The Newsletter of the
Advanced Medical Devices
project (AMD-3) of the
Institute of Robotics and
Intelligent Systems, a
Federally Funded Network
of the Centres of Excellence

This prototypal laparoscopic stand has met all these initial design requirements:
     a) Spherical movement at the remote center of rotation.
     b) The two arms reach the entire work-space (350x500mm).
     c) Effective locking of all the joints with sufficient stiffness.
     d) Free manipulation of the arms and wrists through their entire proscribed range of movements.

Experimental feedback for this prototype was obtained at the animal surgical lab of the Jack Bell Centre during training sessions. The feedback was very positive. Surgeons appreciated the greater freedom of movement, the decreased interference of the wrist mechanisms, and the sufficient locking of joints.

  Suturing Device

Considering the fact that current laparoscopic tools and instruments are in the range of 5 to 12mm, we have been working on the possibility of a 12mm version for the next stage of prototyping and miniaturization. This stage proves quite challenging, both in terms of precision machining, as well as obtaining suppliers for special parts such as timing belts or bevel gears.

Several types of timing belts have been studied as candidates for the actuation belt. For example, metallic timing belts were considered as a promising alternative, since they are much thinner than plastic belts, but are much stiffer to bend around the desired path. Another alternative is a polyester flat belt with Neoprene coating to be converted to a timing belt. The open loop configuration of this kind of belt provided satisfactory results.

  A Knotting Mechanism

One of the most time consuming tasks in endosurgery is tying sutures. A design concept has been proposed and developed which can semi-automate certain motions associated with the knotting task. The design allows creation of the relative rotation and sliding which are associated with most types of knots. The prototype can be fitted through 10 mm diameter trocars.

  Tactile Sensor

Endoscopic graspers being used today do not have any sensors built into them. The grasper's lack of sensitivity hinders the surgeon's efforts to manipulate the tissue safely, and laparoscopic operations remain based on remote manipulation.

The AUD-3 group has developed a prototype of a piezoelectric micromachined tactile sensor that could be incorporated in to the gripping ends of an endoscopic surgical tool. This tactile sensor enables the surgeon to detect the magnitude and the position of the applied force on a tissue during the endoscopic surgery. This sensor prototype has a rigid tooth-like surface similar to the present model.

  Grasper with Haptic Interface

Due to the long stem and the intermediate mechanism, current endoscopic graspers do not give the surgeon any direct sensation of tissues. As a result, tissues and organs can be injured due to excessive grasping forces. A design concept for a grasper has been proposed and developed which limits the amount of force that gets transmitted from the handle of the grasper to its tip. In addition, the design allows the surgeon to tune the magnitude of force transmission based on his/her gripping force capabilities. The design is based on the notion of a tunable spring and direct sensation of the gripping forces.