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Description
There is a tremendous need for wireless biological signals acquisition for the microelectrode-based neural interface to reduce the mechanical impacts introduced by wire-interconnects system. Long wire connections impede the ability to continuously record the neural signal for chronic application from the rodent's brain. Furthermore, connecting and/or disconnecting Omnetics interconnects often introduces mechanical stress which causes blood vessel to rupture and leads to trauma to the brain tissue. Following the initial implantation trauma, glial tissue formation around the microelectrode and may possibly lead to the microelectrode signal degradation. The aim of this project is to design, develop, and test a compact and power efficient integrated system (IS) that is able to (a) wirelessly transmit triggering signal from the computer to the signal generator which supplies voltage waveforms that move the MEMS microelectrodes, (b) wirelessly transmit neural data from the brain to the external computer, and (c) provide an electrical interface for a closed loop control to continuously move the microelectrode till a proper quality of neural signal is achieved. One of the main challenges of this project is the limited data transmission rate of the commercially available wireless system to transmit 400 kbps of digitized neural signals/electrode, which include spikes, local field potential (LFP), and noise. A commercially available Bluetooth module is only capable to transmit at a total of 115 kbps data transfer rate. The approach to this challenge is to digitize the analog neural signal with a lower accuracy ADC to lower the data rate, so that is reasonable to wirelessly transfer neural data of one channel. In addition, due to the limited space and weight bearing capability to the rodent's head, a compact and power efficient integrated system is needed to reduce the packaged volume and power consumption. 3D SoP technology has been used to stack the PCBs in a 3D form-factor, proper routing designs and techniques are implemented to reduce the electrical routing resistances and the parasitic RC delay. It is expected that this 3D design will reduce the power consumption significantly in comparison to the 2D one. The progress of this project is divided into three different phases, which can be outlined as follow: a) Design, develop, and test Bluetooth wireless system to transmit the triggering signal from the computer to the signal generator. The system is designed for three moveable microelectrodes. b) Design, develop, and test Bluetooth wireless system to wirelessly transmit an amplified (200 gain) neural signal from one single electrode to an external computer. c) Design, develop, and test a closed loop control system that continuously moves a microelectrode in searching of an acceptable quality of neural spikes. The outcome of this project can be used not only for the need of neural application but also for a wider and general applications that requires customized signal generations and wireless data transmission.
ContributorsZhou, Li (Author) / Muthuswamy, Jitendran (Thesis advisor) / Sutanto, Jemmy (Thesis advisor) / Yu, Hongyu (Committee member) / Arizona State University (Publisher)
Created2012
Description
Demand for biosensor research applications is growing steadily. According to a new report by Frost & Sullivan, the biosensor market is expected to reach $14.42 billion by 2016. Clinical diagnostic applications continue to be the largest market for biosensors, and this demand is likely to continue through 2016 and beyond. Biosensor technology for use in clinical diagnostics, however, requires translational research that moves bench science and theoretical knowledge toward marketable products. Despite the high volume of academic research to date, only a handful of biomedical devices have become viable commercial applications. Academic research must increase its focus on practical uses for biosensors. This dissertation is an example of this increased focus, and discusses work to advance microfluidic-based protein biosensor technologies for practical use in clinical diagnostics. Four areas of work are discussed: The first involved work to develop reusable/reconfigurable biosensors that are useful in applications like biochemical science and analytical chemistry that require detailed sensor calibration. This work resulted in a prototype sensor and an in-situ electrochemical surface regeneration technique that can be used to produce microfluidic-based reusable biosensors. The second area of work looked at non-specific adsorption (NSA) of biomolecules, which is a persistent challenge in conventional microfluidic biosensors. The results of this work produced design methods that reduce the NSA. The third area of work involved a novel microfluidic sensing platform that was designed to detect target biomarkers using competitive protein adsorption. This technique uses physical adsorption of proteins to a surface rather than complex and time-consuming immobilization procedures. This method enabled us to selectively detect a thyroid cancer biomarker, thyroglobulin, in a controlled-proteins cocktail and a cardiovascular biomarker, fibrinogen, in undiluted human serum. The fourth area of work involved expanding the technique to produce a unique protein identification method; Pattern-recognition. A sample mixture of proteins generates a distinctive composite pattern upon interaction with a sensing platform consisting of multiple surfaces whereby each surface consists of a distinct type of protein pre-adsorbed on the surface. The utility of the "pattern-recognition" sensing mechanism was then verified via recognition of a particular biomarker, C-reactive protein, in the cocktail sample mixture.
