Enhanced Swimming Behavior of Active Hematite Microparticles

The emergence of autonomous, self-propelled active particles has been of interest for cargo delivery, environmental remediation, and as models for biological systems. However, designing highly active and cost effective microparticles is a remaining challenge. Hematite microparticles can be readily synthesized in a variety of shapes and exhibit photocatalytic behavior necessary for light-driven active motion, but they are limited due to the short lifetime of excited states. To mitigate this, we calcined the micro-particles and measured their activity by tracking the particle motion with optical microscopy. We calculated the mean-squared displacement (MSD) and found that increasing the calcination time results in a higher ensemble MSD for the hematite micro-particles. Calcined particles have an average 28-fold rise in MSD at 1-minute lag times. This simple approach makes hematite more accessible to key areas of soft matter and photocatalysis research.