# Propulsion and controlled steering of magnetic nanohelices

## TL;DR

This paper presents a simulation-based approach to design and control magnetic nanohelices for targeted propulsion and steering in fluid environments, overcoming thermal fluctuations at the nanoscale.

## Contribution

It introduces a quantitative simulation methodology for designing magnetic nanohelices that can be accurately propelled and steered despite Brownian motion.

## Key findings

- Successful propulsion of 30 nm magnetic nanohelices demonstrated
- Protocols for controlled steering at biological temperatures developed
- Fast transport achieved with external magnetic field manipulation

## Abstract

Externally controlled motion of micro and nanomotors in a fluid environment constitutes a promising tool in biosensing, targeted delivery and environmental remediation. In particular, recent experiments have demonstrated that fuel-free propulsion can be achieved through the application of external magnetic fields on magnetic helically shaped structures. The magnetic interaction between helices and the rotating field induces a torque that rotates and propels them via the coupled rotational-translational motion. Recent works have shown that there exist certain optimal geometries of helical shapes for propulsion. However, experiments show that controlled motion remains a challenge at the nanoscale due to Brownian motion that interferes with the deterministic motion and makes it difficult to achieve controlled steering. In the present work we employ quantitatively accurate simulation methodology to design a setup for which magnetic nanohelices of 30 nm in radius, with and without cargo, can be accurately propelled and steered in the presence of thermal fluctuations. In particular, we demonstrate fast transport of such nanomotors and devise protocols in manipulating external fields to achieve directionally controlled steering at biologically relevant temperatures.