ContributorsChoi, Seokheun (Author) / Chae, Junseok (Thesis advisor) / Tao, Nongjian (Committee member) / Yu, Hongyu (Committee member) / Forzani, Erica (Committee member) / Arizona State University (Publisher)
Created2011
Description
The past two decades have been monumental in the advancement of microchips designed for a diverse range of medical applications and bio-analysis. Owing to the remarkable progress in micro-fabrication technology, complex chemical and electro-mechanical features can now be integrated into chip-scale devices for use in biosensing and physiological measurements. Some of these devices have made enormous contributions in the study of complex biochemical processes occurring at the molecular and cellular levels while others overcame the challenges of replicating various functions of human organs as implant systems. This thesis presents test data and analysis of two such systems. First, an ISFET based pH sensor is characterized for its performance in a continuous pH monitoring application. Many of the basic properties of ISFETs including I-V characteristics, pH sensitivity and more importantly, its long term drift behavior have been investigated. A new theory based on frequent switching of electric field across the gate oxide to decrease the rate of current drift has been successfully implemented with the help of an automated data acquisition and switching system. The system was further tested for a range of duty cycles in order to accurately determine the minimum length of time required to fully reset the drift. Second, a microfluidic based vestibular implant system was tested for its underlying characteristics as a light sensor. A computer controlled tilt platform was then implemented to further test its sensitivity to inclinations and thus it‟s more important role as a tilt sensor. The sensor operates through means of optoelectronics and relies on the signals generated from photodiode arrays as a result of light being incident on them. ISFET results show a significant drop in the overall drift and good linear characteristics. The drift was seen to reset at less than an hour. The photodiodes show ideal I-V comparison between photoconductive and photovoltaic modes of operation with maximum responsivity at 400nm and a shunt resistance of 394 MΩ. Additionally, post-processing of the tilt sensor to incorporate the sensing fluids is outlined. Based on several test and fabrication results, a possible method of sealing the open cavity of the chip using a UV curable epoxy has been discussed.
ContributorsMamun, Samiha (Author) / Christen, Jennifer Blain (Thesis advisor) / Goryll, Michael (Committee member) / Yu, Hongyu (Committee member) / Arizona State University (Publisher)
Created2011
Description
During the last decades the development of the transistor and its continuous down-scaling allowed the appearance of cost effective wireless communication systems. New generation wideband wireless mobile systems demand high linearity, low power consumption and the low cost devices. Traditional RF systems are mainly analog-based circuitry. Contrary to digital circuits, the technology scaling results in reduction on the maximum voltage swing which makes RF design very challenging. Pushing the interface between the digital and analog boundary of the RF systems closer to the antenna becomes an attractive trend for modern RF devices. In order to take full advantages of the deep submicron CMOS technologies and digital signal processing (DSP), there is a strong trend towards the development of digital transmitter where the RF upconversion is part of the digital-to-analog conversion (DAC). This thesis presents a new digital intermediate frequency (IF) to RF transmitter for 2GHz wideband code division multiple access (W-CDMA). The proposed transmitter integrates a 3-level digital IF current-steering cell, an up-conversion mixer with a tuned load and an RF variable gain amplifier (RF VGA) with an embedded finite impulse response (FIR) reconstruction filter in the up-conversion path. A 4th-order 1.5-bit IF bandpass sigma delta modulator (BP SDM) is designed to support in-band SNR while the out-of-band quantization noise due to the noise shaping is suppressed by the embedded reconstruction filter to meet spectrum emission mask and ACPR requirements. The RF VGA provides 50dB power scaling in 10-dB steps with less than 1dB gain error. The design is fabricated in a 0.18um CMOS technology with a total core area of 0.8 x 1.6 mm2. The IC delivers 0dBm output power at 2GHz and it draws approximately 120mA from a 1.8V DC supply at the maximum output power. The measurement results proved that a digital-intensive digital IF to RF converter architecture can be successfully employed for WCDMA transmitter application.
