Colloidal Particle Geometry and Its Effect on Optical Trapping

ORAL

Abstract

Recent experiments by Wilking and Mason (Europhysics Letters, in press) on the laser trapping of colloids of various shapes (the letters of the alphabet) show that for identical chemistries the trapping force varies wildly with particle shape. In fact, certain shapes do not trap at all. Motivated by these experimental results, we explore the trapping of particle of variable shape using a ray-optics simulation. This numerical tool allows us to perform Monte Carlo integrations of the total trapping forces and torques for a series of objects such as a cross (the letter ``x'') or a beam (the letter ``I''). We find that certain shapes feature bi-stable trapping positions/orientations, and some, indeed, do not allow for trapping at all.

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Authors

  • Rachael Harper

    Department of Chemistry \& Biochemistry, University of California Los Angeles

  • Alex Levine

    Department of Chemistry and Biochemistry, University of California, Los Angeles, University of California, Los Angeles, Department of Chemistry \& Biochemistry, University of California Los Angeles, UCLA, Department of Chemistry \& Biochemistry