Current challenges in tissue engineering include creating the extracellular environment, utilizing biochemical, mechanical, and structural cues to support cells and interact with them. Due to the lack of suitable manufacturing technologies, spatial control of these cues is currently limited. This study introduces Xolography, an emerging dual-color light sheet volumetric printing technology that can complete printing within minutes while achieving control over the structural and mechanical features of hydrogel-based photopolymers from the micro to macro scale. A water-soluble photoswitch photoinitiator system and a library of naturally derived, synthetic, and thermoresponsive hydrogels for Xolography are proposed.Centimeter-scale 3D structures with 20 μm positive features and ≈100 μm negative features were fabricated while controlling mechanical properties (compression modulus 0.2 kPa–6.5 MPa). Notably, switching from binary light projection to grayscale light projection enables spatial control of stiffness (0.2–16 kPa). As a proof of concept, grayscale Xolography was combined with thermo-responsive hydrogels to introduce reversible anisotropic shape changes beyond isochoric contraction. Ultimately, Xolography of live cell aggregates was demonstrated, laying the foundation for printing dynamic, cell-guiding environments with tunable structures and mechanical cues in a rapid, single-step process. Overall, these innovations open unique possibilities for Xolography in numerous biomedical applications.

Summary

In the field of tissue engineering, how to rapidly fabricate hydrogel scaffolds that combine micron-scale structural precision with controllable mechanical properties has always been a research hotspot. Recently, a study published in Advanced Materials demonstrated the great potential of the Xolography dual-color light sheet volumetric printing technology. This technique induces local photopolymerization through orthogonal dual-color light beams, allowing the printing of centimeter-scale hydrogel structures within minutes. The research team successfully developed a water-soluble photoswitchable initiator system and established a materials library that includes naturally derived, synthetic, and thermosensitive hydrogels. Through systematic process optimization, they achieved printing with forward structures at 20-micron resolution and channels of approximately 100 microns, while the material compression modulus could be adjusted over a wide range from 0.2 kPa to 6.5 MPa. Notably innovative is that, by introducing grayscale light projection technology, the researchers achieved spatial control of material stiffness during a single printing process, forming continuous stiffness gradients ranging from 0.2 to 16 kPa. Based on thermosensitive hydrogels, the team further demonstrated 4D printing capabilities, achieving reversible anisotropic deformation through local differences in crosslinking degree. The study demonstrated for the first time that Xolography can be used for bioprinting with cell aggregates; post-printing, cells maintained good viability and exhibited position-dependent behavioral differences within the scaffold. This research opens new avenues for the rapid fabrication of tissue engineering scaffolds with dynamic responsiveness and mechanical heterogeneity.

References:

DOI: 10.1002/adma.202410292

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