BACKGROUND:  Understanding how to manipulate complex colloidal shapes optically is opening up new possibilities for controlling the construction of microscale assemblies. Optical traps, known as "laser tweezers," represent a simple method for potentially manipulating moveable microscopic particles. A variety of microscale dielectric objects, such as spheres, cubes, rods, disks, and crosses have been trapped and manipulated using laser tweezers, yet the general rules for determining whether a particle having a complex shape can be optically trapped and, if so, what its position and orientation would be, are not well understood. The simultaneous translational and orientational control of two or more complex-shaped particles brought into proximity and bonded together in a user-selected configuration has not been previously achieved.

INNOVATION:  Researchers at UCLA have shown that particles can be trapped in multiple different points using laser tweezers. Through exploiting the diversity of microscopic particles, and systematically varying particles' shapes, the researchers have discovered a range of interesting trapping phenomena that can arise when laser tweezers are applied to complex dielectric structures. Commercial applications include building microscale biparticle or multiparticle devices having complex shapes and compositions useful in advanced pharmaceutical drug delivery, micro-architectural engineering, and in advanced security approaches.

POTENTIAL APPLICATIONS 

• Enables optically directed assembly of complex-shaped three-dimensional particles to form devices comprised of two or more micro- or nano-scopic particles
• Provides a means of precisely building microscale devices and architectures using optical fields to attach and connect microscale parts together

ADVANTAGES

• Building highly controlled microscopic three-dimensional assemblies from two or more complex particles in a precise manner
• Can be combined with complex optical fields in parallel to facilitate precise orientation of the particles and high-throughput assembly production

DEVELOPMENT-TO-DATE:  Optical trapping and manipulation of letter shapes has been demonstrated to spell words. Assemblies of two or more complex-shaped particles using optical manipulation have been achieved using position-controlled dual laser tweezers.

Related Papers (Selected)

• Multiple trapped states and angular Kramers hopping of complex dielectric shapes in a simple optical trap, J.N. Wilking and T.G. Mason, Europhys. Lett. 81 58005/p1-p5 (2008). [more]

Reference: UCLA Case No. 2008-091