Saeed Sokhanvar

A multifunctional PVDF-based tactile sensor for minimally invasive surgery

In this paper a multifunctional tactile sensor system using PVDF (polyvinylidene fluoride), is proposed, designed, analyzed, tested and validated. The working principle of the sensor is in such a way that it can be used in combination with almost any end-effectors. However, the sensor is particularly designed to be integrated with minimally invasive surgery (MIS) tools. In addition, the structural and transduction materials are selected to be compatible with micro-electro-mechanical systems (MEMS) technology, so that miniaturization would be possible. The corrugated shape of the sensor ensures the safe tissue grasping and compatibility with the traditional tooth-like end effectors of MIS tools. A unit of this sensor comprised of a base, a flexible beam and three PVDF sensing elements. Two PVDF sensing elements sandwiched at the end supports work in thickness mode to measure the magnitude and position of applied load. The third PVDF sensing element is attached to the beam and it works in the extensional mode to measure the softness of the contact object. The proposed sensor is modeled both analytically and numerically and a series of simulations are performed in order to estimate the characteristics of the sensor in measuring the magnitude and position of a point load, distributed load, and also the softness of the contact object. Furthermore, in order to validate the theoretical results, the prototyped sensor was tested and the results are compared. The results are very promising and proving the capability of the sensor for haptic sensing.

PVDF-Based Microfabricated Tactile Sensor for Minimally Invasive Surgery

This paper aimed to develop a miniaturized tactile sensor capable of measuring force and force position in minimally invasive surgery. The in situ measurement of tactile information is a step forward toward restoring the loss of the sense of touch that has occurred due to shift from traditional to minimally invasive surgeries. The sensor was designed such that it can sense low forces which could be comparable to those produced by pulsating delicate arteries, yet can withstand high forces comparable to grasping forces. The influence of some hidden anatomical features, such as lumps, voids, and arteries, on the stress distribution at the grasping surface was studied. In this paper, the capability of the sensor to determine and locate any point load was also investigated. The proposed sensor was designed and manufactured to be highly sensitive, using polyvinylidene fluoride (PVDF). The microfabrication procedure of the sensor, including corner compensation for toothlike projections and patterning of PVDF film, was discussed. The micromachined sensor was tested, and the experimental results were compared with the results of 3-D finite element modeling.

Design and microfabrication of a hybrid piezoelectric‐capacitive tactile sensor

Purpose – To measure the force applied to the tissue, the traditional endoscopic graspers might be equipped with a kind of tactile force sensor.Design/methodology/approach – This paper presents the design, analysis, microfabrication and testing of a piezoelectric and capacitive endoscopic tactile sensor with four teeth. This tactile sensor, which is tooth‐like for safe grasping, comprises a Polyvinylidene Fluoride, PVDF film for high sensitivity and is silicon‐based for micromachinability. Being a hybrid sensor, employing both capacitive and piezoelectric techniques, it is possible to measure both the static and dynamic loads. Another feature, to be considered in its design, is the ability to detect pulse. The proposed sensor can be integrated with the tip of any current commercial endoscopic grasper without changing its original design. It is shown that using an array of sensor units, the position of the applied load can still be determined.Findings – The static response of the sensor is obtained by appl...

Graphical Rendering of Localized Lumps for MIS Applications

Minimally invasive sugery (MIS) has increasingly been used in different surgical routines despite having significant shortcomings such as a lack of tactile feedback. Restoring this missing tactile information, particularly the information gained through tissue palpation, would be a significant enhancement to MIS capabilities. Tissue palpation is particularly important and commonly used in locating embedded lumps. The present study is inspired by this major limitation of the MIS procedure and is aimed at developing a system to reconstruct the lost palpation capability of surgeons in an effective way. By collecting necessary information on the size and location of hidden features using MIS graspers equipped with tactile sensors, the information can be processed and graphically rendered to the surgeon. Therefore, using the proposed system, surgeons can identify the presence or absence, location, and approximate size of hidden lumps simply by grasping the target organ with a smart endoscopic grasper. The results of the conducted experiments on the prototyped MIS graspers represented by graphical images are compared with those of the finite element models.

A micro-tactile sensor for in situ tissue characterization in minimally invasive surgery

This study presents and characterizes a micro-tactile sensor that can be integrated within MIS graspers. The sensor is capable of measuring contact forces and characterizing softness. The grasping forces are distributed normally, though in some cases concentrated loads also appear at the contact surfaces. In the latter case, the position of the concentric load can also be determined. This enables the sensor to detect hidden anatomical features such as embedded lumps or arteries. The microfabricated piezoelectric-based sensor was modeled both analytically and numerically. In a parametric study the influence of parameters such as length, width, and thickness of the sensor was studied using a finite element model. The sensor was microfabricated and tested using elastomeric samples. There is a good conformity between the experimental and theoretical results.

Graphical Reproduction of Tactile Information of Embedded Lumps for MIS Applications

Promising results of minimally invasive surgery (MIS) in the last two decades have been the main incentive of numerous researches to conquer some of the drawbacks of this procedure. Restoring the missing tactile information, especially the tissue palpation, is a significant enhancement in MIS capabilities. Tissue palpation is particularly important and commonly used in locating the embedded lumps. The present study is inspired by this essential limitation in MIS procedure and is aimed at developing a system to reconstruct the lost palpation capability of surgeons in an effective way. Having collected necessary information on the size and location of the hidden features using MIS graspers equipped with tactile sensors, we can process the information and graphically represent them to the surgeon. Therefore, the proposed system allows the surgeons to observe the presence or absence, location and approximate size of hidden lumps simply by grasping the target organ with smart endoscopic grasper. It is shown that using one array of the sensing elements; the proposed system can extract lump information including size and longitudinal location. The experimental results on the prototyped MIS graspers represented by graphical images conform to those of the finite element models.