Integrated capture, transport, and magneto-mechanical resonant sensing of superparamagnetic microbeads using magnetic domain walls

Abstract

An integrated platform for the capture, transport, and detection of individual superparamagnetic microbeads is described for lab-on-a-chip biomedical applications. Magnetic domain walls in magnetic tracks have previously been shown to be capable of capturing and transporting individual beads through a fluid at high speeds. Here it is shown that the strong magnetostatic interaction between a bead and a domain wall leads to a distinct magneto-mechanical resonance that reflects the susceptibility and hydrodynamic size of the trapped bead. Numerical and analytical modeling is used to quantitatively explain this resonance, and the magneto-mechanical resonant response under sinusoidal drive is experimentally characterized both optically and electrically. The observed bead resonance presents a new mechanism for microbead sensing and metrology. The dual functionality of domain walls as both bead carriers and sensors is a promising platform for the development of labon-a-bead technologies.

Transport dynamics of superparamagnetic microbeads trapped by mobile magnetic domain walls

“…In conjunction with the capability for resonant detection of individual beads 26,30 , the bead-DW system has exciting and promising application in future lab-on-a-chip technologies. …”

“…In earlier work 25,26 , we demonstrated that this curved geometry can be extended into a curvilinear backbone to design long-distance linear transport conduits driven by a rotating magnetic field. The knocking transport mode, however, also has implications for moving beads along simpler geometries such as straightaways, where DWs travel much faster than .…”

“…Once the bead is trapped in the potential well of the DW, the DW can be used to manipulate individual beads. Indeed, bead transport has been realized by either stepping a bead from one DW trap site to the next 19,[21][22][23][24]27 or moving it continuously with a propagating DW 20,22,25,26 . Continuous transport is limited, however, by the maximum interaction force, or binding force , between the bead and DW, which must overcome the hydrodynamic drag force on the bead as it is pulled through the host fluid 20 .…”

Angular-dependent magnetization reversal processes in artificial spin ice

“…Localised magnetic charges can be supported at the interconnections and the ability to manipulate magnetic charges in the form of magnetic domain walls (DWs) provides the basis for novel technological devices including information processing 1 and through the manipulation of bio-or chemically-functionalised magnetic nanoparticles. [2][3][4][5][6] Additionally, the patterning of 'artificial spin ice' geometries can give rise to a large number of energetically equivalent states which has been explored in both dipolar coupled systems 7,8 and interconnected networks. 9 Such structures have been suggested for macroscopic studies of fundamental frustrated phenomena and their associated emergent behavior showing strong links to the thermodynamics of the system.…”

Isolation of cells for selective treatment and analysis using a magnetic microfluidic chip

“…Darabi et al employed an array of thin nickel stripes on a glass substrate excited by an array of external magnets to separate CD4 þ T cells from peripheral blood with 90% purity. 12 The magnetic elements can be either passive or active; passive elements are usually softferromagnetic structures, [13][14][15][16][17][18] while active elements are microelectromagnets. [19][20][21][22][23][24][25] Soft-ferromagnetic structures can be magnetized by applying an external magnetic field and demagnetized by removing the field.…”