PHOTONICALLY SINTERED PZT ENERGY HARVESTER

ABSTRACT This paper reports an Aerosol-Jet printed micro scale Lead Zirconate Titanate (PZT) energy harvester directly sintered on a low melting point substrate in less than 1 msec using photonic sintering technology. To improve the output signal, d33 piezoelectric mode was employed by patterning silver electrodes as an interdigitated structure on top of a PZT film. The size of the device is 15.5 mm × 13.5 mm × 0.2 mm. Up to 2.4 V was measured at 145 MPa tensile bending stress level in the device after poling at 180 °C for 2 hours with an electric field of 30 kV/cm. Using an oscillating stress (~2.5 Hz) of approximately 145 MPa, the power as a function of load was determined by connecting the device with various series resistive loads. A maximal power of 0.1 μW was generated when driving into a 10 MΩ load. A PZT energy harvester, for the first time, is demonstrated which has been directly printed and sintered on a low melting temperature flexible substrate without a film transfer processes. This not only dramatically simplifies the fabrication process, but expands the possible substrate materials for PZT energy harvesters

Low-Power Wearable ECG Monitoring System for Multiple-Patient Remote Monitoring

Many devices and solutions for remote electrocardiogram (ECG) monitoring have been proposed in the literature. These solutions typically have a large marginal cost per added sensor and are not seamlessly integrated with other smart home solutions. Here, we propose an ECG remote monitoring system that is dedicated to non-technical users in need of long-term health monitoring in residential environments and is integrated in a broader Internet-of-Things (IoT) infrastructure. Our prototype consists of a complete vertical solution with a series of advantages with respect to the state of the art, considering both the prototypes with integrated front end and prototypes realized with off-the-shelf components: 1) ECG prototype sensors with record-low energy per effective number of quantized levels; 2) an architecture providing low marginal cost per added sensor/user; and 3) the possibility of seamless integration with other smart home systems through a single IoT infrastructure

Cross-instrument feasibility, validity, and reproducibility of wireless heart rate monitors:Novel opportunities for extended daily life monitoring

Wired ambulatory monitoring of the electrocardiogram (ECG) is an established method used by researchers and clinicians. Recently, a new generation of wireless, compact, and relatively inexpensive heart rate monitors have become available. However, before these monitors can be used in scientific research and clinical practice, their feasibility, validity, and reproducibility characteristics have to be investigated. Therefore, we tested how two wireless heart rate monitors (i.e., the Ithlete photoplethysmography (PPG) finger sensor and the Cortrium C3 ECG monitor perform against an established wired reference method (the VU-AMS ambulatory ECG monitor). Monitors were tested on cross-instrument and test-retest reproducibility in a controlled laboratory setting, while feasibility was evaluated in protocolled ambulatory settings at home. We found that the Cortrium and the Ithlete monitors showed acceptable agreement with the VU-AMS reference in laboratory setting. In ambulatory settings, assessments were feasible with both wireless devices although more valid data were obtained with the Cortrium than with the Ithlete. We conclude that both monitors have their merits under controlled laboratory settings where motion artefacts are minimized and stationarity of the ECG signal is optimized by design. These findings are promising for long-term ambulatory ECG measurements, although more research is needed to test whether the wireless devices' feasibility, validity, and reproducibility characteristics also hold in unprotocolled daily life settings with natural variations in posture and activities

Synchronization and Analysis of Multimodal Medical Data

The United States suffers from a significant disparity in the availability of the medical resources and expertise among different regions of the country. Patients in rural areas may not have the opportunity to consult with a physician until their disease progresses to later stages, resulting in a considerable decrease in quality of life. Advances in telemedicine systems that can provide remote communication, medical data acquisition, and medical data analysis promise a significant improvement to early access to medical care and diagnoses for disadvantaged individuals. In this thesis, we make several contributions on topics that contribute to the improvement of telemedicine systems. First, we propose several synchronization approaches for the acquisition of multimodal medical data. Second, we explore several machine learning techniques that analyze cardiovascular data and provide feedback about the patient\u27s health to the physician. We found that the Random Forest algorithm was the most accurate in predicting heart disease in a patient

