Photocatalytic magnetic microgyroscopes with activity-tunable precessional dynamics

TL;DR

This paper introduces an active magnetic microgyroscope driven by photo-activated catalysis and magnetic fields, demonstrating enhanced precessional dynamics through combined experimental and theoretical analysis.

Contribution

It presents the first active magnetic microgyroscope utilizing light-induced catalytic reactions to control and enhance its precessional motion.

Findings

Activity from catalytic reactions increases gravitational torque.

The combined forces influence the precessional behavior.

Experimental results align with theoretical models.

Abstract

Magnetic nano/microrotors are passive elements that spin around an axis due to an external rotating field while remaining confined to a close plane. They have been used to date in different applications related to fluid mixing, drug delivery or biomedicine. Here we realize an active version of a magnetic microgyroscope which is simultaneously driven by a photo-activated catalytic reaction and a rotating magnetic field. We investigate the uplift dynamics of this colloidal spinner when it stands up and precesses around its long axis while self-propelling due to the light induced decomposition of hydrogen peroxide in water. By combining experiments with theory, we show that activity emerging from the cooperative action of phoretic and osmotic forces effectively increase the gravitational torque which counteracts the magnetic and viscous ones, and carefully measure its contribution.