Liquid Printing in Nanochitin Suspensions: Interfacial Nanoparticle Assembly Toward Volumetric Elements, Organic Electronics and Core-Shell Filaments.

A nanoparticle-nanoparticle assembly is introduced using electrostatic complexation to precisely control volumetric structuring at the water/alcohol interface. In this system, an aqueous graphene oxide (GO) ink interacts electrostatically with partially deacetylated chitin nanofibers (mChNF), modified with benzophenone and dispersed in 1-butanol, which serves as the external phase. Upon extrusion of the GO ink, a jammed interfacial network forms, stabilizing the printed patterns within the external suspension, which provides suitable viscoelasticity for support-free printing. This approach is further extended to inks incorporating metal-organic frameworks or cellulose nanoparticles, demonstrating the advantages of mChNF as a stabilizer. Additionally, by incorporating a conductive polymer, the inks can be tailored for programmable and conductive patterning, opening new opportunities in liquid electronics and reconfigurable systems. Finally, GO inks containing an anionic polyelectrolyte (sodium alginate) undergo osmosis-driven solidification, facilitating the demolding of high-fidelity 3D structures formed by the printed threads of struts. These structures exhibit coreshell morphologies and high mechanical strength (∼175 MPa at 4% strain). Overall, this liquid-in-liquid fabrication approach, enabled by the integration of mChNF in the external phase, unlocks new possibilities for the design of versatile and multifunctional materials.