ContributorsHan, Yongping (Author) / Kiaei, Sayfe (Thesis advisor) / Yu, Hongyu (Committee member) / Bakkaloglu, Bertan (Committee member) / Aberle, James T., 1961- (Committee member) / Barnaby, Hugh (Committee member) / Arizona State University (Publisher)
Created2012
Description
Advances in miniaturized sensors and wireless technologies have enabled mobile health systems for efficient healthcare. A mobile health system assists the physician to monitor the patient's progress remotely and provide quick feedbacks and suggestions in case of emergencies, which reduces the cost of healthcare without the expense of hospitalization. This work involves development of an innovative mobile health system with adaptive biofeedback mechanism and demonstrates the importance of biofeedback in accurate measurements of physiological parameters to facilitate the diagnosis in mobile health systems. Resting Metabolic Rate (RMR) assessment, a key aspect in the treatment of diet related health problems is considered as a model to demonstrate the importance of adaptive biofeedback in mobile health. A breathing biofeedback mechanism has been implemented with digital signal processing techniques for real-time visual and musical guidance to accurately measure the RMR. The effects of adaptive biofeedback with musical and visual guidance were assessed on 22 healthy subjects (12 men, 10 women). Eight RMR measurements were taken for each subject on different days under same conditions. It was observed the subjects unconsciously followed breathing biofeedback, yielding consistent and accurate measurements for the diagnosis. The coefficient of variation of the measured metabolic parameters decreased significantly (p < 0.05) for 20 subjects out of 22 subjects.
ContributorsKrishnan, Ranganath (Author) / Tao, Nongjian (Thesis advisor) / Forzani, Erica (Committee member) / Yu, Hongyu (Committee member) / Arizona State University (Publisher)
Created2012
Description
Energy harvesting from ambient is important to configuring Wireless Sensor Networks (WSN) for environmental data collecting. In this work, highly flexible thermoelectric generators (TEGs) have been studied and fabricated to supply power to the wireless sensor notes used for data collecting in hot spring environment. The fabricated flexible TEGs can be easily deployed on the uneven surface of heated rocks at the rim of hot springs. By employing the temperature gradient between the hot rock surface and the air, these TEGs can generate power to extend the battery lifetime of the sensor notes and therefore reduce multiple batteries changes where the environment is usually harsh in hot springs. Also, they show great promise for self-powered wireless sensor notes. Traditional thermoelectric material bismuth telluride (Bi2Te3) and advanced MEMS (Microelectromechanical systems) thin film techniques were used for the fabrication. Test results show that when a flexible TEG array with an area of 3.4cm2 was placed on the hot plate surface of 80°C in the air under room temperature, it had an open circuit voltage output of 17.6mV and a short circuit current output of 0.53mA. The generated power was approximately 7mW/m2.
On the other hand, high pressure, temperatures that can reach boiling, and the pH of different hot springs ranging from <2 to >9 make hot spring ecosystem a unique environment that is difficult to study. WSN allows many scientific studies in harsh environments that are not feasible with traditional instrumentation. However, wireless pH sensing for long time in situ data collection is still challenging for two reasons. First, the existing commercial-off-the-shelf pH meters are frequent calibration dependent; second, biofouling causes significant measurement error and drift. In this work, 2-dimentional graphene pH sensors were studied and calibration free graphene pH sensor prototypes were fabricated. Test result shows the resistance of the fabricated device changes linearly with the pH values (in the range of 3-11) in the surrounding liquid environment. Field tests show graphene layer greatly prevented the microbial fouling. Therefore, graphene pH sensors are promising candidates that can be effectively used for wireless pH sensing in exploration of hot spring ecosystems.
