A number of photovoltaic technologies have been developed for large-scale solar-power production. The single-crystal first-generation photovoltaic devices were followed by thin-film semiconductor absorber layers layered between two charge-selective contacts, and more recently, by nanostructured or mesostructured solar cells that utilize a distributed heterojunction to generate charge carriers and to transport holes and electrons in spatially separated conduits. Even though a number of materials have been trialed in nanostructured devices, the aim of achieving high-efficiency thin-film solar cells in such a manner as to rival the silicon technology has yet to be attained. Organolead halide perovskites have recently emerged as a promising material for high-efficiency nanoinfiltrated devices. An examination of the efficiency evolution curve reveals that interfaces play a paramount role in emerging organic electronic applications. To optimize and control the performance in these devices, a comprehensive understanding of the contacts is essential. However, despite the apparent advances made, a fundamental theoretical analysis of the physical processes taking place at the contacts is still lacking. However, experimental ideas, such as the use of interlayer films, are forging marked improvements in efficiencies of perovskite-based solar cells. Furthermore, issues of long-term stability and large-area manufacturing have some way to go before full commercialization is possible.
Chronic wounds, such as venous leg ulcers, can be monitored non-invasively by using modern sensing devices and wireless technologies. The development of such wireless diagnostic tools may improve chronic wound management by providing evidence on efficacy of treatments being provided. In this paper we present a low-power portable telemetric system for wound condition sensing and monitoring. The system aims at measuring and transmitting real-time information of wound-site temperature, sub-bandage pressure and moisture level from within the wound dressing.
The system comprises commercially available non-invasive temperature, moisture, and pressure sensors, which are interfaced with a telemetry device on a flexible 0.15 mm thick printed circuit material, making up a lightweight biocompatible sensing device. The real-time data obtained is transmitted wirelessly to a portable receiver which displays the measured values. The performance of the whole telemetric sensing system is validated on a mannequin leg using commercial compression bandages and dressings. A number of trials on a healthy human volunteer are performed where treatment conditions were emulated using various compression bandage configurations.
A reliable and repeatable performance of the system is achieved under compression bandage and with minimal discomfort to the volunteer. The system is capable of reporting instantaneous changes in bandage pressure, moisture level and local temperature at wound site with average measurement resolutions of 0.5 mmHg, 3.0 %RH, and 0.2 °C respectively. Effective range of data transmission is 4-5 m in an open environment.
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 . 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 . 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
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  and
. 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.
For quite some time implantable electronic devices have been a topic of intense research. Such devices play a vital role in saving lives. Batteries were to the main source of power for micro implants in the body, and the quest has been to realize long life batteries. However, the battery size and limited lifetimes have fuelled the search for more practical alternatives1. Hence the concept of Transcutaneous Energy Transmission (TET) has become a major aim of research in microtechnology for supplying power to micro implants. Among many other endeavours, research to optimize the efficient wireless power transmission to implants2, thereby increasing lifetime of the implant and the comfort of the patient, has never been more intense.
In this paper we propose to present research findings related to determination of parameters for optimal design of the power transmission system, including frequency spectrum, orientation, and component sizes. We have particularly focused on coil design implementation. Coil design is critical to efficient power transmission and data reception. We have looked at the two spiral geometries3 with different aspect ratios. Coupling factor, mutual inductance of the coil, quality factor Q, and optimal distance between transmitter and receiver units are to be investigated. Electromagnetic simulation is to be carried out using EM3DS simulation tool for integrated inductor design. It gives us an estimation of the coupling efficiency of the coil and power efficiency of the link at specified design geometries.
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.
Deformable grating light modulator (GLM) also known as grating light valve (GLV) is a Micro-Opto-Electro
Mechanical System (MOEMS) grating which is originally presented as a deformable grating optical modulator by
Solgaard in 19921. Since then it has been developed for uses in various applications such as in display technology,
graphic printing, lithography and optical communications2, 3. We are proposing the use of deformable grating light
modulators as dispersive element to de-multiplex optical input signals in a wavelength selective switching system which
is originally presented by Mechels and Muller (2003) as a 1D MEMS-based wavelength switching system4. In this paper,
we discuss the performance of the grating system in various geometries and designs supported with numerical
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.
