surface plasmon resonance - research - uwee€¦ · reduction in peripheral components without loss...

In commercial and research arenas, SPR is a popular transduction mechanismfor both benchtop and portable sensing systems that is both highly sensitive andreadily functionalized to sense a wide variety of chemical and biological agents.

Surface Plasmon Resonance Portable Biochemical Sensing Systems

National Science Foundation # ECS0300537

Biacore (the very big) To the very small?

A collaboration between Prof. Karl Booksh at Arizona State University andProf. Denise Wilson at the University of Washington seeks to develop anaccurate, but Very Small SPR-based sensing system.



Reduction in the “footprint” of anysingle component of the SPR system,in and of itself, compromisesperformance for portability.



Component Size

Light Source

Input Optics

Sensor

Output Optics

Photodetection

Signal Processing

LowFullPortable

ModeratePartialPortable

HighNoneTraditional

AccuracyLevel ofIntegration

Approach

Component Size

Light Source

Input Optics

Sensor

Output Optics

Photodetection

Signal Processing



HighFullPortable

HighPartialPortable

HighNoneTraditional

AccuracyLevel ofIntegration

Approach

Comparable performance can betargeted by considering the redesignof all components at once, as asystem whose quality exceeds thesum of performance of individualcomponents.

Reduction in peripheral components without loss of performance in SPR-basedsystems can be done by:



(c) Compressing thesignal processing toa single integratedcircuit (chip).

(a) Choosing a systemconfigurationamenable tominiaturization.

(b) Converting theoptical path fromdiscrete componentsto integrated fiberoptic components;

Surface Plasmon Resonance System Configuration: How it Works

When the wave vectorclosely matches that ofthe surface plasmon atthe metal-sampleinterface, reflected lightis significantlyattenuated

Optical Fiber w/ Cladding Gold Coating

Exposed Core

Metal

_inc

Sample

Substrate

EvanescentWave

Surface Plasma Wave

IncidentLight

ReflectedLight

ko = 2π/λ

Surface Plasmon Resonance System Configuration: Portable Probe Design

By placing a mirror at the end of theprobe, output light is reflected back inthe same direction as the input. Thus,the probe can be inserted into asensing overhead (no samplingrequired) rather than requiring thesensing solution to be “passed by” theSPR sensor (considerable samplingoverhead).

Surface Plasmon Resonance System Configuration: Portable Optics Path

The point at which SPRoccurs can be detected at a:

– Particular angle (constantwavelength interrogation)

– Particular wavelength (constantangle interrogation)

Constant Angle is chosen herebecause it enables aninexpensive light source(LED), easy and stable opticalalignment, and simpler, morecompact configuration.

Surface Plasmon Resonance Signal Processing:

(Cumbersome) Traditional Approach

High ResolutionPhotodetection

Communication/ADC Overhead

Measurement toReference Ratio

High ResolutionRegression

Software

Approach #1 (Traditional)MultivariateCalibration

In the traditional approach, many, many photodetector signals arescanned off of the sensing plane and then transferred to a PC forsignal processing


(Partial) Integrated Approach

MultivariateCalibration

Low ResolutionPhotodetection

Integration TimeProgramming

“Flatlining”Reference Ratio

Low ResolutionRegression

Software

Approach #2 (Voltage-Mode, Partially Integrated)

In the partially integrated approach, a much smaller number ofcustom photodetector signals are integrated in a “smart” way andthen transferred to a PC for signal processing


(Cumbersome) Traditional Approach

High ResolutionPhotodetection

Communication/ADC Overhead

Measurement toReference Ratio

High ResolutionRegression

Software

Approach #1 (Traditional)MultivariateCalibration

In the traditional approach, many, many photodetector signals arescanned off of the sensing plane and then transferred to a PC forsignal processing


(Fully) Integrated Approach

In the first fully integrated approach, all signals are processed on thesensing (photodetection) plane using both current-mode and pulse-mode arithmetic operations.



“Flatlining”Current Scaling

Conversion toPulse Mode


Software

Approach #3 (Pulse-Mode, Fully Integrated)


(Fully) Integrated Approach

In the second fully integrated approach, all signals are processed onthe sensing (photodetection) plane using current-mode arithmeticoperations which significantly reduces circuit size and complexity.



Dark CurrentCompensation

“Flatlining”Current Scaling


Software

Approach #4 (Current-Mode, Fully Integrated)

Surface Plasmon Resonance Portable Systems: Do they work?

Idark

...

...

Sp_0 Sp_1

6/6

6/6 6/9

6/9

4/44/44/4

6/6

6/6

6/12

6/12

Sp_7

Vdd

Mdark*Idark

VbiasVset

(a)

CholdVbuff

Vi

18/6

Vi’Vi”

Hold18/6

6/6 6/6

18/6

6/6

6/12

6/6

18/6

6/6

6/66/12

15/6 C

Precharge

18/6

6/6

18/6

6/6

Vcomp

18/6

6/6

6/6

18/6

6/6

Vi Vref

Approach #4

Approach #2

Approach #3

All (CMOS)Integrated approaches

are operational, asindividual circuits,

but how do theyperform in the

system?

Reduction in peripheral components without loss of performance in SPR-basedsystems can indeed be done by:

Surface Plasmon Resonance Creating System Portability:Can it be Done Effectively?

(c) Compressing thesignal processing toa single integratedcircuit (chip).

(a) Choosing a systemconfigurationamenable tominiaturization.

(b) Converting theoptical path fromdiscrete componentsto integrated fiberoptic components;

Surface Plasmon Resonance Output Generated by Portable Approach

Clearly Indicates point of Resonance

Air

Raw Data (background overwhelms resonance)Referenced Data (Resonance is evident)

Increasing RI

Surface Plasmon Resonance Comparable Performance is Achieved!

6.8 X 10-4

2.54%Current Mode

6.9 X 10-42 X 10-45 X 10-4RI Resolution2.72%3.53%6.07%Prediction Error

Pulse ModeVoltage ModeTraditionalApproach

200 X 1000FullCurrent Mode

200 X 1200FullPulse Mode

200 X 1800PartialVoltage Mode

BigNoneTraditional

Size(λ X λ )

Level ofIntegration

Approach

Surface Plasmon Resonance The Story of Portable Systems


Pixel

AnalogSampling

DigitalControl

Phototransistor

The End

2mm

surface plasmon resonance - research - uwee€¦ · reduction in peripheral components without loss...

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