Self-Propelled Liquid Crystal Droplets That Trigger Local Polymerization

Recent studies of active soft matter systems have unmasked universal physical principles that can describe non-equilibrium states found in both synthetic and living systems. For example, as liquid crystalline oil droplets dissolve into aqueous micellar solutions, they propel themselves via creation of interfacial tension gradients (Marangoni stresses) and exhibit behaviors such as chemotaxis. In this presentation, we will report an experimental study in which we have found that circulating flows inside self-propelled LC droplets trigger the release of inclusions (small aqueous microdroplets) from within the LC. Whereas electrical double layer and elastic forces initially trap the inclusions within the LC droplets, coalescence and coarsening of the inclusions that accompanies the motion of the self-propelled LC droplets ultimately lead to ejection of the inclusions from the LC droplets. By dissolving an initiator for polymerization within the inclusions, we show that it is possible to program self-propelled LC droplets to exhibit chemotaxis and then trigger polymerization at a targeted spatial location. Overall, our results provide fresh ideas for the design of active colloidal systems that respond to non-equilibrium stimuli with spatially and temporally targeted synthesis of polymers.