Wearable RF sensors for non-invasive detection of blood-glucose levels

PhDRadio frequency (RF) techniques have the potential to provide blood glucose readings through sensing the glucose dependent change in dielectric properties of the biological tissue. Such technique can enable much desired non-invasive and continuous monitoring of blood glucose level. In this work, we present realistic glucose dependence of dielectric properties as well as basic understanding of resonator behaviour while radiating towards the lossy biological tissue. To investigate the potential of RF techniques, two resonators, operating at microwave frequencies when placed radiating towards the biological tissue, are designed and fabricated. The spiral resonator is tested with liquid and semi-solid phantoms containing different amounts of sugar. An analytical formulation to retrieve the dielectric properties of the biological tissues is improved. In order to perform realistic tests, novel tissue mimicking materials for an extremely wide frequency range are proposed. Glucose dependance of the blood mimicking material dielectric properties are further investigated by adding realistic glucose amounts to the blood mimicking material and dielectric spectroscopy is performed. Next, a single pole Cole-Cole model is fitted to the median of the dielectric property measurements. In addition, a patch resonator is simulated with four-layered digital phantom and tested with the four-layered physical tissue mimicking phantom. Finally, a double parameter measurement platform is constructed by combining the patch resonator and a commercial force sensor to perform controlled experiments with humans. Also, the force dependant response of the patch resonator is quantified. Soda tests is performed on five subjects with the platform, all subjects were asked to apply the same level of force. Spiral resonator is also applied to examine the glucose changes of two human subjects during the soda test. The results suggests that, although the glucose-dependance of the dielectric properties is relatively small, the input impedance of a microwave resonator is still sensitive to such small alterations

Non-Invasive Blood Glucose Monitoring Using Electromagnetic Sensors

Monitoring glycemia levels in people with diabetes has developed rapidly over the last decade. A broad range of easy-to-use systems of reliable accuracies are now deployed in the market following the introduction of the invasive self-monitoring blood glucose meters (i.e., Glucometers) that utilize the capillary blood samples from the fingertips of diabetic patients. Besides, semi-invasive continuous monitors (CGM) are currently being used to quantify the glucose analyte in interstitial fluids (ISF) using an implantable needle-like electrochemical sensors. However, the limitations and discomforts associated with these finger-pricking and implantable point-of-care devices have established a new demand for complete non-invasive pain-free and low-cost blood glucose monitors to allow for more frequent and convenient glucose checks and thereby contribute more generously to diabetes care and prevention. Towards that goal, researchers have been developing alternative techniques that are more convenient, affordable, pain-free, and can be used for continuous non-invasive blood glucose monitoring. In this research, a variety of electromagnetic sensing techniques were developed for reliably monitoring the blood glucose levels of clinical relevance to diabetes using the non-ionizing electromagnetic radiations of no hazards when penetrating the body. The sensing structures and devices introduced in this study were designed to operate in specific frequency spectrums that promise a reliable and sensitive glucose detection from centimeter- to millimeter-wave bands. Particularly, three different technologies were proposed and investigated at the Centre for Intelligent Antenna and Radio Systems (CIARS): Complementary Split-Ring Resonators (CSRRs), Whispering Gallery Modes (WGMs) sensors, and Frequency-Modulated Continuous-Wave (FMCW) millimeter-Wave Radars. Multiple sensing devices were developed using those proposed technologies in the micro/millimeter-wave spectrums of interest. A comprehensive study was conducted for the functionality, sensitivity, and repeatability analysis of each sensing device. Particularly, the sensors were thoroughly designed, optimized, fabricated, and practically tested in the laboratory with the desired glucose sensitivity performance. Different topologies and configurations of the proposed sensors were studied and compared in sensitivity using experimental and numerical analysis tools. Besides, machine learning and signal processing tools were intelligently applied to analyze the frequency responses of the sensors and reliably identify different glucose levels. The developed glucose sensors were coupled with frequency-compatible radar boards to realize small mobile glucose sensing systems of reduced cost. The proposed sensors, beside their impressive detection capability of the diabetes-spectrum glucose concentrations, are endowed with favourable advantages of simple fabrication, low-power consumption, miniaturized compact sizing, non-ionizing radiation, and minimum health risk or impact for human beings. Such attractive features promote the proposed sensors as possible candidates for development as mobile, portable/wearable gadgets for affordable non-invasive blood glucose monitoring for diabetes. The introduced sensing structures could also be employed for other vital sensing applications such as liquid type/quantity identification, oil adulteration detection, milk quality control, and virus/bacteria detection. Another focus of this thesis is to investigate the electromagnetic behavior of the glucose in blood mimicking tissues across the microwave spectrum from 200 MHz to 67 GHz using a commercial characterization system (DAK-TL) developed by SPEAG. This is beneficial to locate the promising frequency spectrums that are most responsive to slight variations in glucose concentrations, and to identify the amount of change in the dielectric properties due to different concentrations of interest. Besides, the effect of the blood typing and medication was also investigated by measuring the dielectric properties of synthetic “artificial” as well as authentic “human” blood samples of different ABO-Rh types and with different medications. Measured results have posed for other factors that may impact the developed microwave sensors accuracy and sensitivity including the patient’s blood type, pre-existing medical conditions, or other illnesses

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 11)

