UCSF

BACKGROUND: Conventional laparoscopic instruments provide limited dexterity in confined anatomical environments, whereas existing articulated designs rely on complex rigid joints or motorised actuation, increasing mechanical complexity and limiting miniaturisation. METHODS: A hybrid compliant-tendon laparoscopic instrument was developed to integrate articulated distal motion and active grasping within a 5 mm form factor. The compliant segment was fabricated from super-elastic Nitinol, and grasping was achieved using a tendon-pulley mechanism. The system was evaluated using nonlinear finite element analysis and experimental testing, including digital image correlation and benchtop force measurements. RESULTS: The mechanism achieved up to 75° articulation with mean model errors below 8%. The grasper produced a maximum force of 13.2 ± 0.47 N and maintained performance across articulation angles. Pull-out tests confirmed stable interaction with soft-tissue analogues. CONCLUSIONS: The proposed design demonstrates a compact, low-complexity approach for combining compliant articulation and tendon-driven grasping within a 5 mm surgical instrument.