micro-oscillators are an emerging detection method that
has been shown to detect single bacteria in fluid – see
Figure. The technique is based on a magnetic microsphere’s
nonlinear rotational response to an external driving
magnetic field, i.e. the microsphere rotates out-of-synch
with the external magnetic field (see videos to the left).
Magnetic microspheres are latex spheres with incorporated
magnetic materials, such that they can be rotated in
magnetic fields. Their rotation rate can be easily
monitored with a low magnification microscope interfaced
to a CCD camera. Magnetic nonlinear micro-oscillators can
also be used to monitor single bacteria growth dynamics.
Nonlinear Rotation of Magnetic
R.R. Agayan, R. Clarke, R.
Kopelman, Single bacterial cell detection with nonlinear
rotation rate shifts of driven magnetic microspheres, Applied Physics
Letters, 91 (2007).
B.H. McNaughton and R. Kopelman,
Nonlinear rotation rate shifts of driven particles and uses
thereof, Patent Pending
R.R. Agayan, J.X. Wang, R. Kopelman,
Physiochemical microparticle sensors based on non-linear magnetic
oscillations, Sensors and Actuators B 121, 330-340 (2007).
Karen Kehbein, Jeffrey N. Anker and Raoul
udden breakdown in linear response of a
rotationally driven magnetic microparticle and application to physical and
J. Phys. Chem B. 110,18958 (2006).
with modulated optical nanoprobes (MOONs),” Journal
of Magnetism and Magnetic Materials 293, 663-670