Surface Plasmon Resonance Portable Biochemical Sensing Systems

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1 Karl Booksh School of Biochemistry Arizona State University (Tempe) Denise Wilson Department of Electrical Engineering University of Washington (Seattle) National Science Foundation, Grant #ECS ECS 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 1

2 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 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) Basic Operation Sample Metal Substrate Evanescent Wave Incident Light θ inc Surface Plasma Wave Reflected Light When the wave vector closely matches that of the surface plasmon at the metal-sample interface, reflected light is significantly attenuated Optical Fiber w/ Cladding Gold Coating Exposed Core k o = 2π/λ 2

3 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) 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 3

4 Typical Output Air Increasing RI Raw Data (background overwhelms resonance) Referenced Data (Resonance is evident) Summary of Effort Approach #1 (Traditional) High Resolution Communication/ ADC Overhead Measurement to Reference Ratio High Resolution Approach #2 (Voltage-Mode, Partially Integrated) Integration Time Programming Flatlining Reference Ratio 4

5 Summary of Effort Approach #3 (Pulse-Mode, Fully Integrated) Flatlining Current Scaling Conversion to Pulse Mode Approach #4 (Current-Mode, Fully Integrated) Dark Current Compensation Flatlining Current Scaling System-on-Chip Implementations Approach #2 All Designs are mixed signal, fabricated in standard CMOS Approach #4 V dd 6/ /9 6/ /9 S p_0 4/4 4/4 4/4 S p_1 S p_7 18/6 18/6 18/6 V buff 18/6 15/6 C Hold V i 6/12 Precharge V i Ó V i Õ 6/12 C hold 18/6 18/6 V i V comp 18/6 V ref 18/6 V bias I dark V set M dark* I dark Approach #3 (a) 5

6 System-on-Chip Implementations Pixel Analog Sampling Phototransistor Digital Control 2mm 15 pixel array fabricated on a 1cm 2 die in the 1.5 micron AMI process through MOSIS System-on-Chip Implementations Approach Traditional Voltage Mode Pulse Mode Current Mode SOC Integration None Partial Full Full Size (λ X λ ) Big 200 X X X 1000 Approach Traditional Voltage Mode Pulse Mode Current Mode Prediction Error 6.07% 6.05% 7.8% RI Resolution 5 X X X

7 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 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 Publications Denise M. Wilson and Lisa E. Hansen, Current-mode System-on-Chip for SPR Sensing Systems, IEEE Sensors Journal, submitted for publication, June Lisa E. Hansen and Denise M. Wilson, System-on-chip Sensors Using Pulse-based Interface Circuits, IEEE Sensors Journal, submitted for publication, March M.W. Johnston, Lisa E. Hansen, and Denise M. Wilson, System-on-Chip Circuit Architecture for Eliminating Interferents in Sensing Systems, IEEE Sensors Journal, submitted for publication, January 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 Matthew Johnston, Denise Wilson, Karl Booksh, and Jeffrey Cramer, Integrated Optical Computing: System on Chip for Imaging, Intl. Symp. Circuits and Systems, ISCAS: Kobe, Japan, May Lisa Hansen, Matthew Johnston, and Denise Wilson, Pulse-based Interface Circuits for SPR Sensing Systems, Intl. Symp. Circuits and Systems, ISCAS: Kobe, Japan, May 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