4D
defocused particle tracking (DPT) technique
As we enter the era of
quantitative biology, there is an immediate need for a new set of
quantitative tools to probe the spatial and dynamical information of
biological entities (such as bacterial cells, proteins) at micro
and nano scales. We have developed imaging
techniques that are able to track micron meter scale particles in
all four
dimensions (x,y,z,t) using a
single CCD video camera.
The
idea behind this imaging technology is straightforward. When a point
like object is in focus, one gets a focused point in the imaging plane;
when a point like object moves away from the focal plane, one gets a
fuzzy dot in the imaging plane. The graph below shows images of a 1
micron fluorescent bead at different vertical positions using an
epi-fluorescent microscope. As seen the defocused image contains all
the information necessary to infer the (x,y,z) location of the
fluorescent beads.
Fig. 1 Defocoused
images of
a 1um diameter fluorescent bead at different z locations.
Here are a few successful
examples using the 4D DPT technology
Tracking
swimming E.coli in four dimensions.
Revealing Lagrangian flow fields in a micro
mixer.
If you are interested in using our automatic tracker, please contact
Mingming Wu at mw272@cornell.edu. You can also
download the tracking software at 4D-Tracker.
This is a series of program that (1) translates images with defocused
particle images into (x,y,z,t) coordinates; (2) forming trajectories by
connecting particles of nearest neighbors.
Publications:
- Mingming
Wu, John Roberts, and Mark Buckley, Three-dimensional
fluorescent particle tracking at micron-scale using a
single camera, Experiments in Fluids, 38, 461-465(2005).
- Mingming
Wu and Morteza Gharib, Experimental
studies on the shape and path of small air bubbles rising in clean water,
Physics of Fluids, 14,
L49(2002)