(63d) The Impact of Bubbles during the Directed Assembly of Magnetic Janus Particle Microswimmers.

Biological bubbles play an important role in the dynamics of microbial systems such as bacteria and algae. However, the biological complexity of these systems makes it difficult to model how bubbles form, grow, and affect their environment. Janus microswimmers – spherical particles with a catalytic platinum cap that decomposes hydrogen peroxide into oxygen and water - can be used as simple models for a bubble-generating system. Magnetic Janus microswimmers, with both iron and platinum caps, add a simple attractive force between particles, causing them to assemble once magnetized. Here, quasi-two-dimensional systems of magnetic Janus microswimmers are studied in open-air cells for varying concentrations of hydrogen peroxide fuel and liquid film thicknesses. Particle aggregation and bubble nucleation and growth are tracked, demonstrating that film thickness directly influences bubble size, which in turn affects cluster morphology. This study provides insight into the mechanism of bubble-driven self-assembly and could inform models of synthetic and biological systems.