Scaffold‐Free Living Cellular Structure With Omnidirectional Architectures

Scaffold‐free tissue engineering aims to recapitulate native cellular organization, yet constructing structurally stable tissue architectures beyond planar geometries remains challenging. Here, we show that hydrogel lumen confinement, created through aqueous‐in‐aqueous embedded bioprinting, guides the self‐assembly of high‐density cells into mechanically stable, scaffold‐free cellular filaments with omnidirectional architectures. By extruding cell‐laden ink at densities up to 1.0 × 10 8 cells mL −1 into a sodium alginate matrix, rapid interfacial coacervation generates hollow hydrogel lumens in a single step under entirely aqueous, phototoxicity‐free conditions. Within these lumens, densely packed cells spontaneously organize into continuous cell‐only filaments that exhibit solid‐like mechanical behavior with an elastic modulus of approximately 40 kPa, comparable to conventional hydrogel scaffolds yet composed entirely of living cells and their autologous extracellular matrix. These filaments display uniformity, intrinsic self‐healing capability, and sustained biological function, as evidenced by glucose‐responsive insulin secretion from MIN6 cells. The mechanical strength and seamless merging capacity of these filaments enable their use as building blocks for higher‐order assembly through folding, weaving, and winding into woven, entangled, and molded three‐dimensional configurations. This confinement‐guided self‐assembly strategy bridges the gap between scaffold‐free cellular construction and structurally complex tissue architecture, establishing a versatile platform for omnidirectional biofabrication of living cellular constructs.