Remodeling and self-healing of individual amyloid tactoids via multiphoton absorption

Colloidal self-assembly can typically be controlled only globally, at $\ge$ 10¹ μm scale, such as in liquid-liquid crystalline phase separation (LLCPS) of anisotropic tactoidal droplets. Here, we introduce a stimuli-responsive approach allowing a fully reversible structural control of LLCPS morphologies at the individual droplet level. Using amyloid-based tactoids and multiphoton absorption with localized photothermal effect, we can cut, ablate, and self-heal individual tactoids, and -when desired- print, erase, and store structural information within at sub-micron resolution. We exploit the nematic-isotropic-nematic transition within single tactoids to locally melt the liquid crystalline (LC) order into the isotropic phase, leaving unchanged the bulk dispersion structure. The locally melted nematic field recovers its ground-state LC order within minutes after the exposure, showing both self-healing and short-term memory-storage features. Furthermore, hybrid cholesteric tactoids functionalized by guest nanoparticles can be re-modeled into new tactoids with different symmetry and functionalities, for example, featuring laser-induced fluorescent encoding. These results introduce a general strategy to direct phase separation-within-phase separation and to store, control, and engineer information at the sub-micron level in heterogeneous complex fluids.