BACKGROUND In natural orifice transluminal endoscopic surgery (NOTES) the peritoneal cavity is reached through natural orifices (mouth, rectus and transvaginal duct), by means of little cuttings in the walls of hollow organs. Due to narrow spaces, NOTES needs robotic systems to assure operation/movement precision and patient safety. Variable stiffness actuation (VSA) assures both requirements. METHODS The authors developed a grasper for NOTES, provided with VSA, to use as an end-effector for snail robot devices. The present paper deals with basic concepts of VSA and describes the design and architecture of the grasper. Characterization and functional experiments were performed and results analysed. RESULTS A finite element model developed for the actuator design was validated, performance grasper characteristic curves were obtained, VSA was validated, and the gripping capability of several objects was assessed. CONCLUSION The grasper satisfies technical design specifications. On the basis of the results obtained, a control system can be developed to test grasper in a simulated surgery environment.