On-tip laser integration of 3D liquid-diode microvalves for disturbance-resilient drug infusion

Reliable unidirectional fluid transport in microscale conduits remains a long-standing challenge for minimally invasive medicine, where transient pressure fluctuations often induce backflow, clogging, and cross-contamination. In biological microcirculation, such instabilities are efficiently suppressed by flexible venous valves. However, translating these mechanically active structures into artificial microcatheters is impractical at extreme aspect ratios because of fabrication, alignment, and reliability concerns. Herein, we introduce a geometry-encoded flow-regulation strategy enabled by an on-tip femtosecond laser fabrication method, demonstrating a 3D Tesla microvalve to be directly inscribed along the curved tip of microscale catheters (inner diameter less than 100 µm). By implementing in situ optical alignment during writing, conformal fabrication of complex microarchitectures is achieved. The microvalve produces functional “liquid-diode” behavior through asymmetric viscous and inertial dissipation. The integrated Tesla valve restores flow rectification under low-Reynolds-number conditions, strongly suppressing reverse flow while maintaining low forward resistance. Experiments and simulations reveal vortex-mediated energy dissipation in the reverse direction (reduced by 73.5% during flow initiation and 82.0% during termination), converting unstable infusion into robust, unidirectional transport. This work demonstrates that microfluidic flow stability can emerge from geometry alone when coupled with precise laser-enabled on-tip integration. The proposed approach establishes a general framework for function-oriented biomimicry in extreme-aspect-ratio medical devices, with implications for precision drug delivery, implantable microfluidics, and long-term minimally invasive therapies.