15 Smart Platforms for Biomedical Applications
361
Permalloy
Au
Au
…
…
Au
Au
Pt
CoFeB
Ru
Fig. 15.4 Schematic of two types of microdiscs. The permalloy vortex microdisc (left) has a
flux closure magnetization state to ensure a net zero remanent state. The out-of-plane magnetized
microdisc (right) utilizes a heterostructure of CoFeB/Pt (for example) to achieve a magnetization perpendicular to the plane of the disc. The Ru interlayer creates an AP remanent state. Both
microdiscs are capped with Au for biofunctionalization. The blue arrows denote the magnetization
vectors of the magnetic layers in expanded views
AF coupling causes the thin film to have a net zero magnetization at remanence. AF
RKKY coupling has been used to create microdiscs with the remanent AP configuration in in-plane magnetic layers (both with and without the vortex configuration)
[118, 119], as well as in microdiscs based on perpendicularly magnetized [120–123]
magnetic layers [101, 124, 125] (Fig. 15.4).
15.2.1 Applications
15.2.1.1 Mechanical Actuation
Solution suspended lithographically defined microdiscs have been used almost solely
for the mechanical destruction of cancer cells, the original application for which they
were conceived [36]. The high anisotropy of magnetic thin films translates to the
generation of extremely high magnetic torques that are effectively transduced by the
planar microdiscs themselves.
Initial work in this space used 2 μm vortex microdiscs in an oscillating magnetic
field to destroy glioblastoma cells in vitro [36]. More recently, there has also been
interest in using microdiscs fabricated from perpendicularly magnetized thin films
for mechanical actuation [101, 124–127]. The mechanical actuation of micro- and
nanodiscs structures has been shown to cause significant cell death both in vitro [36,
125] and in vivo [127] and has also been demonstrated in drug delivery-type systems
where the actuation can trigger release of a therapeutic [126, 128, 129]. Recent work
has been focussed on elucidating the most efficient systems for torque transduction
from an applied field, and how that affects the therapeutic efficacy of the particles in
a biological system [125].
361
Permalloy
Au
Au
…
…
Au
Au
Pt
CoFeB
Ru
Fig. 15.4 Schematic of two types of microdiscs. The permalloy vortex microdisc (left) has a
flux closure magnetization state to ensure a net zero remanent state. The out-of-plane magnetized
microdisc (right) utilizes a heterostructure of CoFeB/Pt (for example) to achieve a magnetization perpendicular to the plane of the disc. The Ru interlayer creates an AP remanent state. Both
microdiscs are capped with Au for biofunctionalization. The blue arrows denote the magnetization
vectors of the magnetic layers in expanded views
AF coupling causes the thin film to have a net zero magnetization at remanence. AF
RKKY coupling has been used to create microdiscs with the remanent AP configuration in in-plane magnetic layers (both with and without the vortex configuration)
[118, 119], as well as in microdiscs based on perpendicularly magnetized [120–123]
magnetic layers [101, 124, 125] (Fig. 15.4).
15.2.1 Applications
15.2.1.1 Mechanical Actuation
Solution suspended lithographically defined microdiscs have been used almost solely
for the mechanical destruction of cancer cells, the original application for which they
were conceived [36]. The high anisotropy of magnetic thin films translates to the
generation of extremely high magnetic torques that are effectively transduced by the
planar microdiscs themselves.
Initial work in this space used 2 μm vortex microdiscs in an oscillating magnetic
field to destroy glioblastoma cells in vitro [36]. More recently, there has also been
interest in using microdiscs fabricated from perpendicularly magnetized thin films
for mechanical actuation [101, 124–127]. The mechanical actuation of micro- and
nanodiscs structures has been shown to cause significant cell death both in vitro [36,
125] and in vivo [127] and has also been demonstrated in drug delivery-type systems
where the actuation can trigger release of a therapeutic [126, 128, 129]. Recent work
has been focussed on elucidating the most efficient systems for torque transduction
from an applied field, and how that affects the therapeutic efficacy of the particles in
a biological system [125].