Design of Novel Interlocked Bi-Layer NiTi Braided Stent with Ultra-Thin Walls for Urinary Tract Obstruction Treatment

Conventional ureteral stents often face a critical trade-off between radial support and lumen patency, compromising drainage performance under compression. To overcome this, we designed a novel interlocked bi-layer nitinol (NiTi) braided stent. A thread-inspired interlocking strategy between the inner and outer layers was achieved by introducing a thick NiTi wire into the inner layer, significantly enhancing interlayer bonding (64.10 ± 5.62 cN). The optimized stent featured an ultra-thin wall structure (0.31 ± 0.03 mm), which enabled a 29.03% larger lumen diameter while providing a 174.38% higher radial strength (2215.44 ± 42.87 cN) compared to commercial polyurethane (PU) ureteral stents. Moreover, it demonstrated superior flexibility, with a bending stiffness of 0.87 ± 0.07 N·mm2. Under simulated ureteral obstruction model (1.0 mm constant compression) with low renal pressure, the stent preserved 33.56% of its initial drainage rate, while the PU stent lost virtually all flow. Additionally, the retention force (24.08 ± 0.98 cN), optimized via J-end geometry, was equivalent to clinical standards. This study introduces a structurally reinforced, drainage-efficient ureteral stent that synergistically improves lumen patency, mechanical robustness, and anchoring performance. The proposed interlocked bi-layer braiding concept offers a scalable design strategy for next-generation stents and other minimally invasive tubular implants.