Surface Plasmon Resonance
Portable Biochemical Sensing Systems
Karl Booksh
School of Biochemistry
Arizona State University (Tempe)
Denise Wilson
Department of Electrical Engineering
University of Washington (Seattle)
National Science Foundation, Grant #ECS0300537
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
ECS0300537
• The Big Picture
– Why SPR?
•
•
•
•
•
Highly sensitive (10-4 to 10-6 RI units)
Very local (10-100nm from sensing surface)
Directly indicative (of interactions between sensor and environment)
Relatively unencumbered by sampling overhead (e.g. tagging, mixing, etc)
Readily referenced to compensate for background fluctuations (e.g. drift)
– How is it used (SPR = transduction mechanism)?
• Non-functionalized = bulk refractive index
• Functionalized = specific analytes
– The Full Spectrum of SPR-based instruments
• User-Intensive, Single Measurements: Biacore
• User-Intensive, Single Field Measurements: TI Spreeta (Chinowsky/Yee)
• Distributed and Autonomous, Multiple Measurements:
– Insertion-based probes
– Compact signal processing
– Streamlined, robust optical path
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
• Who are we?
– Karl Booksh, Biochemistry, Arizona State University (Probes and Functionalization)
– Denise Wilson, Electrical Engineering, University of Washington (Signal Processing and
Systems Integration)
– Are we interdisciplinary? Tight integration of biochemistry and electrical engineering
• Goal of this Research
– Surface Plasmon Resonance
• Field monitoring at numerous locations
• What defines the problem?
– Ability to sense specific analytes at high sensitivity/low detection limit
– With high resilience to ambient fluctuations
• light, temperature,
• other factors that influence bulk refractive index
– In a manner that allows continuous sampling with little overhead
– In a footprint that is non-intrusive or easily carried (handheld)
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
Basic Operation
Sample
Metal
Surface Plasma Wave
Evanescent
Wave
θinc
Substrate
Incident
Light
Optical Fiber w/ Cladding
When the wave vector
closely matches that of
the surface plasmon at
the metal-sample
interface, reflected light
is significantly attenuated
Reflected
Light
Gold Coating
Exposed Core
ko = 2p/l
Surface Plasmon Resonance
Portable Biochemical Sensing
Systems Configurations
• Point of resonance can be
detected at a
– Particular angle (constant
wavelengh interrogation)
– Particular wavelength (constant
angle interrogation)
• Constant Angle
– Polychromatic light source at
constant angle of incidence
• Constant Wavelength
– Monochromatic light source at
different angles of incidence
Constant Angle is chosen here for: inexpensive light source, easy
alignment, and simpler, more compact configuration (= less overhead)
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
Sensor Design
Sampling Options:
• In-line
• “Dip” insertionbased probe
The probe configuration is :
• easily replaced, easy to use
• Less prone to sensor layer blocking,
but can be
• more sensitive to ambient fluctuations
• more susceptible to fouling
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
Typical Output
Air
Increasing RI
Raw Data (background overwhelms resonance)
Referenced Data (Resonance is evident)
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
Summary of Effort
Multivariate
Calibration
Approach #1 (Traditional)
Software
High Resolution
Photodetection
Communication/
ADC Overhead
Measurement to
Reference Ratio
Approach #2 (Voltage-Mode, Partially Integrated)
Low Resolution
Photodetection
Integration Time
Programming
“Flatlining”
Reference Ratio
High Resolution
Regression
Multivariate
Calibration
Software
Low Resolution
Regression
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
Summary of Effort
Approach #3 (Pulse-Mode, Fully Integrated)
Multivariate
Calibration
Software
Low Resolution
Photodetection
“Flatlining”
Current Scaling
Conversion to
Pulse Mode
Approach #4 (Current-Mode, Fully Integrated)
Low Resolution
Regression
Multivariate
Calibration
Software
Low Resolution
Photodetection
Dark Current
Compensation
“Flatlining”
Current Scaling
Low Resolution
Regression
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
System-on-Chip Implementations
Approach #2
All Designs are
mixed signal,
fabricated in
standard CMOS
Approach #4
6 /12...
