Objective-type dark-field illumination for scattering from microbeads

Ido Braslavsky, Roee Amit, B. M.Jaffar Ali, Opher Gileadi, Amos Oppenheim, Joel Stavans

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


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-tonoise 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.

Original languageAmerican English
Pages (from-to)5650-56579
Number of pages50930
JournalApplied Optics
Issue number31
StatePublished - 1 Nov 2001
Externally publishedYes


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