3D micromanipulation and imaging of colloids has been achieved by combining optical tweezers and confocal microscopy using two microscope objectives. Arrays of up to several hundred time-shared traps have been created using acousto-optical deflectors. In addition, two axially separated trapping planes were addressed using a Pockels cell, making trapping and dynamic manipulation of 3D colloidal structures possible. Structures of high refractive index core-shell colloidal particles were trapped inside a concentrated dispersion of index-matched particles, thereby creating a nucleus for colloidal crystallization. Using confocal microscopy, the effects of such structures upon the non-trapped rest of the dispersion could be analysed quantitatively in 3D.

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Journal Microsc. Anal.: UK edition
van der Horst, A, Vossen, D.L.J, Visscher, K, Dogterom, M, & van Blaaderen, A. (2005). Manipulation and imaging of particles with optical tweezers and confocal microscopy. Microsc. Anal.: UK edition, 15–17.