Highly stretchable membranes and robust liquid marbles based on electromechanically stabilized aero-GaN tetrapodal...

Hollow aero-GaN tetrapods containing ultrathin residual ZnO layers on their inner walls spontaneously assemble at air-water interfaces into highly porous, mechanically compliant membranes and robust liquid-marble shells. Their four-armed geometry promotes mechanical interpenetration, while the nanometre-thick hollow GaN/ZnO walls provide pronounced flexibility and structural adaptability. Under hydrostatic loading, the projected membrane area increased from 176 to 255 mm², corresponding to an areal strain of 44.9% and an equivalent engineering linear strain of 20.4%. Reversible deformation was demonstrated over 17 consecutive loading-unloading cycles, during which the membrane repeatedly recovered its initial shape without visible rupture. Liquid marbles formed from aero-GaN tetrapods exhibited reproducibly higher threshold forces and breakdown pressures than ZnO-tetrapod controls, with an average breakdown pressure approximately 1.72 times higher. This improvement is attributed primarily to mechanical interpenetration and the compliant hollow-wall architecture, while deformation-induced piezoelectric, flexoelectric, and dielectric polarization may provide an additional contribution to network cohesion. When confined in the curved meniscus near a hydrophobic wall, self-propelled aero-GaN liquid marbles displayed stable forward-reverse rotational oscillations over successive cycles, with a mean period of 0.837 ± 0.027 s. These dynamics are consistent with a Marangoni-driven mechanism involving cyclic inversion of the effective surface-tension gradient. The results establish aero-GaN tetrapodal assemblies as promising adaptive inorganic membranes and active liquid marbles combining large reversible deformation, enhanced mechanical robustness, and stable interfacial dynamics.