On the other hand, high pressure, temperatures that can reach boiling, and the pH of different hot springs ranging from <2 to >9 make hot spring ecosystem a unique environment that is difficult to study. WSN allows many scientific studies in harsh environments that are not feasible with traditional instrumentation. However, wireless pH sensing for long time in situ data collection is still challenging for two reasons. First, the existing commercial-off-the-shelf pH meters are frequent calibration dependent; second, biofouling causes significant measurement error and drift. In this work, 2-dimentional graphene pH sensors were studied and calibration free graphene pH sensor prototypes were fabricated. Test result shows the resistance of the fabricated device changes linearly with the pH values (in the range of 3-11) in the surrounding liquid environment. Field tests show graphene layer greatly prevented the microbial fouling. Therefore, graphene pH sensors are promising candidates that can be effectively used for wireless pH sensing in exploration of hot spring ecosystems.
ContributorsHan, Ruirui (Author) / Yu, Hongyu (Thesis advisor) / Jiang, Hanqing (Committee member) / Yu, Hongbin (Committee member) / Garnero, Edward (Committee member) / Li, Mingming (Committee member) / Arizona State University (Publisher)
Created2018
Description
The instrumentational measurement of seismic motion is important for a wide range of research fields and applications, such as seismology, geology, physics, civil engineering and harsh environment exploration. This report presents series approaches to develop Micro-Electro-Mechanical System (MEMS) enhanced inertial motion sensors including accelerometers, seismometers and inclinometers based on Molecular Electronic Transducers (MET) techniques.
Seismometers based on MET technology are attractive for planetary applications due to their high sensitivity, low noise floor, small size, absence of fragile mechanical moving parts and independence on the direction of sensitivity axis. By using MEMS techniques, a micro MET seismometer is developed with inter-electrode spacing close to 5 μm. The employment of MEMS improves the sensitivity of fabricated device to above 2500 V/(m/s2) under operating bias of 300 mV and input velocity of 8.4μm/s from 0.08Hz to 80Hz. The lowered hydrodynamic resistance by increasing the number of channels improves the self-noise to -135 dB equivalent to 18nG/√Hz (G=9.8m/s2) around 1.2 Hz.
Inspired by the advantages of combining MET and MEMS technologies on the development of seismometer, a feasibility study of development of a low frequency accelerometer utilizing MET technology with post-CMOS-compatible fabrication processes is performed. In the fabricated accelerometer, the complicated fabrication of mass-spring system in solid-state MEMS accelerometer is replaced with a much simpler post-CMOS-compatible process containing only deposition of a four-electrode MET structure on a planar substrate, and a liquid inertia mass of an electrolyte droplet. With a specific design of 3D printing based package and replace water based iodide solution by room temperature ionic liquid based electrolyte, the sensitivity relative to the ground motion can reach 103.69V/g, with the resolution of 5.25μG/√Hz at 1Hz.
By combining MET techniques and Zn-Cu electrochemical cell (Galvanic cell), this letter demonstrates a passive motion sensor powered by self-electrochemistry energy, named “Battery Accelerometer”. The experimental results indicated the peak sensitivity of battery accelerometer at its resonant frequency 18Hz is 10.4V/G with the resolution of 1.71μG without power consumption.
Seismometers based on MET technology are attractive for planetary applications due to their high sensitivity, low noise floor, small size, absence of fragile mechanical moving parts and independence on the direction of sensitivity axis. By using MEMS techniques, a micro MET seismometer is developed with inter-electrode spacing close to 5 μm. The employment of MEMS improves the sensitivity of fabricated device to above 2500 V/(m/s2) under operating bias of 300 mV and input velocity of 8.4μm/s from 0.08Hz to 80Hz. The lowered hydrodynamic resistance by increasing the number of channels improves the self-noise to -135 dB equivalent to 18nG/√Hz (G=9.8m/s2) around 1.2 Hz.
Inspired by the advantages of combining MET and MEMS technologies on the development of seismometer, a feasibility study of development of a low frequency accelerometer utilizing MET technology with post-CMOS-compatible fabrication processes is performed. In the fabricated accelerometer, the complicated fabrication of mass-spring system in solid-state MEMS accelerometer is replaced with a much simpler post-CMOS-compatible process containing only deposition of a four-electrode MET structure on a planar substrate, and a liquid inertia mass of an electrolyte droplet. With a specific design of 3D printing based package and replace water based iodide solution by room temperature ionic liquid based electrolyte, the sensitivity relative to the ground motion can reach 103.69V/g, with the resolution of 5.25μG/√Hz at 1Hz.
