Biometric Sensing: Plasmonic Theory and Label-free Applications

University of Minnesota-DuluthEE4611: Semiconductor Physics and Devices

Joshua MacVeyDr. S. Burns

Outline• Biosensors: Introduction & Plasmonic Motivation

• Some Needed Background: What is a plasmon?

• Optical Biosensors

• Label-Free Biosensor: Surface Plasmon Biosensors• – Surface plasmon resonance biosensors: Qualitative• – Surface plasmon resonance biosensors: Quantitative

Outline• Biosensors: Introduction & Plasmonic Motivation• Some Needed Background: What is a plasmon?• Optical Biosensors• Label-Free Biosensor: Surface Plasmon Biosensors

• – Surface plasmon resonance biosensors: Qualitative• – Surface plasmon resonance biosensors: Quantitative

The Why & What of biosensors

• measure biomolecules:– Proteins– DNA – Etc.

• applications in:– Diagnostics– Drug researchAnd, of course… $$

Strong Growth Predicted for Biosensors Market

Extreme Generality

Broad Categories: Labeled vs label-free

What is labeling?• Attachment of a fluorescent marker to

biomolecule

• measure signal under laser excitation

+ =

lasersignal

CAN WE THINK OF ANY PROS AND CONS TO LABELING?

Label-free sensing

P

ΔP

Δλ

1.55 μm

Example: Ring-resonator

Sun, et. al (2010)

Plasmonic Nanophotonics: a logical next step?

Why plasmonics?

Outline• Biosensors: Introduction & Plasmonic Motivation• Some Needed Background: What is a plasmon?• Optical Biosensors• Label-Free Biosensor: Surface Plasmon Biosensors

• – Surface plasmon resonance biosensors: Qualitative & Theoretical

• – Surface plasmon resonance biosensors: Quantitative

What is a plasmon?A plasmon is a density wave in an electron gas - a collective oscillations of the free electron gas density. It is analogous to a sound wave, which is a density wave in a real gas of molecules.

Prof. Polman’s nanophotonic course@Amolf

What is a plasmon?Plasmons in the bulk oscillate at

determined by the free electron density and effective mass

Plasmons confined to surfaces that can interact with light to form propagating “surface plasmon polaritons (SPP)”

Confinement effects result in resonant SPP modes in nanoparticles

+ + +

- --

+ - +

k

m0

Prof. Polman’s nanophotonic course@Amolf

Ne2drude p Bulk plasmon

Surface plasmon

Localized Surface plasmon

Metal

Surface plasmon(or surface plasmon-polariton )

+ - +

kdielectric

Note: this is a TM wave

E

H

Localized Surface plasmon

Wavelength dependent local fieldintensity

Plasmon propagation in micro-/nano-wires

R. M. Dickson et al. J. Phys. Chem. B 104, 6095 (2000)B. Wild et al. ACS Nano 6, 472 (2011)

1µm

Applications of surface plasmons: An example device

Surface plasmon resonance biosensors

But before we get to this…

Outline• Biosensors: Introduction & Plasmonic Motivation• Some Needed Background: What is a plasmon?• Optical Biosensors• Label-Free Biosensor: Surface Plasmon Biosensors

• – Surface plasmon resonance biosensors: Qualitative• – Surface plasmon resonance biosensors: Quantitative

Approaches to enhance biosensingperformance

1. Enhancing sensitivityΔλ

Inte

nsity

Wavelength

low sensitivity

Δλ

Inte

nsity

Wavelength

high sensitivity

Approaches to enhance biosensingperformance

Inte

nsi

ty

Wavelength

FWHM

low Q-factor (low selectivity)

Δλ

Δλ

2. Enhancing selectivityhigh Q-factor (high selectivity)

P

λ

λSensitivity

Increases with increasing Q factor of the ring

Q resonance/

P

3dB

Outline• Biosensors: Introduction & Plasmonic Motivation• Some Needed Background: What is a plasmon?• Optical Biosensors• Label-Free Biosensor: Surface Plasmon Biosensors

• – Surface plasmon resonance biosensors: Qualitative• – Surface plasmon resonance biosensors: Quantitative

Theory: Surface Plasmons• Evanescent TM polarized electromagnetic waves bound to the surface

of a metal• Benefits for Biosensing

– High fields near the interface are very sensitive to refractive index changes

– Gold is very suitable for biochemistryFrom source

To detector

Prism

Gold

R

Dr. Peter Debackere’s Internal tutorial

Configurations: How can we excite SPP Modes?

