tip. A flow rate analysis of volume dosing, aspiration and concentration dosing inside the liquid medium was performed. To understand the fluid behaviour, an analytical model based on the hydrodynamic resistance, as well as numerical flow simulations of single and multi-phase conditions were performed and compared. By applying pressures between -500 mbar and 500 mbar to the reservoirs of the probe with respect to the ambient pressure, flow rates ranging from 10 fl s-1 to 83 pl s-1 were obtained inside the channels of the cantilever as predicted by the analytical model. The smallest dosing flow rate through the apertures was 720 fl s-1, which was obtained with a 10 mbar pressure on one reservoir and ambient pressure on the other. The solute concentration in the outflow could be tuned to values between 0% and 100% by pure convection and to values between 17.5% and 90% in combination with diffusion. The results prove that this new probe enables handling multiple fluids with the scope to inject different concentrations of analytes inside a single living cell and also perform regular AFM functionalities.
我们介绍了一种双通道微流控原子力显微镜（AFM）悬臂，它将AFM悬臂的纳米机械传感功能与通过悬臂尖端附近的纳米级孔操纵皮升或更小体积流体的能力相结合。每个通道都连接到一个单独的储液器，该储液器可通过压力独立控制。通过从片上储液器注入液体或直接通过尖端的纳米级孔抽吸，对荧光液体进行了各种系统实验。对液体介质内的体积定量给药、抽吸和浓度定量给药进行了流速分析。为了理解流体行为，基于流体动力阻力进行了分析模型，并对单相和多相条件下的数值流模拟进行了比较。通过相对于环境压力向探头的储液器施加-500毫巴至500毫巴之间的压力，如分析模型所预测的，在悬臂通道内获得了10飞秒每秒至83皮升每秒的流速。通过孔的最小定量给药流速为720飞秒每秒，这是在一个储液器上施加10毫巴压力而另一个储液器施加环境压力时获得的。流出物中的溶质浓度可通过纯对流调节至0%至100%之间的值，并结合扩散调节至17.5%至90%之间的值。结果证明，这种新型探头能够处理多种流体，有望在单个活细胞内注入不同浓度的分析物，并还能执行常规的AFM功能。
