Development of high-density photonic sensor chips

Robert MagnussonElectrical & Computer Engineering

University of Connecticut

and

Resonant Sensors Incorporated

NSF workshop on Biosensing and Bioactuation

27-28 November 2007

University of Maryland

Magnusson, Electrical&Computer Engr, University of Connecticut, and Resonant Sensors Inc. 2

Guided-mode resonance sensor Concept

Transmitted wave

Incident wave

Detected solution/gas nC

Waveguide- grating (nL, nH)

d

Reflected wave

Optical fiber, nF

Antigen Antibody Chemical link layer Grating surface

Deposited material nD

D

Selective sensing enabled with standard biochemical recognition reactions

-Antigen-antibody, enzyme-substrate, ligand-receptor, DNA

- No fluorescent/absorption tags required

Magnusson, Electrical&Computer Engr, University of Connecticut, and Resonant Sensors Inc. 3

Motivation for R&D: Important applications

• Pharmaceutical drug discovery – Increase the rate of identifying promising new drugs– Decrease the cost and time to market – Ability to screen arrays of analytes in high volume

• Homeland/environmental security– Accurate and low-cost detection of toxic materials (including

bacteria) in air and/or water environments

• Key requirements of these applications:• Low cost of equipment and operation• Minimize false readings, maximize detection sensitivity• Real time• Direct detection (tag-free sensing)• High throughput assays• Flexibility in system design and footprint

Magnusson, Electrical&Computer Engr, University of Connecticut, and Resonant Sensors Inc. 4

Fast - instant resultsOutstanding accuracy – cross

referenced dataHigh sensitivity – detection of small

molecules to large bacteria High resolution – sharp detection

peaks, high signal to noiseMass producible – high density

formats

Initial market applications in drug discovery and proteomics:

• Antigen-antibody assays, peptides and cell-based assays, DNA arrays Captured biomolecules

Change in reflected color of light

(1) Baseline

(2) After analyte

binds

Wavelength () R

efle

ctan

ce

Sensor element

Guided-mode resonance sensor technology Positive attributes

Magnusson, Electrical&Computer Engr, University of Connecticut, and Resonant Sensors Inc. 5

Chief GMR sensor features

Feature GMR sensor attribute

Polarization Arbitrary; pure TE or TM polarization state is often convenient.

Incidence angle Any, including zero.

Mode structureComplex; higher modes can provide new peaks for added sensitivity and accuracy.

Typical linewidth~1-10 nm, controlled by refractive index contrast of grating and fill factor.

SensitivityHigh; computed estimates ~10-6 refractive index and ~10-2 nm in thickness. Can be aided with polarization diversity and additional resonance peaks.

Accuracy High; narrow resonance peaks, cross-referenced in polarization.

Efficiency High; near 100% experimentally demonstrated.

Magnusson, Electrical&Computer Engr, University of Connecticut, and Resonant Sensors Inc. 6

Assay processing comparison

FeaturesCurrent label-based approaches

Guided-mode resonance sensor system

Time to measure biochemical reaction 4-24 hours (typical). <15-30 minutes (typical).

Chemical processing to detect biochemical reaction

2-3 incubation steps and 10-15 washing steps before readout.

Real-time, direct monitoring of biochemical reaction.

SensitivitypM range (commercial benchtop plate readers). pM to fM range

Binding kinetics not capable yes

Distinguish binding events from background refractive index/density changes not capable

yes; able to quantify background index and distinguish from binding event.

Magnusson, Electrical&Computer Engr, University of Connecticut, and Resonant Sensors Inc. 7

Polarization diversity in GMR biosensing

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20

Time (minutes)

Reso

nan

ce P

eak S

hif

t (n

m)

TE polz, 25% milk

TM polz, 25% milk

TE polz, 75% milk

TM polz, 75% milk

Sensor element

Streptavidin Biotin

Silane

GMR sensor element

AnalyteAntibody

Detector array(TE and TM polarizations)

Laser

Multiple resonance peaks allow the user to potentially distinguish background density changes from a targeted reaction

Magnusson, Electrical&Computer Engr, University of Connecticut, and Resonant Sensors Inc. 8

Resonant optical sensor technologySummary

• New enabling sensor technology– Performance leap wrt existing technology– Integratable, planar, thin, mass-producible; biochip format

possible– No labels needed– Strongest combination of performance/engineering issues in a

photonic sensor

• Applications– Drug discovery/development - HTS– Water/food/air monitoring– Sensing biomolecules and chemicals– Medical diagnosis/genomics– Homeland security– Environmental integrity assurance

Magnusson, Electrical&Computer Engr, University of Connecticut, and Resonant Sensors Inc. 9

Chief challengesGeneralizable to other sensor technologies

• Integrating the sensor chips with signal extraction- and data processing electronics consuming low power.• Incorporating exact electromagnetic inversion codes and wireless signal transmission capability into the electronics. • Deployment in sensor network architectures. • Developing economic fabrication technology for ~10,000 sensor pixels/cm2 (nanoimprint lithography).• Rapidly, accurately sensitizing high-density pixel arrays with proper antibodies, chemical links, etc. (nanorobotics).• Integrating arrays into microfluidic systems for sensor regeneration and redeployment under remote control or automatic response to environmental changes (smart sensor).• Designing highly sensitive elements for air and water operation, robust under a variety of environmental conditions. • Developing reliable, light-weight, compact, self-powered systems that are portable and patient/nurse/soldier etc. operable.