Abstract
A technology platform based on a remotely controlled and stepwise transport of an array arrangement of superparamagnetic beads (SPB) for efficient molecular uptake, delivery and accumulation in the context of highly specific and sensitive analyte molecule detection for the application in lab-on-a-chip devices is presented. The near-surface transport of SPBs is realized via the dynamic transformation of the SPBs’ magnetic potential energy landscape above a magnetically stripe patterned Exchange-Bias (EB) thin film layer systems due to the application of sub-mT external magnetic field pulses. In this concept, the SPB velocity is dramatically influenced by the magnitude and gradient of the magnetic field landscape (MFL) above the magnetically stripe patterned EB substrate, the SPB to substrate distance, the magnetic properties of both the SPBs and the EB layer system, respectively, as well as by the properties of the external magnetic field pulses and the surrounding fluid. The focus of this review is laid on the specific MFL design in EB layer systems via light-ion bombardment induced magnetic patterning (IBMP). A numerical approach is introduced for the theoretical description of the MFL in comparison to experimental characterization via scanning Hall probe microscopy. The SPB transport mechanism will be outlined in terms of the dynamic interplay between the EB substrate’s MFL and the pulse scheme of the external magnetic field.
Highlights
The advent of micro-total-analysis-systems and lab-on-a-chip (LOC) devices will enable the transfer of conventionalchemical analysis techniques, usually carried out by expensive and bulky laboratory equipment, to handheld and comparably inexpensive devices on centimeter length scales [1,2,3,4,5,6,7,8]
The present report described fundamentals and technology for a superparamagnetic beads (SPB) transport based technology platform to be used for LOC or μTAS devices in biotechnology
This platform has a large potential for applications in biosensors as different tasks can be carried out by the SPBs on-chip
Summary
The advent of micro-total-analysis-systems (μTAS) and lab-on-a-chip (LOC) devices will enable the transfer of conventional (bio)chemical analysis techniques, usually carried out by expensive and bulky laboratory equipment, to handheld and comparably inexpensive devices on centimeter length scales [1,2,3,4,5,6,7,8]. Since the detection volume is usually smaller in comparison to the liquid volume of the whole μTAS or LOC device, the naturally occurring number of analyte molecules within the detection volume may not be sufficient in order to generate a significant measuring signal In this case, an efficient and specific transport of analyte molecules from the available liquid into the investigated detection volume is necessary [27]. For efficient analyte detection an analyte-specific and sensitive quantitative detection technology must be available In principle such devices can be realized using a combination of a fluid flow in microfluidic channels together with capture molecule-functionalized surfaces or superparamagnetic beads for the transport of biomolecules or cells [28,29,30,31], several technical and practical challenges have to be met, covering both the type of beads and the transport concept to be used as well as the class of capture molecules. The magnetic force FM acting on a SPB (hydrodynamic volume VSPB , volume averaged susceptibility SPB ) in a fluid (volume averaged susceptibility L ) induced by a magnetic gradient field B can be written as [33,34]:
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