Optical funnel to guide and focus virus particles for X-ray laser imaging

TL;DR

This paper demonstrates an optical funnel that uses photophoretic forces to focus aerosolized virus particles, enhancing their delivery for X-ray imaging with potential applications in biomolecular studies.

Contribution

It introduces and experimentally validates a high-aspect-ratio optical funnel for concentrating virus particles in low-pressure environments, improving sample delivery for XFEL imaging.

Findings

Achieved threefold transverse compression of aerosolized viruses

Demonstrated formation of a high-aspect-ratio optical funnel

Paved the way for more efficient XFEL sample delivery

Abstract

The need for precise manipulation of nanoparticles in gaseous or near-vacuum environments is encountered in many studies that include aerosol morphology, nanodroplet physics, nanoscale optomechanics, and biomolecular physics. Photophoretic forces, whereby momentum exchange between a particle and surrounding gas is induced with optical light, were recently shown to be a robust means of trapping and manipulating nanoparticles in air. We previously proposed a photophoretic "optical funnel" concept for the delivery of bioparticles to the focus of an x-ray free-electron laser (XFEL) beam for femtosecond x-ray diffractive imaging. Here, we describe the formation of a high-aspect-ratio optical funnel and provide a first experimental demonstration of this concept by transversely compressing and concentrating a high-speed beam of aerosolized viruses by a factor of three in a low-pressure environment. These results pave the way toward improved sample delivery efficiency for XFEL imaging experiments as well as other forms of imaging and spectroscopy.