Capsule endoscopy system with novel imaging algorithms

Wireless capsule endoscopy (WCE) is a state-of-the-art technology to receive images of human intestine for medical diagnostics. In WCE, the patient ingests a specially designed electronic capsule which has imaging and wireless transmission capabilities inside it. While the capsule travels through the gastrointestinal (GI) tract, it captures images and sends them wirelessly to an outside data logger unit. The data logger stores the image data and then they are transferred to a personal computer (PC) where the images are reconstructed and displayed for diagnosis. The key design challenge in WCE is to reduce the area and power consumption of the capsule while maintaining acceptable image reconstruction. In this research, the unique properties of WCE images are identified by analyzing hundreds of endoscopic images and video frames, and then these properties are used to develop novel and low complexity compression algorithms tailored for capsule endoscopy. The proposed image compressor consists of a new YEF color space converter, lossless prediction coder, customizable chrominance sub-sampler and an efficient Golomb-Rice encoder. The scheme has both lossy and lossless modes and is further customized to work with two lighting modes – conventional white light imaging (WLI) and emerging narrow band imaging (NBI). The average compression ratio achieved using the proposed lossy compression algorithm is 80.4% for WBI and 79.2% for NBI with high reconstruction quality index for both bands. Two surveys have been conducted which show that the reconstructed images have high acceptability among medical imaging doctors and gastroenterologists. The imaging algorithms have been realized in hardware description language (HDL) and their functionalities have been verified in field programmable gate array (FPGA) board. Later it was implemented in a 0.18 μm complementary metal oxide semiconductor (CMOS) technology and the chip was fabricated. Due to the low complexity of the core compressor, it consumes only 43 µW of power and 0.032 mm2 of area. The compressor is designed to work with commercial low-power image sensor that outputs image pixels in raster scan fashion, eliminating the need of significant input buffer memory. To demonstrate the advantage, a prototype of the complete WCE system including an FPGA based electronic capsule, a microcontroller based data logger unit and a Windows based image reconstruction software have been developed. The capsule contains the proposed low complexity image compressor and can generate both lossy and lossless compressed bit-stream. The capsule prototype also supports both white light imaging (WLI) and narrow band imaging (NBI) imaging modes and communicates with the data logger in full duplex fashion, which enables configuring the image size and imaging mode in real time during the examination. The developed data logger is portable and has a high data rate wireless connectivity including Bluetooth, graphical display for real time image viewing with state-of-the-art touch screen technology. The data are logged in micro SD cards and can be transferred to PC or Smartphone using card reader, USB interface, or Bluetooth wireless link. The workstation software can decompress and show the reconstructed images. The images can be navigated, marked, zoomed and can be played as video. Finally, ex-vivo testing of the WCE system has been done in pig's intestine to validate its performance

Enhanced Piezoelectric Performance of Printed PZT Films on Low Temperature Substrates

Since piezoelectric effect was discovered in 1880, it has been widely used in micro-actuators, sensors, and energy harvesters. Lead Zirconate Titanate (PZT) is a commonly used piezoelectric material due to the high piezoelectric response. The basic PZT film fabrication process includes deposition, sintering, and poling. However, due to the high sintering temperature (\u3e 800 °C) of PZT, only high melting point material can be served as the substrate. Otherwise, complex film transfer approach is needed to achieve flexible and foldable PZT devices. The exploration is accordingly necessary to realize direct fabrication of PZT films on low melting point substrates without affecting the piezoelectric performance. In order to lower the PZT film sintering temperature, in this work, the effect of the powder size and sintering aid on the sintering temperature was studied. A maskless, CAD driven, non-contact direct printing system, aerosol jet printer, was used to deposit PZT thick films on the substrate. This technique allows creating features without masking and etching processes that are generally required for realizing designed features via conventional deposition approaches. Broadband, sub-millisecond, high intensity flash pulses were used to sinter the PZT films. The role of all sintering parameters was investigated to regulate the sintering quality of the PZT thick films. The photonically sintered films showed much lower substrate temperature increase mainly due to the extremely short pulse duration and temperature gradient through the film thickness. The superior piezoelectric property to thermally sintered group was also obtained. This process significantly shortens the processing duration and dramatically expands the possible substrate materials. It accordingly opens the possibility of processing PZT film directly on low melting point materials. A PZT energy harvester based on this process was directly fabricated on the polyethylene terephthalate (PET) substrate to demonstrate the capability. The relation between the load and the generated power was investigated to obtain the highest output power. Up to 0.1 μW was generated from this flexible energy harvester when connected with 10 MΩ resistive load. Photonic sintering of PZT film also creates the opportunity of processing poling during sintering. Different combinations of the sintering and poling techniques were studied. It was observed that the best piezoelectric property was obtained while performing poling during photonic sintering. Consequently, a new method of printing, sintering, and poling of micro-scaled PZT films was demonstrated in this work resulting in high performance films. This process provides the capability of realizing PZT devices on low temperature substrate, facilitates the fabrication of flexible piezoelectric devices, and enhances the piezoelectric property

