Pulling and lifting macroscopic objects by light

TL;DR

This study demonstrates the first direct observation of light-induced negative forces capable of pulling and lifting centimeter-sized objects using radiometric effects, opening new possibilities for macroscopic optical manipulation.

Contribution

It provides the first direct measurement and demonstration of optical pulling forces on macroscopic objects, expanding the scope of optical manipulation techniques.

Findings

Achieved pulling and lifting of centimeter-sized objects with light.

Measured a large force (~4.4 μN) overcoming gravity.

Enabled rotation of a motor with curved vanes at 600 rpm.

Abstract

Laser has become a powerful tool to manipulate micro-particles and atoms by radiation pressure force or photophoretic force, but optical manipulation is less noticeable for large objects. Optically-induced negative forces have been proposed and demonstrated to pull microscopic objects for a long distance, but are hardly seen for macroscopic objects. Here, we report the direct observation of unusual light-induced attractive forces that allow pulling and lifting centimeter-sized light-absorbing objects off the ground by a light beam. This negative force is based on the radiometric effect on a curved vane and its magnitude and temporal responses are directly measured with a pendulum. This large force (\~4.4 {\mu}N) allows overcoming the gravitational force and rotating a motor with four-curved vanes (up to 600 rpm). Optical pulling of macroscopic objects may find nontrivial applications for solar radiation-powered near-space propulsion systems and for understanding the mechanisms of negative photophoretic forces.