Three-dimensional close-to-substrate trajectories of magnetic microparticles in dynamically modified magnetic field landscapes
The three-dimensional movement of superparamagnetic particles above a magnetically structured substrate in aqueous fluid was quantitatively determined using a standard light microscope with high temporal resolution. This allows for a better understanding of particle transport dynamics for targeted applications in future lab-on-a-chip systems.
To realize so-called lab-on-a-chip systems, which are intended to provide a fast and cost-effective detection method for, for example, pathogens, the use of magnetic particles in the nano-/micrometer size range is considered promising. Typically, the particles are guided deliberately over a topographically flat substrate surface, resulting in the interactions between particles and the underlying substrate playing a significant role in the behaviour of the particles. Additionally, it is expected that when an analyte (e.g., disease marker) binds to the particle or substrate surface, a modified particle-substrate distance arises due to the altered interactions, which can than be utilized for analyte detection.
In order to gain a fundamental understanding of both magnetic and electrostatic particle-substrate interactions, this study investigated the three-dimensional movement behavior of directionally transported superparamagnetic particles above a flat substrate in an aqueous environment.
The substrate in this case contained a prototype magnetic stripe domain pattern with alternating magnetizations of the stripes. This results in a customized magnetic scattered field landscape above the substrate, which, in combination with external magnetic field pulses, leads to the initiation of a stepwise transport of the particles. Through a corresponding calibration procedure for the vertical z-position of the particles, the theoretically expected jump during a transport step was demonstrated. Additionally, maximum jump heights of the particles were quantified and compared with a theoretical model for the dynamically varying particle-substrate distance. Future experiments will now apply the developed three-dimensional tracking method to measure absolute particle-substrate distances.
R. Huhnstock et al.,
Scientific Reports 12 20890 (2022)
DOI: 10.1038/s41598-022-25391-z
Dr. Rico Huhnstock
AGE – Funktionale dünne Schichten