Objective-type dark-field illumination for scattering from microbeads.
We introduce a method for detecting and tracking small particles in a solution near a surface. The method is based on blocking the backreflected illumination beam in an objective-type total internal reflection microscope, leaving unhindered the light scattered by the particles and resulting in dark-field illumination. Using this method, we tracked the motion of 60-nm polystyrene beads with a signal-to-noise ratio of 6 and detected 20-nm gold particles with a signal-to-noise ratio of 5. We illustrate the method's use by following the Brownian motion of small beads attached by short DNA tethers to a substrate.
Braslavsky
I
I
Amit
R
R
Jaffar Ali
B M
BM
Gileadi
O
O
Oppenheim
A
A
Stavans
J
J