This continuing bibliography lists index for 3256 patents and patent applications introduced into the NASA scientific and technical informations system from January 1977 through June 1977. The index section contains fix indexes: subject, inventor, source, number, and accession number

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Reusable Reentry Satellite (RRS) system design study

The Reusable Reentry Satellite (RRS) is intended to provide investigators in several biological disciplines with a relatively inexpensive method to access space for up to 60 days with eventual recovery on Earth. The RRS will permit totally intact, relatively soft, recovery of the vehicle, system refurbishment, and reflight with new and varied payloads. The RRS is to be capable of three reflights per year over a 10-year program lifetime. The RRS vehicle will have a large and readily accessible volume near the vehicle center of gravity for the Payload Module (PM) containing the experiment hardware. The vehicle is configured to permit the experimenter late access to the PM prior to launch and rapid access following recovery. The RRS will operate in one of two modes: (1) as a free-flying spacecraft in orbit, and will be allowed to drift in attitude to provide an acceleration environment of less than 10(exp -5) g. the acceleration environment during orbital trim maneuvers will be less than 10(exp -3) g; and (2) as an artificial gravity system which spins at controlled rates to provide an artificial gravity of up to 1.5 Earth g. The RRS system will be designed to be rugged, easily maintained, and economically refurbishable for the next flight. Some systems may be designed to be replaced rather than refurbished, if cost effective and capable of meeting the specified turnaround time. The minimum time between recovery and reflight will be approximately 60 days. The PMs will be designed to be relatively autonomous, with experiments that require few commands and limited telemetry. Mass data storage will be accommodated in the PM. The hardware development and implementation phase is currently expected to start in 1991 with a first launch in late 1993

Investigations of water-based liquid antennas for wireless communications

Water-based liquid antennas are a new type of antennas, which have attracted increasing attention in recent years. They have emerged as promising alternatives to traditional antennas for many applications. The purpose of this thesis is to present a comprehensive study into water-based liquid antennas, aiming at gaining a better understanding of water-based liquid antennas from the liquids used to the antenna designs. This thesis is comprised of two main research areas. The first area under investigation focuses on water-based liquid property characterisation. In water-based liquid antenna designs, a precise knowledge of the complex permittivity of the liquid is essential. Three water-based liquids, namely pure water, water with propylene glycol (PG) and salty water, are carefully studied from an antenna design point of view. A liquid measurement software package is developed to automatically record the liquid complex permittivity data under different temperatures, and measurements are conducted. The experimental data are processed to obtain accurate mathematical expressions for the complex permittivity of these liquids over a temperature range 0 ~ 70oC (for pure water and salty water) and -10oC ~ 70oC (for water with PG), frequency range 0 ~ 18 GHz, PG concentration 0 ~ 70% and salinity 0.1 ~ 50 ppt. Water with PG is proposed as an alternative candidate for pure water in cold climates. It is demonstrated that the performance of the antenna will not be changed significantly by using water with PG. The second area concerns water-based liquid antenna designs and is divided into three sections: The first section deals with the water antenna working as a conducting antenna. A water monopole antenna with a dielectric layer is designed. Salty water is used to replace the conducting material (usually copper) in traditional designs. A comprehensive parametric study is performed and the physical insights behind the design are studied. A close relationship between the salty water conductivity and antenna radiation efficiency is explored. The second section investigates the hybrid water antenna for hand-portable applications. By combining the resonance from the water dielectric resonator antenna (DRA) and that from the feeding structure, a wideband response can be achieved. Three hybrid water antennas are developed with low profiles and high efficiency. The unique features of water, namely liquidity and transparency are effectively utilised. A complex feeding structure is placed inside the water dielectric resonator (DR) to feed the water DR and also work as a radiating element. The third section relates to the water loaded reconfigurable antennas. Two water loaded reconfigurable antennas with special 3D folded structures are designed. Different technologies are applied in the reconfigurable designs such as the special folded 3D monopole structure, the use of water and its holder as a transparent dielectric loading, and the integration of an active component. The results show that the designs have compact sizes, reasonable efficiency and bandwidths. This thesis has successfully demonstrated the attractive features and great potential of water-based liquid antennas. The knowledge gained in this work is very valuable for future water-based liquid antenna development

Cumulative index to NASA Tech Briefs, 1970-1975

Tech briefs of technology derived from the research and development activities of the National Aeronautics and Space Administration are presented. Abstracts and indexes of subject, personal author, originating center, and tech brief number for the 1970-1975 tech briefs are presented

Index to NASA Tech Briefs, 1972

Abstracts of 1972 NASA Tech Briefs are presented. Four indexes are included: subject, personal author, originating center, and Tech Brief number

An implantable encased microstrip ring disk antenna

In this paper the performance of an implantable encased miniature microstrip ring disk antenna is investigated for wireless biomedical applications. It is shown that the encased antenna designed to operate in free space will exhibit a significant shift in the resonant frequency when implanted in a tissue mimicking gel. By modifying the relative dielectric constant of the material and the length of the microstrip annular ring, the implanted encased microstrip ring disk antenna exhibits acceptable results for the magnitude of the reflection coefficient and the maximum gain at 2.4 GHz

Structural, Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Nanocrystalline Materials: Synthesis, Characterization and Application

This book is a collection of the research articles and review article, published in special issue "Structural, Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Nanocrystalline Materials: Synthesis, Characterization and Application"