By combining MET techniques and Zn-Cu electrochemical cell (Galvanic cell), this letter demonstrates a passive motion sensor powered by self-electrochemistry energy, named “Battery Accelerometer”. The experimental results indicated the peak sensitivity of battery accelerometer at its resonant frequency 18Hz is 10.4V/G with the resolution of 1.71μG without power consumption.
ContributorsLiang, Mengbing (Author) / Yu, Hongyu (Thesis advisor) / Dai, Lenore (Committee member) / Kozicki, Michael (Committee member) / Jiang, Hanqing (Committee member) / Arizona State University (Publisher)
Created2016
Description
Ionic liquids (ILs), or low-temperature liquid salts, are a class of materials with unique and useful properties. Made up entirely of ions, ILs are remarkably tunable and diverse as cations and anions can be mixed and matched to yield desired properties. Because of this, IL/water systems range widely—from homogeneous mixtures to multiphasic systems featuring ionic liquid/liquid interfaces. Even more diversity is added when particles are introduced to these systems, as hard particles or soft-matter microgels interact with both ILs and water in complex ways. This work examines both miscible ionic liquid/water mixture and two-phase, immiscible ionic liquid/water systems. Extensive molecular dynamics (MD) simulations are utilized in conjunction with physical measurements to inform theoretical understanding of the nature of these systems, and this theoretical understanding is related to practical applications—in particular, the development of a low-temperature liquid electrolyte for use in molecular electronic transducer (MET) seismometers, and particle self-assembly and transport at ionic liquid/liquid interfaces such as those in Pickering emulsions.
The homogenous mixture of 1-butyl-3-methylimidazolium iodide and water is examined extensively through MD as well as physical characterization of properties. Molecular ordering within the liquid mixture is related to macroscopic properties. These mixtures are then used as the basis of an electrolyte with unusual characteristics, specifically a wide liquid temperature range with an extremely low lower bound combined with relatively low viscosity allowing excellent performance in the MET sensor. Electrolyte performance is further improved by the addition of fullerene nanoparticles, which dramatically increase device sensitivity. The reasons behind this effect are explored by testing the effect of graphene surface size and through MD simulations of fullerene and a silica nanoparticle (for contrast) in [BMIM][I]/water mixtures.
Immiscible ionic liquid/water systems are explored through MD studies of particles at IL/water interfaces. By increasing the concentration of hydrophobic nanoparticles at the IL/water interface, one study discovers the formation of a commingled IL/water/particle pseudo-phase, and relates this discovery to previously-observed unique behaviors of these interfaces, particularly spontaneous particle transport across the interface. The other study demonstrates that IL hydrophobicity can influence the deformation of thermo-responsive soft particles at the liquid/liquid interface.
The homogenous mixture of 1-butyl-3-methylimidazolium iodide and water is examined extensively through MD as well as physical characterization of properties. Molecular ordering within the liquid mixture is related to macroscopic properties. These mixtures are then used as the basis of an electrolyte with unusual characteristics, specifically a wide liquid temperature range with an extremely low lower bound combined with relatively low viscosity allowing excellent performance in the MET sensor. Electrolyte performance is further improved by the addition of fullerene nanoparticles, which dramatically increase device sensitivity. The reasons behind this effect are explored by testing the effect of graphene surface size and through MD simulations of fullerene and a silica nanoparticle (for contrast) in [BMIM][I]/water mixtures.
Immiscible ionic liquid/water systems are explored through MD studies of particles at IL/water interfaces. By increasing the concentration of hydrophobic nanoparticles at the IL/water interface, one study discovers the formation of a commingled IL/water/particle pseudo-phase, and relates this discovery to previously-observed unique behaviors of these interfaces, particularly spontaneous particle transport across the interface. The other study demonstrates that IL hydrophobicity can influence the deformation of thermo-responsive soft particles at the liquid/liquid interface.
