# A nanoscale robotic cleaner

## TL;DR

Tiny light-powered nanorobots can move and manipulate bacteria using laser polarization, acting as microscopic robotic cleaners.

## Contribution

Sub-micrometer nanorobots with plasmonic directional antennas enable efficient bacterial manipulation via laser polarization.

## Key findings

- Nanorobots reach propulsion speeds up to 50 μm/s with motion direction locked perpendicular to the linear polarization axis.
- Circularly polarized light pulses lift orientational degeneracy through spin–momentum transfer.
- Nanorobots can capture, transport, reversibly assemble, and release bacteria using opto-thermophoretic forces.

## Abstract

Photon-recoil–based actuation enables maneuvering of micro- and nanoscale objects without beam steering or tight focusing, mitigating system complexity and photodamage. Recent light-driven microdrones achieved full control in two dimensions using multiple laser fields; however, for many applications, sacrificing degrees of freedom allows substantial miniaturization and improved propulsion efficiency. Here, we demonstrate sub-micrometer nanorobots actuated by a plasmonic directional antenna that simultaneously provides propulsion force and orientation control. The nanorobots reach propulsion speeds up to 50 μm/s, with their motion direction intrinsically locked perpendicular to the linear polarization axis. Circularly polarized light pulses lift the resulting twofold orientational degeneracy through spin–momentum transfer. Using opto-thermophoretic forces, nanorobots efficiently capture, transport, reversibly assemble, and release bacteria. By sequencing linear and circular polarization states, they execute complex, high-precision trajectories to systematically sweep defined regions, functioning as light-driven robotic cleaners. This work expands the capabilities of nanorobots for biological manipulation and high-speed, localized sensing.

Submicron light-driven nanorobots powered by a plasmonic directional nanoantenna are controlled by laser polarization. They move rapidly along complex paths and capture, assemble, transport, and release bacteria, functioning as robotic cleaners.