Tomographic active optical trapping of arbitrarily shaped objects by exploiting 3-D refractive index maps

TL;DR

This paper presents a novel method for real-time optical manipulation of arbitrarily shaped particles by using 3-D refractive index maps to shape the trapping light field, enabling stable control without prior shape knowledge.

Contribution

It introduces a wavefront shaping technique combined with 3-D RI measurements to manipulate complex-shaped particles in real time.

Findings

Achieved stable 3-D control of arbitrarily shaped particles.

Demonstrated manipulation of biological and colloidal samples.

Enabled orientation and assembly control without prior shape information.

Abstract

Optical trapping can be used to manipulate the three-dimensional (3-D) motion of spherical particles based on the simple prediction of optical forces and the responding motion of samples. However, controlling the 3-D behaviour of non-spherical particles with arbitrary orientations is extremely challenging, due to experimental difficulties and the extensive computations. Here, we achieved the real-time optical control of arbitrarily shaped particles by combining the wavefront shaping of a trapping beam and measurements of the 3-D refractive index (RI) distribution of samples. Engineering the 3-D light field distribution of a trapping beam based on the measured 3-D RI map of samples generates a light mould, which can be used to manipulate colloidal and biological samples which have arbitrary orientations and/or shapes. The present method provides stable control of the orientation and assembly of arbitrarily shaped particles without knowing a priori information about the sample geometry. The proposed method can be directly applied in biophotonics and soft matter physics.