6 /6
6 /6
6 /12...
6 /6
6 /6
4 /4
Sp_0
Sp_1
4 /4
Sp_7
Vdd
6 /9
18/6
18/6
18/6
18/6
6/6
6 /9
Vbuff
4 /4
6/6
6/12
Chold
Vi Σ
Precharg e
ViΥ
6/12
18/6
18/6
18/6
6/6
6/6
18/6
Vi
Vi
Vref
6/6
Vcomp
6/6
Vbias
6/6
Approach #3
Vset
Idark
Mdark*Idark
(a)
C
15/6
Hold
6/6
6/6
6/6
6/6
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
System-on-Chip Implementations
Pixel
Analog
Sampling
Digital
Control
2mm
Phototransistor
15 pixel array
fabricated on a
1cm2 die in the
1.5 micron AMI
process through
MOSIS
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
System-on-Chip Implementations
Approach
SOC
Integration
Size
(l X l )
Traditional
None
Big
Voltage Mode
Partial
200 X 1800
Pulse Mode
Full
200 X 1200
Current Mode
Full
200 X 1000
Current Mode
Approach
Traditional
Voltage Mode
Pulse Mode
Prediction Error
6.07%
6.05%
7.8%
RI Resolution
5 X 10-4
2 X 10-4
6 X 10-4
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
• What’s the bottom line?
– Benchmarking has shown system-on-chip to be competitive with software solutions
– Compact, low user-overhead, low-power SPR nodes have been enabled:
• Environmental Monitoring (e.g. coastal/ocean/freshwater)
• Denise sensor networks for maintaining public safety (e.g. water supply)
• Biomedical applications (e.g. point of care, preventative heart attack
monitoring)
– Students (3 MS, 2 undergraduate, 2 of which are women)
– Outreach/Broader Impact
• SPR modeling and simulation integrated into electronic nose toolbox
• www.ee.washington.edu/research/enose
– Technology Transfer
• Probe design is patented and licensed to two companies in Phoenix
• SOC designs are fabricated in standard CMOS
• Optical components are modular and readily available
Surface Plasmon Resonance
Portable Biochemical Sensing Systems
• Publications
– Denise M. Wilson and Lisa E. Hansen, “Current-mode System-on-Chip for SPR Sensing
Systems,” IEEE Sensors Journal, submitted for publication, June 2006.
– Lisa E. Hansen and Denise M. Wilson, “System-on-chip Surface Plasmon Resonance Sensors
Using Pulse-based Interface Circuits,” IEEE Sensors Journal, submitted for publication,
March 2006.
– M.W. Johnston, Lisa E. Hansen, and Denise M. Wilson, “System-on-Chip Circuit Architecture
for Eliminating Interferents in Surface Plasmon Resonance Sensing Systems,” IEEE Sensors
Journal, submitted for publication, January 2006.
– Lisa E. Hansen, Matthew Johnston, and Denise M. Wilson, “System-on-chip Surface Plasmon
Resonance Sensors Using Pulse-based Interface Circuits,” IEEE Sensors: Irvine, California,
October 2005.
– Matthew Johnston, Denise Wilson, Karl Booksh, and Jeffrey Cramer, “Integrated Optical
Computing: System on Chip for Surface Plasmon Resonance Imaging,” Intl. Symp. Circuits
and Systems, ISCAS: Kobe, Japan, May 2005.
– Lisa Hansen, Matthew Johnston, and Denise Wilson, “Pulse-based Interface Circuits for SPR
Sensing Systems,” Intl. Symp. Circuits and Systems, ISCAS: Kobe, Japan, May 2005.
– Denise M. Wilson, Mike Warren, Karl Booksh, and Louis Obando, “Integrated Optical
Computing for Portable, Real-time SPR Analysis of Environmental Pollutants,” Eurosensors
2002: Prague, Czech Republic, September 2002.