Piezoelectric composite sensors which consist of a ferroelectric ceramic phase and a polymer binder have been the center of interest for offering a distributed sensing mechanism in many industrial applications. This study investigates the effect of PZT surface modification on the mechanical and piezoelectric properties of PZT/epoxy composite sensors. Lead zirconate titanate ceramic powder (PZT-5H) was surface modified to prepare a high PZT content (0-3) piezoelectric composite sensor. Functional groups of the modifiers grafted onto the PZT particle surface served as a bridge into the epoxy matrix, thus creating strong bonds between the matrix and PZT particles. This noticeably improved the dispersion of the PZT phase, allowing the use of large fractions of piezoactive component in the composite. It is demonstrated that the produced piezo-film shows an enhanced poling behavior in that it can be poled with lower voltages under reduced poling times. This is caused by greater levels of microstructural homogeneity in the modified films as well as alteration of interfacial charge characteristics using modifiers’ functional groups.
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.
The requirement to make low profile ohmic contacts to a piezo-resistive MEMS pressure sensor has highlighted
limitations of ultrasonic wire bonding technology. Wire bonding typically uses 25-50 μm diameter gold or aluminium
wire and ultrasonic welding to the contact pads of micro-electronic devices results in a contact wire proud of the pad
surface. If the application involves the MEMS pressure sensor and contacts being encapsulated, then repetitive changes
in pressure flexing the contact wires can lead to fracture.
A possible solution is to scale down laser welding technology to fuse materials at the micron scale. For this purpose a
precision ophthalmic surgical laser system has been modified to investigate optimum conditions for laser welding, both
at the micron scale and for the typical geometries involved. Typical requirements involve a cylindrical contact wire to
be bonded to a thin contact pad on the MEMS device. Since the pad size is of similar dimension to the wire, and the
requirement for a low profile stable configuration, a keyhole welding strategy is required.
The Nd:YAG based ophthalmic laser has been modified, the Q-switch removed and the output pulse width and energy
controlled principally via control of the flashlamp.
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.
Although coordinate metrology has reached a very high state of development concerning versatility and accuracy for
common engineering parts, a high precision capability with nano scale resolution and accuracy is often hard to achieve
when it is required to measure very small parts and features. The limiting component is the bulky probing system of
traditional coordinate measuring machines (CMMs). In order to satisfy increasing demand for highly accurate
geometrical measurements on small parts and small structures, a new measuring probe of high sensitivity and small
geometrical dimension with low contact forces needs to be developed. In this paper, a probing system, which combines a
Fibre Bragg grating (FBG) embedded optical fibre tactile probe with an optical sensing technique, has been used. A
novel simple wavelength shift demodulation system is tested which incorporates using the single mode light launched
from a laser diode (LD) forming an external cavity between the LD and the FBG sensor to detect the Bragg wavelength
shift induced by the strain on the FBG sensor. This demodulation method can be used to detect the strain-induced
wavelength shift of the FBG. A strain resolution of 0.6 με is achieved. With the sensor elements integrated into the probe
tip directly, the system sensitivity can be increased significantly.
Design for manufacturability, assembly and reliability of MEMS products is being applied to a multitude of novel
MEMS products to make up for the lack of "Standard Process for MEMS" concept. The latter has proved a major
handicap in commercialization of MEMS devices when compared to integrated circuits products. Furthermore, an
examination of recent engineering literature seems to suggest convergence towards the development of the design for
manufacturability and reliability of MEMS products. This paper will highlight the advantages and disadvantages of
conventional techniques that have been pursued up to this point to achieve commercialization of MEMS products,
identify some of the problems slowing down development, and explore measures that could be taken to try to address
those problems. Successful commercialization critically depends on packaging and assembly, manufacturability, and
reliability for micro scale products. However, a methodology that appropriately shadows next generation knowledge
management will undoubtedly address most of the critical problems that are hampering development of MEMS
industries. Finally this paper will also identify contemporary issues that are challenging the industry in regards to
product commercialization and will recommend appropriate measures based on knowledge flow to address those
shortcomings and lay out plans to expedient and successful paths to market.
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.
With the reduction in dimensions of products in the last decade, the need for highly accurate dimensional inspection and measurement increases, which requires down scaled measuring tools. The key element for a powerful down scaled dimensional measuring tool coordinate measuring machine is the downscaled probe. In order to satisfy the ongoing increasing demand for highly accurate geometrical measurements on small parts and small structures, a new measuring probe having high sensitivity and small geometrical dimension with low contact forces needs to be developed. In this paper, a novel probing system, which combines a FBG (Fibre Bragg Grating) embedded optical fibre tactile probe with an optical sensing technique, is proposed for down scaled 3D micro-CMMs. The Bragg wavelength shifts with the strain developed along the fibre once the fibre touches the surface of the part. With high-resolution interferometric wavelength demodulation technology, a resolution of 5nm could be achieved by the FBG integrated system. With the sensor elements integrated into the probe tip directly, the system sensitivity can be increased significantly for 3 dimensional measurements.
