Stability of co-annular active and passive confined fluids

We investigate the stability of two configurations: a passive viscous Newtonian droplet immersed in an active nematic liquid crystal, and an active nematic droplet surrounded by a passive layer, both under circular confinement. Our results reveal how capillary, active, elastic, and viscous stresses interact to govern droplet dynamics. These findings may inform our understanding of diverse biological systems featuring interfaces between active and passive fluids, from droplets in bacterial suspensions to subcellular compartments within the cytoplasm and cell nucleus.