Frontal polymerization enabled monolithic fabrication of hydrogel microfluidic chips

Conventional microfluidic chips, fabricated from rigid polymers like polydimethylsiloxane, fail to recapitulate the dynamic and compliant nature of the native extracellular matrix (ECM), limiting their broader applications in biomedicine. In contrast, hydrogel-based microfluidic chips offer a promising alternative. However, their fabrication remains challenging due to the structural fragility, often requiring multi-step processes and secondary bonding. Here, we report a paradigm-shifting strategy for the monolithic fabrication of hydrogel-based microfluidic chips by leveraging the unique spatiotemporal control of aqueous frontal polymerization (FP). We employ 3D-printed polyvinyl alcohol (PVA) as a sacrificial template, which is encapsulated and preserved within a propagating polymerization front. The Transient reaction zone   rapidly solidifies the hydrogel matrix within minutes,   enabling the sacrificial template in its pristine state   without significant deformation. Subsequent removal of the template yields complex, high-fidelity, and leak-free microchannels, avoiding post-fabrication bonding. The resulting hydrogel chip exhibits robust mechanical properties, anti-swelling capacity, antibacterial activity, and superior biocompatibility, providing great potentials for biomedical applications. This FP-directed fabrication method provides great convenience for precise control over channel geometries and sizes, paving a new avenue for creating next-generation all- hydrogel biomimetic microfluidic platforms.