We present the design and fabrication methods for a piezoresistive pressure sensor intended for use in biomedical applications and in particular, pharyngeal manometry. Design requirements are investigated for the sensors size, pressure range and frequency response. The piezoresistive effect is investigated to determine the crystallographic orientation of the substrate and the position of the piezoresistive elements on the surface of the chip. A design calculation method is derived, and a design approach is proposed that satisfy the requirements of the application. Finally a brief description is given of the fabrication processing steps that could be utilised to realise this design.
Recently, advances in fabrication accuracy and decreasing feature size have lead to the application of piezoresistive pressure sensors to more challenging and confined environments. A particularly promising area has been miniature manometric catheters for invivo diagnostics. Many monolithic circuit designs have been proposed with this in mind, promising to deliver accuracy, increased sensitivity, multiplexing capacity and extremely reduced sizes. However, the delivery of a complete and commercially viable diagnostic device requires the consideration of many extended and interrelated variables dependent on the specific use of the device in the medical field. When designing the readout circuitry considerations may include the cost, size, complexity, manufacturing method, required accuracy, and durability of each component within the system. These factors influence the nature of support circuitry, and determine the level of integration required. This paper briefly describes the characteristics of piezoresistive Wheatstone bridge pressure sensors, and discusses options and considerations in the design of support circuitry for use in biomedical manometric catheters.
Mechanical instability and stiction of surface structures are troublesome problems in the microfabrication of microelectromechanical systems (MEMS). They are particularly critical when separation gaps are in the sub-micrometer scale. Fabrication-related stiction is usually the result of the rinse-and-dry procedure following the sacrificial layer etch in the structure-release process. The operation-related stiction is the result of over-range operation or capillary condensation after packaging resulting from operation in humid environment. We will present a survey and analysis of various release methods used to hedge stiction problems during fabrication, and then draw a useful comparison among various techniques. Likewise, we will examine some ideas put forward to remedy against post fabrication stiction. The underlying physics for stiction is fundamental to our understanding of the various forces coming into play on the structures in the dimensional scale most utilized in MEMS. We will have a brief look at the proposed theory for modeling these phenomena.
MEMS/MST technology was introduced over twenty years ago embellished by visions and promises of new products and applications that would revolutionize our lives. As a result we witnessed the creation of many new companies whose goal was to commercialize the technology. However, a few years later commercialization of the technology turned out to be an agonizingly process, a reaction attributed to the overestimation of the speed of technology transfer. This was further complicated by the fact that MEMS, while an enabling technology, is also a disruptive technology destined to completely replace existing, well proven familiar solutions. The adoption of new technology often requires marked evidence of superiority before displacing an established technology. As a rule of thumb, one needs to see a fivefold advantage in some parameters of importance, such as performance and cost, before there is any likelihood of adoption. Several MEMS devices have emerged that evolved into a significant commercial realization. Several others appear to be on the threshold of commercial success. The characteristics of some of these MEMS devices will be examined along with the major players and a number of issues related to overcoming the roadblocks of commercialization. We will also offer some predictions for the future of this technology.
A new algorithm, Square-and-Multiply for Modular Exponentiation (SMME), is proposed to calculate a modular exponentiation that is the core arithmetic function in RSA cryptography. The SMME scans the exponent form its MSB and pre-computes a set of exponents to the maximum bit length of l. These pre-computed exponents are stored in a look-up table. By using the look-up table, the number of multiplications required for modular exponentiation can be reduced. Modular multiplications are performed using a modified Montgomery's algorithm. The SMME takes in the order of n2(1 + 1(2l)) cycles to execute one n-bit modular exponentiation. The memory size to accommodate the pre- computed exponents is a 2l-1 (n + 1)-bit RAM. The SMME, with its regularity and local connections in a systolic array, makes it suitable for VLSI implementation. A 64-bit modular exponentiation chip is being designed using a 0.8 micrometers CMOS standard cell library from AMS. The simulation result show that at 25 MHz, the throughput is approximately 236 KBps; and an estimation of 40 KBps for a 512-bit exponent.