Extracting clinically-actionable information from wearable physiological monitors

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 161-167).In this thesis I examine several ways of extracting information from wearable monitors so as to help make clinical decisions. Wearable physiological sensors are developing rapidly, and pose a possible part of the solution to the demands of an aging population and rising health care costs. It is important that the data produced by such sensors be processed into information that is clinically relevant and will have an impact on the practice of medicine. I collected data in an ambulatory setting from several wearable physiological sensors, including electrocardiogram, arterial blood pressure, pulse plethysmograph, respiration and acceleration. Using this data set, I demonstrated a few approaches - including signal processing, and algorithms based on the application of physiological models - to extract clinically relevant information. These approaches are potentially of interest to both device makers interested in developing wearable monitors, and to clinicians who will be using such monitors in the future.by Bryan Haslam.S.M

Ultra-low-power circuits and systems for wearable and implantable medical devices

Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 219-231).Advances in circuits, sensors, and energy storage elements have opened up many new possibilities in the health industry. In the area of wearable devices, the miniaturization of electronics has spurred the rapid development of wearable vital signs, activity, and fitness monitors. Maximizing the time between battery recharge places stringent requirements on power consumption by the device. For implantable devices, the situation is exacerbated by the fact that energy storage capacity is limited by volume constraints, and frequent battery replacement via surgery is undesirable. In this case, the design of energy-efficient circuits and systems becomes even more crucial. This thesis explores the design of energy-efficient circuits and systems for two medical applications. The first half of the thesis focuses on the design and implementation of an ultra-low-power, mixed-signal front-end for a wearable ECG monitor in a 0.18pm CMOS process. A mixed-signal architecture together with analog circuit optimizations enable ultra-low-voltage operation at 0.6V which provides power savings through voltage scaling, and ensures compatibility with state-of-the-art DSPs. The fully-integrated front-end consumes just 2.9[mu]W, which is two orders of magnitude lower than commercially available parts. The second half of this thesis focuses on ultra-low-power system design and energy-efficient neural stimulation for a proof-of-concept fully-implantable cochlear implant. First, implantable acoustic sensing is demonstrated by sensing the motion of a human cadaveric middle ear with a piezoelectric sensor. Second, alternate energy-efficient electrical stimulation waveforms are investigated to reduce neural stimulation power when compared to the conventional rectangular waveform. The energy-optimal waveform is analyzed using a computational nerve fiber model, and validated with in-vivo ECAP recordings in the auditory nerve of two cats and with psychophysical tests in two human cochlear implant users. Preliminary human subject testing shows that charge and energy savings of 20-30% and 15-35% respectively are possible with alternative waveforms. A system-on-chip comprising the sensor interface, reconfigurable sound processor, and arbitrary-waveform neural stimulator is implemented in a 0.18[mu]m high-voltage CMOS process to demonstrate the feasibility of this system. The sensor interface and sound processor consume just 12[mu]W of power, representing just 2% of the overall system power which is dominated by stimulation. As a result, the energy savings from using alternative stimulation waveforms transfer directly to the system.by Marcus Yip.Ph.D