title: Design and evaluation of a variable stiffness manual operating platform for laparoendoscopic single site surgery (LESS).
abstract: BACKGROUND
  Most of the existing robotic platforms for LESS have workspace and load capacity weaknesses, because of the limitation of one single incision. We have developed a LESS manual operating platform of which the stiffness of the insertion tube is controllable.
  
  
  METHODS
  The system included two dexterous tool manipulators, a stereo-vision module and a variable stiffness insertion tube (VSIT), which was designed using phase-change material (mixed indium, gallium and stannum). Experiments to evaluate the effectiveness of the VSIT were set up. Peg transfer tasks and trajectory tracking tasks were conducted to assess the initial performance of the overall system.
  
  
  RESULTS
  The experimental results for stiffness characteristic suggested that the rigidity of the VSIT with a straight-forward pose was considerably increased by about four times in the rigid mode. Peg transfer tasks and trajectory tracking tasks were performed successfully with an average time of 97 s and 52 s, respectively.
  
  
  CONCLUSIONS
  The experimental results for stiffness characteristic showed that the manual operating platform had great promise for solving large workspace, high manipulation force and stability problems in LESS. The tool manipulators had the ability to achieve basic operations.
authors.affiliation: Key Lab for Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China.
authors.forename: Jinhua
authors.initials: J
authors.lastname: Li
authors.affiliation: Key Lab for Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China.
authors.forename: Xuejie
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Lab for Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China.
authors.forename: Jianchen
authors.initials: J
authors.lastname: Wang
authors.affiliation: Key Lab for Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Xing
authors.affiliation: Key Lab for Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China.
authors.forename: Shuxin
authors.initials: S
authors.lastname: Wang
authors.affiliation: Key Lab for Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China.
authors.forename: Xiangyun
authors.initials: X
authors.lastname: Ren
mesh_terms: D001696:Biomechanical Phenomena; D004867:Equipment Design; D005708:Gallium / Q000737:chemistry; D006801:Humans; D007204:Indium / Q000737:chemistry; D020706:Laparoscopes; D010535:Laparoscopy / Q000379:methods*; D008670:Metals / Q000737:chemistry; D019060:Minimally Invasive Surgical Procedures / Q000295:instrumentation; D012371:Robotics / Q000379:methods*; D013525:Surgical Instruments; D014001:Tin / Q000737:chemistry
chemical_list: D008670:Metals; D007204:Indium; D014001:Tin; D005708:Gallium
keywords: LESS; flexible instruments; high manipulation force; large workspace; manual operating; pancreatectomy; variable stiffness