Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Strasse 40, 34132, Kassel, Germany.
Artificial Intelligence Methods for Experiment Design (AIM-ED), Joint Lab of Helmholtzzentrum für Materialien und Energie, Berlin (HZB) and University of Kassel, Hahn-Meitner-Platz 1, 14109, Berlin, Germany.
Sci Rep. 2022 Dec 3;12(1):20890. doi: 10.1038/s41598-022-25391-z.
The transport of magnetic particles (MPs) by dynamic magnetic field landscapes (MFLs) using magnetically patterned substrates is promising for the development of Lab-on-a-chip (LOC) systems. The inherent close-to-substrate MP motion is sensitive to changing particle-substrate interactions. Thus, the detection of a modified particle-substrate separation distance caused by surface binding of an analyte is expected to be a promising probe in analytics and diagnostics. Here, we present an essential prerequisite for such an application, namely the label-free quantitative experimental determination of the three-dimensional trajectories of superparamagnetic particles (SPPs) transported by a dynamically changing MFL. The evaluation of defocused SPP images from optical bright-field microscopy revealed a "hopping"-like motion of the magnetic particles, previously predicted by theory, additionally allowing a quantification of maximum jump heights. As our findings pave the way towards precise determination of particle-substrate separations, they bear deep implications for future LOC detection schemes using only optical microscopy.
使用经过磁场图案化的基底通过动态磁场景观（MFL）来传输磁性颗粒（MPs），这对于开发片上实验室（LOC）系统很有前景。由于 MPs 靠近基底的固有运动对颗粒-基底相互作用的变化很敏感，因此，预计检测由于分析物的表面结合而导致的颗粒-基底分离距离的改变将成为分析和诊断中的一种很有前途的探针。在这里，我们提出了这种应用的一个基本前提，即使用动态变化的 MFL 来对超顺磁颗粒（SPP）的三维轨迹进行无标记的定量实验确定。对光学明场显微镜的离焦 SPP 图像的评估揭示了磁性颗粒的“跳跃”运动，这是之前的理论所预测的，此外还允许对最大跳跃高度进行定量。由于我们的发现为精确确定颗粒-基底分离铺平了道路，因此它们对于仅使用光学显微镜的未来 LOC 检测方案具有深远的意义。
