Biometric Sensing:
Plasmonic Theory and Label-free
Applications
University of Minnesota-Duluth
EE4611: Semiconductor Physics and Devices
Joshua MacVey
Dr. 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 research
And, of course… $$
Strong Growth Predicted for Biosensors Market
Broad Categories:
Labeled vs label-free
Extreme Generality
What is labeling?
•
Attachment of a fluorescent marker to
biomolecule
+
•
=
measure signal under laser excitation
laser
signal
CAN WE THINK
OF ANY PROS
AND CONS TO
LABELING?
Label-free sensing
P
Example: Ring-resonator
ΔP

Δλ
Sun, et. al (2010)
1.55 μm
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?
+
+ +
Ne 2
Plasmons in the bulk oscillate at
p

m 0
determined by the free electron density and effective
mass
drude
Bulk plasmon
-
-
-
k
+
Surface plasmon
-
+
Metal
Localized
Surface plasmon
Prof. Polman’s nanophotonic course@Amolf
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
Surface plasmon
(or surface plasmon-polariton )
H
k
+
-
dielectric
E
+
Note: this is a TM wave
Localized Surface plasmon
Wavelength dependent local field
intensity
Plasmon propagation in micro-/nanowires
1µm
R. M. Dickson et al. J. Phys. Chem. B 104, 6095 (2000)
B. Wild et al. ACS Nano 6, 472 (2011)
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 biosensing
performance
1. Enhancing sensitivity
Δλ
Intensity
Intensity
Δλ
Wavelength
Wavelength
low sensitivity
high sensitivity
Approaches to enhance biosensing
performance
2. Enhancing selectivity
P
high Q-factor (high selectivity)
λ
Intensity
Δλ
P
FWHM
λ
Δλ
Sensitivity
Increases with increasing Q factor of the ring
Q
resonance/3dB
Wavelength
low Q-factor (low selectivity)
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 biochemistry
From source
To detector
Prism
R

Gold
Dr. Peter Debackere’s Internal tutorial
Configurations: How can we excite SPP Modes?
Otto Configuration
Fiber optics Sensors
Kretschman
Configuration
Resonant Mirror
Configuration
Waveguide
Integrated 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
657 nm
65.61˚
677 nm
65.71˚
Au thickness 44 nm, resonance angle 65.58 degrees, resonant wavelength 650 nm
Response Curves
• Angular Response
Spectral Response
1610 nm
22.73˚
1683 nm
22.75˚
Au-layer thickness 38 nm resonance angle 22.71 degrees resonance wavelength 1600
Sensitivity
BK 7 Glass Prism
Silicon Prism
Sensitivity [nm/RIU]
Wavelength shift [nm/RIU]
35000
30000
90000
spectral half width
spectral half width
300
250
200
150
100
50
0
440
85000
0.6
0.8
Wavelength shift [nm/RIU]
40000
Sensitivity [nm/RIU]
1
25000
20000
420
400
380
80000
360
340
1.53
1.58
1.63
1.68
75000
70000
65000
15000
Sensitivity total contribution
FRESN
Sensitivity total contribution
60000
10000
0.6
0.65
0.7
0.75
0.8
Wavelength [um]
0.85
0.9
0.95
1.5
1.55
1.6
Wavelength [um]
1.65
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
SPR sensing streptavidin binding to biotin
Ag
Δλ=12.7nm
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, 15th 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?