In this paper we investigate the fabrication process of a novel polymer based pressure micro-sensor for use in
manometric measurements in medical diagnostics. Review and analysis of polymer materials properties and polymer
based sensors has been carried out and has been reported by us elsewhere [1]. The interest in developing a novel polymer
based flexible pressure micro-sensor was motivated by the numerous problems inherent in the currently available
manometric catheters used in the hospitals. The most critical issue regarding existing catheters was the running and
maintenance costs [2]. Thus expensive operation costs lead to reuse of the catheters, which increase the risk for disease
transmission. The novel flexible polymer based pressure micro-sensor was build using SU-8, which is a special kind of
negative photoresist. Single-walled carbon nanotubes (SWCNTs) and aluminum are used as the sensing material and
contacting electrodes respectively. The pressure sensor diaphragm was first patterned on top of an oxidized silicon wafer
using SU-8, followed by aluminum deposition to define the electrodes. The carbon nanotube is then deposited using
dielectrophoresis (DEP) process. Once the carbon nanotubes are aligned in between these electrodes, the remaining of
the sensor structure is formed using SU-8. Patterning of SU-8 and release from the substrate make the device ready for
further testing of sensing ability. This research not only investigates the use of polymeric materials to build pressure
sensors, but also explores the feasibility of full utilization of polymeric materials to replace conventional silicon
materials in micro-sensors fabrication for use in medical environments. The completed sensor is expected to form an
integral part of a large versatile sensing system. For example, the biocompatible artificial skin, is predicted to be capable
of sensing force, pressure, temperature, and humidity, and may be used in such applications as medical and robotic
system.
In this work we investigate the use of polymer materials as a basis for fabrication of a novel type of pressure sensors for
use in medical diagnostics. Experience with solid-state micro-electromechanical systems (MEMS) sensors has proved
them to provide a number of desirable characteristics in sensory applications, including miniaturization and low
production cost. However, owing to their rigidity, and bio-incompatibility, the solid-state sensors are not ideally suited
for applications in biomedical implants and in-vivo diagnostics. They often require extra encapsulation protection, and
thus diminishing their sensitivity and selectivity. Polymeric materials such as polyimide have been for a number of years
utilized to manufacture flexible printed circuit board (FPCB) and membrane switches used in computer keyboards.
Related work on polymer electronics has shown feasible the fabrication of micro sensors using polymer materials. In this
paper we show that combining the polymer thick-film (PTF) technology with the MEMS micromachining process yields
a workable platform for the realization of a flexible sensor for pressure measurements. We will show simulation results
that establish the validity of the model and which will confirm the promise that these devices hold for future biomedical
instrumentations. Recent sensor research by another group demonstrated a multi-model tactile sensor which consists of
hardness, temperature, and thermal conductivity sensing features, all combined and built on a polymer substrate [1] and
[2]. Advantages of using polymer materials include flexibility, biocompatibility, robust characteristics, reduced
fabrication complexity and reduced production costs, as well as the use of environmentally friendly manufacturing.
In this paper we report on the development of a new disposable manometric catheter for diagnosis of functional
swallowing disorders. The function of this catheter is to measure the intrabolus and peak pressures occurring along the
esophageal tract during the swallowing process. Traditionally, in hospitals the water perfusion technique is used to
diagnose the disorder. Current manometric catheters developed elsewhere use a solid-state pressure sensor mounted
directly on a thin catheter to measure the pressure changes. Both types of catheters are re-usable due to the high running
cost, and this in turn increases the risk of contamination among patients, and creates hygiene problems. We have
developed a new disposable manometric catheter which consists of a MEMS-based pressure sensor. Recent laboratory
characterizations and hospital in-vivo tests show the new developed low cost disposable catheter prototype capable of
measuring pressure ranges of 0 to 100mmHg. The in-vivo tests have also shown the new catheter prototype capable of
measuring the peak pressure as well as the intrabolus pressure which is a very important parameter for doctors to carry
out the required diagnosis.
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