Alex Hariz

Applications of modern sensors and wireless technology in effective wound management

The management of chronic wounds has emerged as a major health care challenge during the 21st century consuming, significant portions of health care budgets. Chronic wounds such as diabetic foot ulcers, leg ulcers, and pressure sores have a significant negative impact on the quality of life of affected individuals. Covering wounds with suitable dressings facilitates the healing process and is common practice in wound management plans. However, standard dressings do not provide insights into the status of the wound underneath. Parameters such as moisture, pressure, temperature and pH inside the dressings are indicative of the healing rate, infection, and wound healing phase. But owing to the lack of information available from within the dressings, these are often changed to inspect the wound, disturbing the normal healing process of wounds in addition to causing pain to the patient. Sensors embedded in the dressing would provide clinicians and nurses with important information that would aid in wound care decision making, improve patient comfort, and reduce the frequency of dressing changes. The potential benefits of this enabling technology would be seen in terms of a reduction in hospitalization time and health care cost. Modern sensing technology along with wireless radio frequency communication technology is poised to make significant advances in wound management. This review discusses issues related to the design and implementation of sensor technology and telemetry systems both incorporated in wound dressings to devise an automated wound monitoring technology, and also surveys the literature available on current sensor and wireless telemetry systems.

An Improved Flexible Telemetry System to Autonomously Monitor Sub-Bandage Pressure and Wound Moisture

This paper presents the development of an improved mobile-based telemetric dual mode sensing system to monitor pressure and moisture levels in compression bandages and dressings used for chronic wound management. The system is fabricated on a 0.2 mm thick flexible printed circuit material, and is capable of sensing pressure and moisture at two locations simultaneously within a compression bandage and wound dressing. The sensors are calibrated to sense both parameters accurately, and the data are then transmitted wirelessly to a receiver connected to a mobile device. An error-correction algorithm is developed to compensate the degradation in measurement quality due to battery power drop over time. An Android application is also implemented to automatically receive, process, and display the sensed wound parameters. The performance of the sensing system is first validated on a mannequin limb using a compression bandage and wound dressings, and then tested on a healthy volunteer to acquire real-time performance parameters. The results obtained here suggest that this dual mode sensor can perform reliably when placed on a human limb.

Wide-bandgap materials for novel electronic devices and MEMS

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.

Perspectives on organolead halide perovskite photovoltaics

Abstract. 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.

Carbon nanotubes on polymer-based pressure micro-sensor for manometric catheters

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.

Deformable grating light modulator array for use as wavelength-selective switch

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 simulations.

Micro engineering-a brief overview

We report on the emerging field of microengineering. This novel technology involves the miniaturization of mechanics. Just as miniaturization of electronics has resulted in revolutionary advances, microengineering is poised to produce a revolution of its own. Furthermore, microengineering is based on the technology of microelectronics utilizing the same processes, equipment, and skills. It also requires further advances in specific areas. The aim of microengineering is to manufacture fully assembled electromechanical devices and systems at the micron scale to perform functions efficiently, conveniently, and not otherwise possible with their large-scale counterparts. With a suitable choice of materials, electronics can be integrated within, resulting in systems with decentralized intelligence. Microengineering holds a potential for impact in fields as diverse as automechanics, medicine, information storage and retrieval, fiberoptic communications, and unmanned space exploration.<<ETX>>

Flexible Pressure Sensor on Polymeric Materials

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.

A new disposable MEMS-based manometric catheter for in-vivo medical tests

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.

A simulation of the structural stability of field emission micro-tips against discharge

The stability of the field emitter against discharge was investigated by examining the field distribution around the emitter. For the study, simulations of the field distribution were carried out by varying the tip height and gate geometry. The results indicate, that for geometries with extrusion of the gate electrode from the dielectric, there appears another strong field concentration point along the lower edge of the gate electrode. The intensity initially increases with increasing extrusion length and then saturates. The existence of a counter electrode within the device structure indicates that the device is prone to discharge during operation. This possibility is the strongest when the device has a smaller tip height and a larger cone half angle. It is concluded that, by designing the device with a larger tip height and a smaller cone angle, the device will have a more stable operation.