Up-and-down transformable embedded ink writing strategy for soft 3D architectures.

The fabrication of 3D soft material architectures is essential for advancing fields such as soft robotics, wearable technologies, and biological engineering. However, conventional embedded 3D printing is constrained by rheological complexity and nozzle-dependent structural limitations. Here, we introduce transformable embedded ink writing (TEIW), a 3D printing strategy that bypasses these issues by triggering rapid, autonomous self-assembly of 2D-printed patterns into predefined 3D structures. TEIW employs yield-stress inks within a Newtonian-like fluid bath, where net gravitational-buoyancy forces drive the filaments to go upward or downward. Through tailored density contrasts, controlled viscosity, and mechanical coupling between structural elements, complex shape transformation is directed with physical intelligence embedded in the printed structure itself, requiring no external intervention. This strategy demonstrates broad compatibility with materials including silicone elastomers, acrylate-based resins, and hydrogels, enabling applications spanning customizable microelectronics, perfusable networks, and cryptographically encoded devices. Furthermore, TEIW's ability to integrate various components in a single print establishes a platform for next-generation systems requiring spatiotemporal multi-material control.