Full text loading...
(Color) Schematic diagram of the experimental setup for implementing interactive optical manipulation of trapped particles. Components are not drawn to scale. A laser beam is coupled into a beam expander , which is then reflected off the micromirror array (DMD). All the mirrors in the micromirror array could be turned on, thereby acting as a large mirror, or the micromirror array could display a specific pattern to trap microspheres in a particular orientation (e.g., a checkerboard pattern). The beam reflected from the DMD is then coupled to an objective lens, which focuses the light into a spot onto the fiber bundle. Light is then transmitted through the fiber bundle and exits to form an array of optical traps. Therefore, the fiber bundle acts as a lens array. The microparticles flowing in solution are then trapped two dimensionally against the bottom of the sample chamber and are imaged with a CCD camera.
(Color online) Control of trapping regions by the DMD. A checkerboard pattern was created on the micromirror array and carried through the optical fiber. These images show the DMD patterns projected through the fiber bundle. Pixelation is due to the optical fiber bundle pattern. Trapping regions could be turned off or on by using the DMD software.
(Color online) Two experiments demonstrating DMD-based control of optical traps. Four individually addressable trapping regions were formed and used to capture or release microparticles. The first row of images in (a) and (b) shows the traps’ positions (on—light transmission through the fibers; off—no light transmission). The second row of images shows the trapped microspheres. The red circles indicate active trap locations, and beads outside of these regions are nontrapped particles. Once a trap is turned off, the trapped particle is released into the flowing solution. (a) and (b) show different sequences of trapping patterns created by the micromirror array. The position of the images is slightly shifted between the top and bottom lines. Also, note that each region can contain more than one bead because the trapping region is large relative to the bead size.
(Color online) Release and recapture of silica microspheres. (a) Four trapping regions, (i)–(iv), were formed, and microspheres were initially trapped in two regions, (i) and (iii). (b) The microspheres in region (i) were released, and due to the direction of the solution flow, they were recaptured in region (ii). (c) The two original trapping regions, (i) and (iv), were turned on again, and a new microparticle was trapped in the vacated trap (i). (d) All optical trapping regions were turned off, and all the microparticles were released.
Article metrics loading...