Active Matters in Structured Liquids*

The motion of active matter is the basic form of locomotion in biology, a vital ingredient in many functions of cells, and an essential design challenge in nanorobotics. Here, we integrated active matter into structured liquids to harness its motions to perform work on liquid interfaces. The structured liquids, produced by interfacial jamming of nanoparticle-surfactants (NPSs), are reconfigurable and therefore provide an ideal platform for generating active energy-consuming systems. The liquid shape will evolve and respond to external stimuli when the interfacial tension is sufficiently low. 3D active fluids consisting of microtubules and kinesins are directly attached to water-oil interfaces. The ultralow interfacial tension of the structured liquid is achieved by proper selection of NPSs. The interaction between active matter and liquid interfaces is observed in real time by confocal microscopy. This strategy would provide a route to a new class of biomimetic, reconfigurable, and responsive materials, delivering mechanical responses unlike those of conventional materials.