Otto Configuration KretschmanConfiguration

Resonant MirrorConfiguration

Fiber optics Sensors WaveguideIntegrated SPR

LSPR nanosensor

Outline• Biosensors: Introduction & Plasmonic Motivation• Some Needed Background: What is a plasmon?• Optical Biosensors• Label-Free Biosensor: Surface Plasmon Biosensors

• – Surface plasmon resonance biosensors: Qualitative• – Surface plasmon resonance biosensors: Quantitative

Applications of surface plasmons: An example device

Surface plasmon resonance biosensors

And we’re back.

• Which metal ?Kretschmann : Design

Thickness of the Metal ?

Response Curves• Angular Response Spectral Response

Au thickness 44 nm, resonance angle 65.58 degrees, resonant wavelength 650 nm

Response Curves• Angular Response Spectral Response

Au thickness 44 nm, resonance angle 65.58 degrees, resonant wavelength 650 nm

65.61˚

65.71˚

657 nm

677 nm

Response Curves• Angular Response Spectral Response

22.73˚

22.75˚

1610 nm

1683 nm

Au-layer thickness 38 nm resonance angle 22.71 degrees resonance wavelength 1600

Sensitivity

15000

20000

25000

30000

35000

40000

Sensitivity [nm/RIU]

60000

65000

70000

75000

80000

85000

90000

1.5 1.651.55 1.6

Wavelength [um]

Sensitivity total contribution

spectral half width

440

420

400

380

360

340

1.53 1.58 1.63 1.68

BK 7 Glass Prism Silicon PrismSensitivity [nm/RIU] Wavelength shift [nm/RIU]

[nm/RIU] spectral half width

300250200150100500

0.6

0.8

1

Wavelength shift

Sensitivity total contribution

FRESN

10000

0.6 0.65 0.7 0.75 0.8 0.85 0.90.95

Wavelength [um]

Localized surface plasmon resonance (LSPR) biosensor

LSPR sensing streptavidin binding to biotin

LSPR biosensor consists of 3 major components

Plasmonic surface:signal transduction

Passivating layer: reduces nonspecific binding

Probe layer: recognize specific targets

Surface plasmon resonance (SPR) biosensor

Δλ=12.7nm

SPR sensing streptavidin binding to biotin

Ag

Single nanoparticle SPR biosensor

Summary and Conclusions

• - Electronics and Photonics alone are insufficient technologies given the need for enhanced speed and precision of biosensing devices.

• - SPR technology is label-free and precise.• - SPR (Surface Plasmon Resonance) biosensing can be designed using

a variety of geometric and chemical specifications reflective of chemical compositions.

• - SPR technology may be further optimized for sensitivity and selectivity for specified wavelengths.

• - SPR technology can further optimize spatial organization on chips.

References & Acknowledgements• B. Wild et al. ACS Nano 6, 472 (2011).

• Bogaerts, W., Baets, R., & Bienstein, P. (2005, January). Nanophotonic waveguides in silicon-on-insulator fabricated with CMOS technology. Journal of Lightwave Technology, 23(1), 401-412.

• How does surface plasmon resonance work?. (2015). In Bionavis. Retrieved April 15, 2015, from http://www.bionavis.com/technology/spr/• Gaponenko, S. V. (2010). Introduction to nanophotonics (pp. 297-311). Cambridge: Cambridge University.• Khai Q. Le and P. Bienstman, Nanoplasmonic resonator for biosensing applications, 15 th Annual Symposium of the IEEE Photonics Benelux Chapter,

Deft, Netherlands (2010).• Khai Q. Le, B. Maes and P. Bienstman, Numerical study of plasmonic nanoparticles enhanced light emission in silicon light-emitting-diodes,

15th European Conference on Integrated Optics, United Kingdom (2010).• Sensor technology alert. distributed fiber sensor; surface plasmon resonance; wearable glucose sensor. (2006, December 1). In Frost & Sullivan.• Sun, Y., & Fan, X. (2010, June 6). Optical ring resonators for biochemical and chemical sensing. Anal. Bioanal Chemistry, 205-211. doi:10.1007/s00216-010-

4237-z• Powell, C. J., & Swan, J. B. (1959, March 30). Origin of the characteristic electron energy losses in aluminum. Physical Review Letters, 869.

doi:http://dx.doi.org/10.1103/PhysRev.115.869•R. M. Dickson et al. J. Phys. Chem. B 104, 6095 (2000).

•For additional insight into the formal Mathematics and Physics behind SPR, see nanoplasmonic-related articles by:

•Dr. P. Bienstman, Ghent University

•Dr. Polman, Amolf University

•Dr. Shalaev, Purdue University

•Dr. Peter Debackere, UC-Berkeley

Key Concepts

1. Why should we focus on plasmonic biosensing? Explain using proportionality analysis of electronics and photonics alone.

2. What is a plasmon?

3. Decribe, qualitatively, the electromagnetics behind surface plasmon resonance.

4. What two things make for a good biosensor?

5.How does a SPR Kretschmann-designed biosensor work?