Active Particles in Polymer Networks Model Bacteria Behavior in Biofilms

Bacteria exert a hydrodynamic swim stress that present methods for infiltration and break up of biofilms, which are a large issue for medical device cleanliness. Active synthetic matter has also been shown to generate enough stress to drastically modulate the shape of a lipid membrane via tuning of the particle speed and membrane tension. We use active synthetic particles in a hydrogel to mimic the effect bacterial motion has on biofilms to better understand mechanisms for eradicating bacteria. Active platinum Janus particles are swollen with water and hydrogen peroxide fuel into a 4arm-PEG hydrogel that has either permanent (thiol-maleimide) or dynamic (boronic ester) crosslinks. By tuning the lifetime and permanence of the crosslinker, the swim ability can be dictated. In addition to biofilm elimination, this model active network exhibits a novel approach for polymer architecture design. Controlling the motion of the active particles during gelation could create pores for drug delivery or channels for ion conduction. Time-resolved rheometry is used to understand the viscoelastic changes made to the material and particle motion. Additionally, a novel microrheological magnetic tweezer setup is used to investigate the local scale properties of motion and crosslinker lifetimes.