Run-and-tumble dynamics of active giant vesicles

Cell-inspired architectures offer a promising path toward self-regulating and functional artificial microswimmers. Here, we fabricate Janus lipid vesicles with reconfigurable motion enabled by membrane fluidity. Depending on temperature and their membrane composition giant unilamellar vesicles (GUVs) can undergo spontaneous phase separation, forming Janus-like structures at room temperature. We demonstrate that due to their Janus architecture, they self-propel under external electric fields as their colloidal analogues. Interestingly, their fluid membrane coupled to the electric field induces transitions between laterally phase separated and disordered reconfigured states, characterized by 2D domain analysis. These transitions drive distinct run-and-tumble dynamics, with runs linked to phase-separated Janus states of the GUV and tumbles to transient disorder of the lipid domains, leading to an instantaneous halt of their activity due to loss of the Janus asymmetry. We identify a faster reorientation timescale decoupled from thermal effects provoked by the tumble events. This cell-inspired system offers a novel strategy for developing motile artificial cells and programmable microswimmers.