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… $$
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?
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
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.
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?