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.
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.
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