Abstract
Background: Within the AdLap project, a versatile modular laparoscopy robotic platform, new multifunctional reusable instruments are being developed that often require different operational forces. The main goal of this study is to create an end effector grasper that amplifies pinching force in two stages: a low-transmission Phase 1 for gentle tissue handling and a high-transmission Phase 2 to apply a firm grip on rigid elements like needles when needed while keeping the activation force in the rod low. Methods: a mechanical force-adaptive phase controller was designed and implemented in a laparoscopic grasper, thereby eliminating the need for separate instruments by combining the functions of a low-force tissue grasper and a high-force needle holder. Results: a functional prototype of an integrated force amplifier was developed at a 3:1 scale, featuring a 3D-printed housing with all-metal internal components, achieving a Phase 1 transmission value of 0.33 and a Phase 2 transmission value of 0.45, resulting in a force amplification ratio of 1.34. Discussion: Force transmission efficiency during Phase 1 was measured at 66%, while the phase-switching efficiency was 57% indicating that the main requirement is met, with potential for further optimization with only minor adjustments and manufacturing of the parts. Integrating this compact mechanism offers advantages for both robotic operation and manual surgery as it reduces the activation load at the tip in the rod or cables during high pinch loading and thereby reducing wear in the steerable shaft. Conclusion: The proven design potential for rigid and flexible scopes with multi-functional end-effectors that might otherwise deform under loading or require end-effector changes between surgical actions.