The wide utilisation of micro-systems has brought increasing attention into micro-fluidics in recent years. When the size and mass of a device are scaled down, forces which used to be ignored may become dominant in the performance of a micro system. This paper studies the behaviour of fluid responding to travelling sinusoidal waves imposed by a micro actuator. The thickness of the fluid between the wave surface and the substrate is 20 microns, and the wavelength is 50 microns. The model is developed and implemented in ANSYS. The nonlinearities of the flow exist in both X and Y directions. A stable thrust force can be generated by the moving waves. The direction of the thrust force is opposite to the direction of the travelling wave. The magnitude of the thrust force is related to fluid viscosity, wave amplitude, and wave frequency. As this force is highly predictable and controllable, it can be used to propel a micro device working in thin tubes filled with fluid. The principle could also be applied to non-Newtonian fluid, although the flow will be more complicate.
In the last decade the general miniaturisation of complex products has lead to an increased importance of high precision machining and assembly. Together with increasing precision of products, the need for highly accurate dimensional inspection increases. CMMs (Coordinate Measuring Machines), as a versatile and widespread dimensional metrology tool, can efficiently perform complex measurement with a resolution of about 0.1μm and a repeatability of about 0.3μm. The existing probes for CMMs tend to be very bulky and result in high probing forces for geometrical measurements of high accuracy on small parts. In this paper, an economical flexible method, which is based on optical fibre splicer, is proposed to fabricate an integrated micro scale silicon probe with spherical tip for micron CMMs. Based on Taguchi method, a combination of optimised process parameters has been obtained to control the fabrication conditions that will ensure the manufacturing of tips of a high and consistent quality. With proper control of the process parameters, an optic fibre probe tip with the diameter dimension in the range of 200 to 400μm is achieved and there is a great potential to fabricate a smaller tip with a diameter of 50-100μm in the future.
This paper presents a novel ultrasonic transducer which can be used as a liquid ejector to release drug. The ultrasonic transducer is based on the design of a flextensional transducer, which is composed of interdigital piezoelectric rings and a vibration membrane. The device works at an axisymmetric resonant mode to produce maximum amplitude at the center of the vibration membrane in axial direction. For the usage of multi piezoelectric rings, the flexural plate waves can be generated by applying two out-of-phase signals. The power consumption is of primary importance in the design of this device and the usage of single-ring or multi-ring piezoelectric material instead of bulk piezo material can therefore reduce the power consumption. An optimum working frequency, at which least power is required by the device, can be found by the piezoelectric, coupled field capability of the ANSYS/Multiphysics product.
Although coordinate metrology has reached a very high state of development concerning versatility and accuracy for common engineering parts, a high precision capability with nano scale resolution and accuracy is often hard to achieve when it is required to measure very small parts and features. The limiting component is the bulky probing system of traditional CMMs (coordinate measuring machines). In order to satisfy increasing demand for highly accurate geometrical measurements on small parts and small structures, a new measuring probe of high sensitivity and small geometrical dimension with low contact forces needs to be developed. In this paper, a novel probing system, which combines a FBG (Fibre Bragg Grating) embedded optical fibre tactile probe with an optical sensing technique, has been proposed. With the sensor elements integrated into the probe tip directly, the system sensitivity can be increased significantly. A preliminary theoretical analysis of the sensitivity of the FBG fibre sensor under axial and lateral end point loading has been presented and the results show that this micro scale probe has great potential to realize a resolution of 1nanometer on geometrical measurement of small parts.
Product design is the most important stage in the course of product development. All the important decision-making regarding manufacturing and assembly is made during this period. Concurrent engineering (CE) has been proposed to facilitate the whole development processes by using multi-disciplinary team-work. Under the concept of CE there is a need to provide the designers an expert system to investigate their design in the early stage of design. In this paper the construction of a product design simplification system has been explored and a prototype system has been developed. The system can be used to evaluate product design on the basis of design for assembly (DFA) principles. Design simplification can be accomplished by three approaches. The first uses the three criteria of Boothroyd and Dewhurst's Methodology, the second examines the functional implication of parts and the third considers if a part is secured after assembly. The system will give the designer advice according to the evaluation results. All the rules in the rule-base are derived from the expertise in DFA field. On the basis of the implementation of this prototype system further research directions are also suggested.
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