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Current
Research
Multi-function
Microsystem for Electrochemical Biosensor Array
Monolithic gas sensor
array for health and safety monitoring
Post CMOS fabrication
for the integration of CMOS and electrochemical biosensors
Wearable
Autonomous Microsystem with Electrochemical Gas Sensor Array for Real-Time
Health and Safety Monitoring
Gas sensor array signal processing
Previous Research
A Neural Signal Processor for Wireless
Implants
Low power, low noise, multi-channel
implanted neural interface circuit
Post CMOS fabrication for
electrochemical measurement of biointerface
Electrochemical
Microsystem Array for Functional Proteomics
Chemiresistor
Instrumentation
On-Chip Amperometric Readout of Electrochemical Sensors
AMSaC Mixed Signal Generic Test Board
Highly Adaptive Multi-Sensor
Readout and Communication Interface Circuits
Process-Scalable
Optimization of Wide-Issue Superscalar Microprocessors
On-Chip Readout of Electrochemical
Sensors: CMOS Potentiostats and Impedance Spectroscopy
Multi-function
Microsystem for Electrochemical Biosensor Array
 Description: An on-chip biosensor array CMOS
microsystem provides a low-cost, high accuracy, and parallel measurement
solution for biosensor detection and quantification. The goal of this project
is to develop an integrated microsystem platform that incorporates a
bio-interface array into a continuous-use, cost-effective, electrochemical
characterization system suitable for DNA, protein, and enzyme detection and
quantification. To achieve the benefits of this miniaturized microsystem,
compact, ultra-low power and high sensitivity CMOS biosensor CMOS
instrument circuits are extremely necessary. A multi-function readout
circuit, stimulus signal generator and potentiostat blocks are integrated into
one single chip.
Investigators: Xiaowen Liu
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Monolithic gas sensor array for health and safety monitoring
Description: The growing potential impact of airborne
pollutants on personal health and safety has propelled the demand for
hand-held sensor device to monitor hazardous gases. Miniaturization of a
sensor system would gain benefits of low cost, low power, small size for such
hand-held sensor device. This project aims to develop a new type of
miniaturized gas sensor system that utilizes room temperature ionic liquid
sensor and electrochemical instrumentation. A new sensor structure with
electrodes on a permeable membrane has been developed to achieve rapid gas
sensing response. A monolithic sensor-on-chip solution is now being explored
to integrate both sensor arrays and instrumentation on a single chip and
permits rapid sensing of hazardous gases.
Investigators: Xiaoyi Mu
Post CMOS fabrication for
the integration of CMOS and electrochemical biosensors
Description: The goal of this multidisciplinary
project is to develop an integrated microsystem platform that incorporates a
bio-interface array onto a CMOS of electrochemical circuitry that can perform
the sensing and measurement in real time. Electrochemical techniques such as
cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) are often
employed to characterize biosensor interface properties. Such techniques can
readily be implemented within CMOS instrumentation circuits. As part of
electrochemical microsystem project, this project mainly focuses on the
realization of on-chip electrochemical measurement. To achieve this goal,
post-CMOS fabrication needs to be developed including 1) on-chip gold
microelectrode array, 2) reliable test packaging scheme for experiments in
liquid environment which requires electrical insulation, 3) novel packaging
approach that can enable integration of microfluidic system. The challenge is
to apply conventional MEMS fabrication techniques to the specific CMOS chip
to meet all the requirements set by the biosensing application.
Investigators: Lin Li
Wearable
Autonomous Microsystem with Electrochemical Gas Sensor Array for Real-Time
Health and Safety Monitoring
Description: Exposure to air pollution
consistently ranks among the leading global causes of illness and
mortality, and explosive gases are an increasing threat to occupational
safety as energy demands rise. Although there have been many important
advances in gas sensor technologies, development of a wearable, autonomous
multi-analyte gas sensor system remains an open challenge. We are designing
a new system to meet the goals for environmental monitoring by integrating
sensor arrays, electronics, and data analysis algorithms into a thumb-drive
sized microsystem, called the intelligent electrochemical gas analysis
system, or iEGAS. A novel electrochemical (EC) sensor array was under
studied to improve selectivity and sensitivity. A novel multi-mode EC
instrumentation chip (MEIC) provides stimulus signals for the EC sensor
array and measures sensor response. A microcontroller (MCU) controls the
system, analyzes data and generates alert signals to warn users of adverse
conditions. A prototype iEGAS has been constructed which is able to read
sensor data and upload it in real time to a PC for display and storage. For
the next generation iEGAS, MEIC is under developement, and communications
between MEIC, MCU and PC are setting up.
Investigators: Haitao Li
Gas sensor array signal
processing
Description: An intelligent electrochemical
gas analysis system is an instrument that is used to measure target gases
in the air based on a gas sensor array. This project aims to develop a
hardware efficient algorithm to estimate concentrations of individual gases
within a real world mixture of gases. This project seeks to model the
sensor array as a system of nonlinear equations and simultaneously identify
and estimate concentration of target gases. A VLSI architecture is being
designed to implement the algorithm for low power and potable application.
