Matthew McMahon, Andrew Berglund, Peter Carmichael, Jabez McClelland, J. Alexander Liddle


            Constructing 2D lateral particle trajectories from digital video sequences of nanoparticle motion in a liquid is straightforward and fairly common, requiring only the use of centroid-finding algorithms. On the other hand, extracting particle trajectories in the third (out-of-plane) dimension has been more difficult, requiring detailed calibration of the radius of the defocused diffracted rings which result from vertical fluctuations of particle position.  We introduce a new technique, termed orthogonal tracking microscopy or orthogonal projection microscopy, in which integrated micromirrors produce one or more reflected images of a particle within the same field of view as the direct image.  The reflected images project vertical motion into lateral motion.   Thus, we are able to construct a fully 3D particle trajectory from 2D digital video using only centroid-finding algorithms.  We use this technique to study particle-surface interactions relevant to directed assembly of nanoparticles. 


Name: Matthew McMahon

Mentor: J. Alexander Liddle

Div: 620


Bldg. 216/A149

Mailstop 6203

Phone: 301-975-2325

Fax: 301-926-2746

Email: matthew.mcmahon@nist.gov

(Neither I nor my mentor are Sigma Xi members)

Category: Physics