Kevin T. C. Chai

Bio: Kevin T. C. Chai is an academic researcher from Agency for Science, Technology and Research. The author has contributed to research in topics: CMOS & Computer science. The author has an hindex of 7, co-authored 28 publications receiving 349 citations.

The electronic stethoscope

Abstract: Most heart diseases are associated with and reflected by the sounds that the heart produces. Heart auscultation, defined as listening to the heart sound, has been a very important method for the early diagnosis of cardiac dysfunction. Traditional auscultation requires substantial clinical experience and good listening skills. The emergence of the electronic stethoscope has paved the way for a new field of computer-aided auscultation. This article provides an in-depth study of (1) the electronic stethoscope technology, and (2) the methodology for diagnosis of cardiac disorders based on computer-aided auscultation. The paper is based on a comprehensive review of (1) literature articles, (2) market (state-of-the-art) products, and (3) smartphone stethoscope apps. It covers in depth every key component of the computer-aided system with electronic stethoscope, from sensor design, front-end circuitry, denoising algorithm, heart sound segmentation, to the final machine learning techniques. Our intent is to provide an informative and illustrative presentation of the electronic stethoscope, which is valuable and beneficial to academics, researchers and engineers in the technical field, as well as to medical professionals to facilitate its use clinically. The paper provides the technological and medical basis for the development and commercialization of a real-time integrated heart sound detection, acquisition and quantification system.

Low-Cost, Tiny-Sized MEMS Hydrophone Sensor for Water Pipeline Leak Detection

Abstract: In this paper, we present an experimental investigation of a water pipeline leak detection system based on a low-cost, tiny-sized hydrophone sensor fabricated using the microelectromechanical system (MEMS) technologies. A 10 × 10 element arrayed MEMS hydrophone device with chip size of 3.5 × 3.5 mm $^2$ was used in the experiment. The hydrophone device is packaged with a customized on-board preamplification circuit using an acoustic transparent material. The overall package size of the MEMS hydrophone is $\Phi$ 1.2 × 2.5 cm. The packaged MEMS hydrophone achieves an acoustic sensitivity of −180 dB (re: 1 V/ $\mu$ Pa), a bandwidth from 10 Hz to 8 kHz, and a noise resolution of around 60 dB (re: 1 $\mu \text{Pa/}\sqrt{\text{Hz}}$ ) at 1 kHz. A section of ductile iron water pipeline with an internal diameter of 10 cm, wall thickness of 0.73 cm, and length of 30 m is constructed as the test bed for the water leak detection. Two different leak sizes with leak flow rates of about 30 and 180 L/min are designed along the pipe, which is pressurized at 3.2 bar. Analysis of the transient signals and spectrograms shows that the MEMS hydrophone can capture the key acoustic information of the water leak, i.e., identifying the leak and locating the leak position. The measurement results demonstrate the feasibility to construct an affordable, highly efficient, real-time, and permanent in-pipe pipeline health monitoring network based on the MEMS hydrophones due to their high performance, low cost, and tiny size.

Dual mode acoustic wave sensor for precise pressure reading

Abstract: In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm–50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of −50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellation which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications using the dual mode behavior of the sensor and differential readout at the same time.

AlN-on-SOI platform-based micro-machined hydrophone

Abstract: This paper reports a piezoelectric aluminum nitride (AlN) based micro-machined infrasonic hydrophone. We have conducted a systematic design study for the hydrophone sensor to meet the stringent requirements of underwater applications. The hydrophone sensor was fabricated on a cavity silicon-on-insulator (SOI) substrate using an in-house CMOS-compatible AlN-on-SOI process platform. A 5 × 5 arrayed hydrophone sensor was characterized thoroughly using an industry-standard hydrophone calibration instrument. The results show that the hydrophone achieved a sound sensitivity of −182.5 dB ± 0.3 dB (ref. to 1 V rms/μPa) and an eligible acceleration sensitivity of only −196.5 dB (ref. to 1 V rms/μg), respectively, a non-linearity of 0.11%, a noise resolution of 57.5 dB referenced to 1 μPa/√Hz within an ultra-low operation bandwidth of 10 Hz∼100 Hz, the highest noise resolution of micro-machined hydrophones reported to date, and better than traditional bulky hydrophones in terms of the same application. The size of the 5 × 5 arrayed hydrophone sensor is about 2 mm × 2 mm.

Medscape

Abstract: Secret History: Return of the Black Death Channel 4, 7-8pm In 1348 the Black Death swept through London, killing people within days of the appearance of their first symptoms. Exactly how many died, and why, has long been a mystery. This Secret History documentary follows experts as they pick through the evidence and reveal why the plague killed on such a scale. And they ask, what might be coming next?

Electrical biosensors and the label free detection of protein disease biomarkers

Abstract: Electrical detection methodologies are likely to underpin the progressive drive towards miniaturised, sensitive and portable biomarker detection protocols. In being easily integrated within standard electronic microfabrication formats, and developing capability in microfluidics, the facile multiplexed detection of a range of proteins in a small analytical volume becomes entirely feasible with something costing just a few thousand pounds and benchtop or handheld in scale. In this review, we focus on recent important advances in label free assays of protein using a number of electrical methods, including those based on electrochemical impedance spectroscopy (EIS), amperometry/voltammetry, potentiometry, conductometry and field-effect methods. We introduce their mechanistic features and examples of application and sensitivity. The current state of the art, real world applications and challenges are outlined.

A systematic survey of computer-aided diagnosis in medicine: Past and present developments

Abstract: Computer-aided diagnosis (CAD) in medicine is the result of a large amount of effort expended in the interface of medicine and computer science. As some CAD systems in medicine try to emulate the diagnostic decision-making process of medical experts, they can be considered as expert systems in medicine. Furthermore, CAD systems in medicine may process clinical data that can be complex and/or massive in size. They do so in order to infer new knowledge from data and use that knowledge to improve their diagnostic performance over time. Therefore, such systems can also be viewed as intelligent systems because they use a feedback mechanism to improve their performance over time. The main aim of the literature survey described in this paper is to provide a comprehensive overview of past and current CAD developments. This survey/review can be of significant value to researchers and professionals in medicine and computer science. There are already some reviews about specific aspects of CAD in medicine. However, this paper focuses on the entire spectrum of the capabilities of CAD systems in medicine. It also identifies the key developments that have led to today's state-of-the-art in this area. It presents an extensive and systematic literature review of CAD in medicine, based on 251 carefully selected publications. While medicine and computer science have advanced dramatically in recent years, each area has also become profoundly more complex. This paper advocates that in order to further develop and improve CAD, it is required to have well-coordinated work among researchers and professionals in these two constituent fields. Finally, this survey helps to highlight areas where there are opportunities to make significant new contributions. This may profoundly impact future research in medicine and in select areas of computer science.