ContributorsNickerson, Stella Day (Author) / Dai, Lenore L (Thesis advisor) / Yu, Hongyu (Committee member) / Lind, Mary Laura (Committee member) / Mu, Bin (Committee member) / Emady, Heather (Committee member) / Arizona State University (Publisher)
Created2016
Description
High Impedance Surfaces (HISs), which have been investigated extensively, have proven to be very efficient ground planes for low profile antenna applications due to their unique reflection phase characteristics. Another emerging research field among the microwave and antenna technologies is the design of flexible antennas and microwave circuits to be utilized in conformal applications. The combination of those two research topics gives birth to a third one, namely the design of Conformal or Flexible HISs (FHISs), which is the main subject of this dissertation. The problems associated with the FHISs are twofold: characterization and physical realization. The characterization involves the analysis of scattering properties of FHISs in the presence of plane wave and localized sources. For this purpose, an approximate analytical method is developed to characterize the reflection properties of a cylindrically curved FHIS. The effects of curvature on the reflection phase of the curved FHISs are examined. Furthermore, the effects of different types of currents, specifically the ones inherent to finite sized periodic structures, on the reflection phase characteristics are observed. After the reflection phase characterization of curved HISs, the performance of dipole antennas located in close proximity to a curved HIS are investigated, and the results are compared with the flat case. Different types of resonances that may occur for such a low-profile antenna application are discussed. The effects of curvature on the radiation performance of antennas are examined. Commercially available flexible materials are relatively thin which degrades the bandwidth of HISs. Another practical aspect, which is related to the substrate thickness, is the compactness of the surface. Because of the design limitations of conventional HISs, it is not possible to miniaturize the HIS and increase the bandwidth, simultaneously. To overcome this drawback, a novel HIS is proposed with a periodically perforated ground plane. Copper plated through holes are extremely vulnerable to bending and should be avoided at the bending parts of flexible circuits. Fortunately, if designed properly, the perforations on the ground plane may result in suppression of surface waves. Hence, metallic posts can be eliminated without hindering the surface wave suppression properties of HISs.
ContributorsDurgun, Ahmet Cemal (Author) / Balanis, Constantine A (Thesis advisor) / Aberle, James T (Committee member) / Yu, Hongyu (Committee member) / Bakkaloglu, Bertan (Committee member) / Arizona State University (Publisher)
Created2013
Description
Different environmental factors, such as ultraviolet radiation (UV), relative humidity (RH) and the presence of reducing gases (acetone and ethanol), play an important role in the daily life of human beings. UV is very important in a number of areas, such as astronomy, resin curing of polymeric materials, combustion engineering, water purification, flame detection and biological effects with more recent proposals like early missile plume detection, secure space-to-space communications and pollution monitoring. RH is a very common parameter in the environment. It is essential not only for human comfort, but also for a broad spectrum of industries and technologies. There is a substantial interest in the development of RH sensors for applications in monitoring moisture level at home, in clean rooms, cryogenic processes, medical and food science, and so on. The concentration of acetone and other ketone bodies in the exhaled air can serve as an express noninvasive diagnosis of ketosis. Meanwhile, driving under the influence of alcohol is a serious traffic violation and this kind of deviant behavior causes many accidents and deaths on the highway. Therefore, the detection of ethanol in breath is usually used as a quick and reliable screening method for the sobriety checkpoint. Traditionally, semiconductor metal oxide sensors are the major candidates employed in the sensing applications mentioned above. However, they suffer from the low sensitivity, poor selectivity and huge power consumption. In this dissertation, Zinc Oxide (ZnO) based Film Bulk Acoustic Resonator (FBAR) was developed to monitor UV, RH, acetone and ethanol in the environment. FBAR generally consists of a sputtered piezoelectric thin film (ZnO/AlN) sandwiched between two electrodes. It has been well developed both as filters and as high sensitivity mass sensors in recent years. FBAR offers high sensitivity and excellent selectivity for various environment monitoring applications. As the sensing signal is in the frequency domain, FABR has the potential to be incorporated in a wireless sensor network for remote sensing. This study extended our current knowledge of FBAR and pointed out feasible directions for future exploration.
ContributorsQiu, Xiaotun (Author) / Yu, Hongyu (Thesis advisor) / Christen, Jennifer Blain (Committee member) / Aberle, James T., 1961- (Committee member) / Jiang, Hanqing (Committee member) / Arizona State University (Publisher)
Created2011