LipoGels: Robust Self‐Lubricating Physically Cross‐Linked Alginate Hydrogels Embedded with Liposomes

Abstract The exceptional lubricity in living systems has stimulated wide scientific interest in the design of biomimetic lubricants. Here, a sodium alginate hydrogel physically cross‐linked with divalent cations (Ca 2+ ), incorporating ≈100 nm 1,2‐dipalmitoyl‐ sn ‐glycero‐3‐phosphocholine liposomes in trace amounts (≈0.004–0.08 wt% lipids), which are termed “LipoGels”, is optimized to overcome gelation shrinkage to generate a homogeneous and smooth surface. Cryogenic scanning electron microscopy reveals the compact porous gel structure with embedded liposomes, and confocal fluorescent microscopy reveals a uniform distribution of liposomes in the gel. The LipoGels demonstrate robust mechanical strength, with an elastic modulus G ʹ > 200 kPa and a Young's modulus E ≈1 MPa from rheology and microindentation measurements, respectively. Small‐angle neutron scattering deduces a classic de Gennes’ mesh size of ξ ≈3.8 nm for the polymer network, consistent with that estimated from the rheology results. The underwater friction coefficient of liposome–alginate hybrid LipoGels, evaluated in the sphere‐on‐flat geometry with a tribometer, is as low as μ ≈0.02 at a maximum contact pressure of 0.45 MPa. These results offer nanostructural insights into the hybrid liposome–alginate hydrogels, prepared by facile physical cross‐linking, demonstrating their potential as biomimetic lubricants, also with encapsulation capacities for functional additives.