A high-throughput platform was developed to analyze struvite formation, finding that peptide addition modulates growth in a potentially favorable way.

Active Janus colloids are functional particles that combine two distinct chemical or physical surface properties. The anisotropic nature of this class of patchy particles allows them to harvest and redirect energy to create a local force that leads to autonomous motion. Modulating the surface forces experienced by or the responsiveness of a Janus particle's surface offer an avenue of further control. There are broad efforts in the community to advance the fundamental understanding of and engineer such control into active systems. This article aims to summarize recent work in catalytic active Janus colloids, peptide and polypeptide engineering and design, and present work showing how engineered polypeptides can be used to control motion of catalytic active particles. Experiments probing nonspecific effects are reviewed that measured the active motion of 5 μm catalytic Janus spheres in the presence of low molecular weight polyethylene glycol (PEG). Previous work has found that at infinitely dilute concentrations of particles, the addition of PEG in solution reduced particle propulsion speed. Further increasing particle concentration led to increased clustering at low concentrations of PEG, but clustering was then reduced at high concentrations of PEG. These results inspired work presented herein with 3 μm particles that shows platinum binding peptides that specifically attach to the platinum cap reduced the propulsion speed. These data support a pathway for using engineered peptides as tools for controlling the activity of catalytic active Janus particles. Overall, this article highlights how nonspecific and specific molecular interactions can achieve control in active systems.