Investigators: Yuning Yang
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A Neural Signal Processor for
Wireless Implants
 Description: This project aims to develop an
implantable system-on-chip for compressing real-time neural data recorded from
microelectrode arrays, permitting data from a large number of channels to
be wirelessly transmitted to external processing units. The on-chip
front-end signal processing and resulting compression must maintain the
distinctive features in the shape of neural spikes to enable high-quality
spike sorting at the receiver. The compression and transmission hardware
must be power efficient to avoid heating tissue, and area efficient to
facilitate surgical procedures. The proposed system contains analog, digital,
and RF circuits. Neural signals are amplified and digitized before being
transformed into time-frequency domain at the discrete wavelet transform
(DWT) block. Lossy compression at the threshold block is followed by
lossless compression in the run length encoder block. The compressed data
and configuration commands are communicated over a bi-directional
half-duplex wireless link to external processing units. The first iteration
of the DWT block was fabricated in a 0.5μm CMOS process. The circuit
supports 4 levels of wavelet decomposition and processes 32 neural data
channels pseudo-simultaneously. A second generation that permits the number
of channels recorded to be user determined has been designed in 0.13μm
CMOS and optimized for low power operation. This project is supported by
the National Institute of Health under award number 1R01NS062031.
Investigators: Awais M. Kamboh, Yuning Yang
Low power, low noise,
multi-channel implanted neural interface circuit
 Description: This project aims to build an interface circuit to detect the weak
neural signal from human brain. The
challenge is to achieve low power, low noise goal while consuming little
chip area. The preamplifier performance is the most critical part of the
system since it interfaces directly to µV level neural signal from the
electrodes. We have developed a preamplifier with transistors operating in
sub-threshold region in 0.5µm CMOS process. One SAR ADC is placed after 32
channels to convert the amplified, filtered analog signal into digital
signal for further digitized processing. All the modules are built on a
single chip.
Investigators: Haitao Li
Post CMOS fabrication
for electrochemical measurement of biointerface
 Description: With the completion of the Human Genome Project and the sequencing
of several other scientifically important genomes, emphasis has shifted to
determining the structure and function of the gene products, i.e., the
proteins. The goal of this multidisciplinary project is to develop an
integrated microsystem platform that incorporates a protein-based
bio-interface array into a continuous-use, cost-effective, electrochemical
characterization system suitable for functional proteomics research. As part
of electrochemical microsystem array project this project focuses mainly on
the the realization of on chip electrochemical measurement.To achieve this
goal, post-CMOS fabrication needs to be developed including 1) on-chip gold
microelectrode array, 2) reliable test packaging scheme for biotesting in
liquid environment which requires electrical insulation and microfluidic
system. The challenge is to apply conventional MEMS fabrication techniques
to the specific CMOS chip for liquid environment measurement.
Investigators: Lin Li
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Electrochemical
Microsystem Array for Functional Proteomics
 Description: With the completion of the Human Genome Project and the sequencing
of several other scientifically important genomes, emphasis has shifted to determining
the structure and function of the gene products, i.e., the proteins. The
goal of this multidisciplinary project is to develop an integrated
microsystem platform that incorporates a protein-based bio-interface array
into a continuous-use, cost-effective, electrochemical characterization
system suitable for functional proteomics research. To achieve this goal,
we have synergistically explored several technical challenges including: 1)
the development of novel nanostructured bio-interfaces appropriate for
integration on the surface of a microelectronics chip, 2) the design of
high performance integrated circuits for multiple electrochemical assays,
3) the design of circuits, structures, and packaging for on-chip thermal
control of individual bio-interface sites, and 4) the development of
microfabrication techniques enabling a miniaturized, multi-protein,
array-on-chip platform that incorporates fluid handling. Electrode arrays
on silicon have been fabricated and functionalized with nanostructured enzyme
and membrane protein interfaces. A new multi-channel electrochemical
impedance spectroscopy circuit, with on-chip AC stimulus generator, has
been implemented and provides a resolution of ~100fA and current range up
to 100nA Microhotplate arrays with thermal control circuitry has been
realized in standard CMOS and verified to control the temperature of
individual on-chip electrodes within the biological testing range. Several
packaging options are now being explored to integrate all the elements of
this microsystem platform and permit rapid functional characterization of a
wide range of proteins.
Investigators: Xiaowen Liu, Lin Li
Chemiresistor
Instrumentation
 Description: Chemiresistors (CR)
utilizing thiolate-monolayer-protected gold nanoparticles (MPN) as
interfacial layers form highly sensitive vapor sensors useful for air
quality monitoring, explosives detection, and breath analysis for health
screening. All of these applications require compact and inexpensive
instrumentation to realize their full potential. However, most CRs are
currently being interrogated with large and expensive bench top
instrumentation. Some chip-level solutions have been proposed for similar
resistance based gas sensors, but those solutions do not posses the
resolution required to make full use of the MPN CRs sensitivity. In
addition, the CR posses a capacitive response which has not been fully
explored, but may present additional information about the vapors being
detected. This project aims to develop a system integrating the CR sensor
itself and high resolution instrumentation on a single chip.