Silicon has been the leading material suited for the manufacture of a broad range of electronic, sensor, and actuator applications. However, it is limited in electronic device performance to temperatures below 250 degrees C and in mechanical device performance to below 600 degrees C. Its dim optical properties put silicon at a disadvantage with respect to the much acclaimed compound semiconductor rivals that have orders of magnitude higher optical emission. Consequently, for high-temperature MEMS applications, there is a need for semiconductors with good mechanical and thermal stability, and a wide bandgap for stable electronic and optoelectronic properties at elevated temperatures. This paper present a review of research activities on III-V nitrides and their experimentally established properties. We explore their suitability for microelectronics and microelectromechanical systems. Current efforts in developing III-N nitrides to extend the Si-based MEMS technology to applications in harsh environments is discussed. A summary is presented of the material properties that make them attractive for use in such environments. Challenges faced in crystal growth and development of processing techniques are also examined. Finally, a review is presented of the current state of novel optoelectronic devices made, and potential MEMS devices to be made from the proposed semiconductors, as well as an examination of issues facing future progress.
Integrated MEMS together with signal-conditioning electronics on the same chip appears to be the ultimate solution to realizing smart computer devices integratable into larger systems. This in principle will lead to systems with decentralized intelligence leading to applications in numerous fields. It is conceived that such devices would be the product of merging two mature technologies, that of microsensors and that of IC manufacture which is enjoying a well established success. Using common and suitable materials it is reasonable to expect a high degree of compatibility with little modification to standard processes. The various aspects of this co-integration will be analyzed and factors critical to the viability of the process, that go beyond mere technical feasibility will be highlighted. Australian research in this area is strong and continues to grow. We will pinpoint opportunities and constraints to the promising prospect of smart electronics and MEMS.
Silicidation of field emission tips brings about many improvements in device performance and long term reliability. Here we investigate the merits of titanium silicide coating as compared to other silicides including chromium. The silicidation takes place in two steps, deposition and high temperature alloying technique. Surface morphology was inspected and electrical characteristics were measured and compared with bare-silicon tips. The results show marked improvements in terms of lower turn-on voltage, enhanced emission, reduced current fluctuations, and homogeneous arrays. Moreover, titanium-silicide protected tips were harder, thermally stable, and discharge resistant.
In this paper, simulation of dynamic characteristics of pneumatically driven micropumps is presented. SPICE was used as a system level simulator. The SPICE model employed equivalent electrical circuit parameters extracted by an energy based calculation method. The thickness, side length of the diaphragm and forward resistance of valves were selected as variable to study the effect of design parameters in the performance of micropumps. Since the flow and pressure response of micropumps are similar to those of a differential electrical circuit, two parameters, namely, maximum amplitude and time constant of the system were used to discuss the simulation results. The results are of fundamental important to the understanding and optimization of the micropump.
Prompted by the successful experimental control of concavity of the field emitter profile, simulations on the effect of shape change and cone-side curvature on the field strength of the emitter were carried out. The dependency of field strength on the cone angle or the curvature angle is found to be approximately linear with 5.77 X 104 V/cm/degree. On the other hand, the dependency on the curvature angle (curvature radius) is approximately 4.98 X 104 V/cm/degree which is slightly lower than that of the straight cone angle variation but the average field intensity is about 1.6% higher than that of the pyramidal type. These results indicate that the cone-side curvature angle has a more pronounced effect on the strength of the electrical field than the cone angle. Hence a precise control of cone shape is an effective method of obtaining high electric fields. Optimal shapes of the field emitter can be achieved using appropriate anisotropic, followed by isotropic, etching techniques.