This paper presents a microcontroller-based solution to classify blood glucose levels using acetone and ethanol breath volatile organic compounds. Two metal oxide semiconductor-based chemical sensors able to detect acetone and ethanol at parts per million concentrations were used. The sensors were tested in a controlled setup with humidified air spiked with acetone and ethanol, mimicking human breath corresponding to low and high blood glucose groups. A support vector machine algorithm was trained and implemented in a microcontroller. In a real time-time test, the trained algorithm classified low and high blood glucose groups with 97% accuracy. Subsequently, a smart wristband prototype that integrates the two sensors was developed. An Arduino-based wearable microcontroller platform was used for its small formfactor and a low-power operation. The wristband is enclosed in a 3D printed housing and powered by an onboard 3.7 V 500 mAh rechargeable Li-ion battery. A smartphone app communicates with the wristband through Bluetooth, allows data visualization, and saves data in the cloud. The presented work makes a significant contribution towards the development of a wearable device for detecting blood glucose levels from a patient’s breath.
Our ambient air carries hundreds of volatile organic compounds that can provide information about the toxicity and hygiene of our immediate environment. This paper presents prototype electronic nose designs that integrate array of chemical sensors into the embedded system to detect volatile organic compounds in the ambient air. Two specific applications for the electronic nose of detecting food spoilage and identifying sources of indoor air pollutants are discussed. A system with three chemical sensors was tested with various food items at varying stages of spoilage. The presented results show that food spoilage can be detected with a high degree of accuracy. A second system with eleven sensors was tested with various household items that emit compounds known to have adverse effects to human health. The results show that with the considered sensor array, the tested sources can be identified with a high degree of accuracy. The presented designs are being further improved to achieve a higher accuracy, further expand the compounds that can be identified for a broader range of applications, and to build a miniaturized hand-held electronic nose device. The system development, testing methodologies, and results analysis are presented and discussed.
A temperature-stable, low-power ring oscillator design with a wide tuning frequency range, for implementation in an
ASIC is presented. The design uses a new arrangement of chain delay elements consisting of a current-starved inverter
and a CMOS capacitor. The delay is controlled by changing the current through the delay elements. The simulation
results show that the frequency of the presented oscillator is stable against ambient temperature variations, with less than
0.5% deviation in frequency when the temperature was changed from 0 to 50°C. The oscillation frequency is highly
sensitive to the control voltage (sensitivity ~10 mV) with a tuning range of 203 MHz for 0.9 V increase in the input
voltage, and simulated power consumption of 1.2 nW. The design and simulation results of the ring oscillator with 180
nm technology are presented and discussed. The presented design is applicable in advanced sensing systems, including
biomedical, chemical, and other sensors.
A polymer pellet-based sensor device comprised of polypyrrole (PPy), polymethyl methacrylate (PMMA) and
polyethylene glycol (PEG), its fabrication methods, and the experimental results for low-concentration acetone detection
are presented. The design consists of a double layer pellet, where the top layer consists of PPy/PMMA and the bottom
layer is composed of PPy/PMMA/PEG. Both sets of material compositions are synthesized by readily realizable
chemical polymerization techniques. The mechanism of the sensor operation is based on the change in resistance of PPy
and the swelling of PMMA when exposed to acetone, thereby changing the resistance of the layers. The resistances
measured on the two layers, and across the pellet, are taken as the three output signals of the sensor. Because the
PPy/PMMA and PPy/PMMA/PEG layers respond differently to acetone, as well as to other volatile organic compounds,
it is demonstrated that the three output signals can allow the presented sensor to have a better sensitivity and selectivity
than previously reported devices. Materials characterizations show formation of new composite with PPy/PMMA/PEG.
Material response at various concentrations of acetone was conducted using quartz crystal microbalance (QCM). It was
observed that the frequency decreased by 98 Hz for 290 ppm of acetone and by 411 Hz for 1160 ppm. Experimental
results with a double layer pellet of PPy/PMMA and PPy/PMMA/PEG show an improved selectivity of acetone over
ethanol. The reported acetone sensor is applicable for biomedical and other applications.
A chipless sensor tag-based radio frequency identification (RFID) technology that allows wireless collection of
information from the environment, and the monitoring and accessing of the given information through cyberspace is
presented. The developed system consists of a cyber enabled RFID reader and passive chipless RFID sensor tags. The
reader is comprised of an analog part that wirelessly communicates with the sensor tags, and a single board computer
(SBC) part. Each passive chipless sensor tag consists of a microstrip antenna and a sensor. The sensor information is
amplitude modulated in the backscattered signal of the tag. The analog reader part receives the backscattered signal and
feeds it to the SBC, which computes the sensor information into a 96 bit serialized global trade item number (SGTIN-96)
electronic product code (EPC). Moreover, the SBC makes the information available on a cyberspace-accessible secure
user interface. The reported system has been applied for temperature sensing, where the change in temperature at the tag
ranging from 27°C to 140°C resulted in a 28% amplitude change at the analog part of the reader. The temperature at the
tag has been monitored by accessing the reader through cyberspace using a web-based user interfaces developed for the
SBC.
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