Investigators: Xiaoyi Mu and Daniel Rairigh
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On-Chip Amperometric
Readout of Electrochemical Sensors
Description: In order to realize chip-scale
bioelectrochemical systems, this project seeks to develop integrated
circuits that permit on-chip measurements using both electrochemical
impedance spectroscopy (EIS) and cyclic voltammetry techniques. Our
amperometric measurement approach utilizes a multi-function signal
generator for voltage stimulus and a current readout circuit with sub-pA
resolution. All circuits are implemented on a single chip, vastly reducing
the system size for electrochemical analysis and enabling for multi-channel
readout of electrochemical sensor arrays for a wide range of biological and
chemical detection applications. A key feature of this effort is the
development of a highly programmable signal generator that produces both AC
excitations with a wide frequency range as well as constant and cyclic DC
excitations, enhancing the capability and flexibility of the system.
Investigators: Waqar A. Qureshi, Liya Meng
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AMSaC Mixed Signal Generic
Test Board
 Description: We have
begun to develop a generic test board to verify the functions and to
evaluate the performance of our chips. The goal of this project is to provide
a platform for a broad variety of digital, analog and mixed signal chips.
This board acts not only as an electrical interface between the device
under test and the PC, but it also offers specific functionalities using
different types of onboard ASICs. To achieve as much flexibility as
possible, control signals and test stimuli are provided by a reprogrammable
FPGA. In order to reduce the time and effort to access and process the
data, a data acquisition card is used.
Investigators: Stefan Schorr
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Highly Adaptive
Multi-Sensor Readout and Communication Interface Circuits
Description: As a legacy of prior
work integrating multi-parameter microsystems, several generations of
sensor interface circuits have been developed. Early versions demonstrated
adaptability to different capacitive transducers. We then introduced a new
sensor bus structure uniquely tailored to integrated microsystems with
multiple intra-module sensor nodes. Utilizing this sensor bus, subsequently
developed interface circuits provided a very high level of readout
configurability and system flexibility. Our universal microsensor interface
(UMSI) chip achieved unprecedented adaptability to many different sensor
types and implemented numerous performance enhancing features, such as
online recalibration and mixed-signal actuator control, not available in
any other miniature, low-power, sensor interface circuit. We have also
recently incorporated these ideas into a new system-on-chip (SoC)
implementation with an embedded controller and a highly hardware-efficient
sensor readout block. This chip has won two prizes in an SoC design contest
sponsored by the Semiconductor Research Corporation, and is a finalist for
Best Student Paper in the upcoming IEEE Sensors Conference.
Investigators: Chao Yang, Jichun Zhang, Junwei Zhou
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 Process-Scalable Optimization
of Wide-Issue Superscalar Microprocessors
Description:
Combining
an understanding of circuit-level performance constraints with
architectural-level high throughput structures, we have analyzed the design
tradeoffs for wide-issue superscalar microprocessors as CMOS feature size
shrinks in the submicron regime. We have identified several effective
methods for decreasing delays in the processor instruction queue and
designed circuits to significantly reduce processor delays with negligible
performance loss. We have shown that our hardware banking/segmenting
approach can be adapted to match performance characteristics of different
wide-issue processors, enabling significant performance improvement for
both single program and multi-program workloads.
Investigators: Chao Yang, Jichun
Zhang, Junwei Zhou
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On-Chip Readout of Electrochemical
Sensors: CMOS Potentiostats and  Impedance Spectroscopy
Description: In unison with the topic above,
we have been developing the backbone circuitry necessary to realize
miniature bioelectrochemical systems with on-chip measurement electronics.
Utilizing state-of-the art mixed-signal integrated circuit techniques, we
developed a high performance potentiostat that can resolve sub-picoampere
currents, operate over six orders of magnitude in base current, and perform
on-chip cyclic voltammetry on a sensor array. This circuit is currently
being tested with electrochemical sensors for a journal paper to be
submitted by Dec. 2006. Electrochemical impedance spectroscopy (EIS) is
another important measurement technique for bio/chem-interfaces, but there
are no existing chip-scale EIS solutions.
We have analyzed several EIS techniques and evaluated their
feasibility for on-chip implementation with biological and chemical
sensors. We have created a new
methodology and circuit to rapidly perform EIS in the low frequency range
(invention disclosure filed), as necessary for many biosensors. With the
proliferation of nano-technology sensors in recent years, we anticipate
these chip-scale readout circuits, particularly EIS, to be critical for
next generation sensory systems.
Investigators: Chao Yang.
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