Nanoscale Magnetic Materials - Magnetic Domains

Manipulation of magnetic microbeads

Magnetic surfaces for the controlled manipulation of superparamagnetic microbeads

Moving beadsThe manipulation of superparamagnetic microbeads with functionalized surfaces as labels for single-molecule studies, for cell manipulation, and detection of chemical or biological species in liquid environments are in the focus of the research project. Within the project the fundamentals for the movement of superparamagnetic beads on functionalized magnetic surfaces will be explored. As a basis for the manipulation of beads, micro-lithographically patterned magnetic surfaces in the form of array elements creating an interconnecting magnetic network will be investigated. The transport of individual beads is performed by micro-magnetic objects such as charged magnetic domain walls and switchable magnetization structures. 
Within the project the controlled movement of microbeads along magnetic structures with the help of variable multi-axis magnetic field protocols will be investigated. Different approaches are being explored for the transport of superparamagnetic particles in liquid suspensions. Moreover, hydrodynamic effects will be utilized by applying temporal and angle varying magnetic fields with different frequency components. The investigations will be supported by a combination of micro-magnetic and magnetic stray field simulations. The lateral distribution of the magnetic patterns and the corresponding motion of the microbeads are analyzed directly by complementary in-situ magnetic and bright-field optical microscopy. 

The research will open up new ways to laterally manipulate marked biological objects, to facilitate a controlled movement of particles in microfluidic environments over substantial distances, and in that way provide the foundations for the manipulation and separation of biological objects in integrated flowless lab-on-chip devices.

Magnetic surfaces at DFG Gepris.

  1. U. Sajjad, E. Lage, J. McCord, A trisymmetric magnetic microchip surface for free and two-way directional movement of magnetic microbeads, Advanced Materials Interfaces 5, 1801201 (2018) 
  2. U. Sajjad, R.B. Holländer, F. Klingbeil, J. McCord, Magnetomechanics of superparamagnetic beads on a magnetic Merry-Go-Round: from micromagnetics to radial looping, Journal of Physics D: Applied Physics 50, 135003 (2017)