Abstract

Development of Piezoresistive Tactile Sensors and a Graphical Display System for Minimally Invasive Surgery and Robotics

Masoud Kalantari, PhD
Concordia University, 2013

This PhD work presents a new tactile and feedback systems for minimally invasive
surgery (MIS)and robotics. The thesis is divided into two major sections: the tactile
sensing system, and the graphical display system.
In the tactile sensing system, piezoresistive materials are used as measuring elements.
The first part of the thesis is focused on the theoretical modeling of piezoresistive
sensing elements, which are semiconductive polymer composites. The model
predicts the piezoresistive behavior in semiconductive polymer composites, including
their creep effect and contact resistance. A single force sensing resistor (FSR) is, then, developed by using the semiconductive polymer composite materials. The developed
FSR is used in the structure of a novel tactile sensor as the transduction element.
The developed tactile sensor is designed to measure the difference in the hardness
degree of soft tissues. This capability of the sensor helps surgeons to distinguish different types of tissues involved in the surgery. The tactile sensor is integrated on the extremity of a surgical tool to provide tactile feedback from the interaction between surgical instruments and the tissue during MIS. Mitral valve annuloplasty repair by MIS is of our particular interest to be considered as a potential target for the use of the developed tactile sensor. In the next step, the contact interaction of the tactile sensor with soft tissues is modelled, parametrically. Viscoelastic interaction is considered between the tactile sensor and atrial tissue in annuloplasty mitral valve repair; and a parametric solution for the viscoelastic contact is achieved.
In addition to the developed sensor, a novel idea regarding measuring the indentation
rate, in addition to measuring force and displacement is implemented in a new
design of an array tactile sensor. It is shown that the indentation-rate measurement is
an important factor in distinguishing the hardness degree of tissues with viscoelastic
behaviour.
The second part of the thesis is focused on the development of a three-dimensional
graphical display that provides visual palpation display to any surgeon performing
robotic assisted MIS. Two matrices of the developed piezoresistive force sensor are
used to palpate the tissue and collect the tactile information. The collected data are processed with a new algorithm and graphically rendered in three dimensions.
Consequently, the surgeon can determine the presence, location, and the size of any
hidden superficial tumor/artery by grasping the target tissue in a quasi-dynamic way.