Photonic Crystal Optical Tweezers

TL;DR

This paper introduces a novel optical method using photonic crystal nanostructures to trap, rotate, and align microscopic particles and cells with high efficiency and low light intensity, advancing biological and nanotechnological applications.

Contribution

It presents a new purely optical technique employing photonic crystal nanostructures for particle manipulation, including rotation and alignment, with detailed simulations explaining the underlying mechanisms.

Findings

Efficient trapping of particles from 10 um to 190 nm.

Successful rotation and alignment of non-spherical particles and cells.

Low optical intensity required for manipulation, as low as 17 uW/um^2.

Abstract

Non-invasive optical manipulation of particles has emerged as a powerful and versatile tool for biological study and nanotechnology. In particular, trapping and rotation of cells, cell nuclei and sub-micron particles enables unique functionality for various applications such as tissue engineering, cancer research and nanofabrication. We propose and demonstrate a purely optical approach to rotate and align particles using the interaction of polarized light with photonic crystal nanostructures to generate enhanced trapping force. With a weakly focused laser beam we observed efficient trapping and transportation of polystyrene beads with sizes ranging from 10 um down to 190 nm as well as cancer cell nuclei. In addition, we demonstrated alignment of non-spherical particles using a 1-D photonic crystal structure. Bacterial cells were trapped, rotated and aligned with optical intensity as low as 17 uW/um^2. Finite-difference time domain (FDTD) simulations of the optical near-field and far-field above the photonic crystal nanostructure reveal the origins for the observed results. This approach can be extended to using 2-D photonic crystal nanostructures for full rotation control.