Evaluation of in vitro mechanical properties of stent polymers: experimental study

Background. Most comparisons of stent polymers rely on finished devices, where geometry and coating obscure the polymer's own contribution. Whether silicone and polyurethane surfaces stay different after prolonged water contact, and whether their mechanical gap changes once water enters the matrix, remains unclear. We aimed to characterize the physico-mechanical properties of ureteral stent polymers experimentally.,Methods. Flat polyurethane (45, 50 Shore A) and silicone (30, 50 Shore A) samples were pressed and tested for contact angle, swelling, hardness, Young's modulus and liquid penetration depth before and repeatedly during immersion in distilled water until each parameter plateaued (mean ± SD; descriptive statistics only).,Results. Silicone started markedly hydrophobic (93.4° at 50 Shore A) and plateaued within ~10 h, versus 25–30 h for polyurethane; at plateau silicone remained more hydrophobic (95° vs 79°). Swelling plateaued by ~87 h in both, but water uptake at 50 Shore A was over tenfold higher in silicone (2.2% vs 0.2%). Silicone's modulus was lower than polyurethane's at matched hardness and fell further after wetting, while polyurethane stiffness stayed stable. After 20 min, dye penetration reached 250 µm in silicone versus 160 µm in polyurethane — over half the wall thickness of a standard 6 Fr stent.,Conclusions. Silicone and polyurethane converge in wettability but diverge mechanically: silicone absorbs water and softens, polyurethane stays dry and stiff. Clinical tolerance of silicone stents thus appears driven mainly by bulk mechanics, so stiffness deserves as much attention as coating in stent design.