Nanophotonics: principle and application. Khai Q. Le Lecture 11 Optical biosensors

Nanophotonics: principle and application Khai Q. Le Lecture 11 Optical biosensors

Outline Biosensors: Introduction Optical Biosensors Label-Free Biosensor: Ringresonator Theory Measurements: Bulk sensing Measurements: Surface sensing Label-Free Biosensor: Surface Plasmon Biosensors Surface plasmon resonance biosensors Surface plasmon interference biosensors Localized surface plasmon resonance biosensors

Strong Growth Predicted for Biosensors Market

Why biosensors? measure biomolecules: Proteins DNA Cells applications in: Diagnostics Drug research Prof. Peter Bienstman s Internal tutorial

Labeled vs labelfree

What is labeling? attach fluorescent marker to biomolecule + = measure signal under laser excitation laser signaal Prof. Peter Bienstman s Internal tutorial

Label-free sensing P ΔP Δλ 1.55 μm Prof. Peter Bienstman s Internal tutorial

Labeling Pro: very sensitive (down to single molecule) Con: very ad-hoc expensive can disturb biological processes Prof. Peter Bienstman s Internal tutorial

Less sensitive Label-free but: prospective for more integration on chip Prof. Peter Bienstman s Internal tutorial

What makes a good sensor? Prof. Peter Bienstman s Internal tutorial

Bulk sensitivity nm/riu Prof. Peter Bienstman s Internal tutorial

Adlayer sensitivity (surface sensing) nm/nm (assume n known) Prof. Peter Bienstman s Internal tutorial

Sensitivity as defined here: purely optical parameter Prof. Peter Bienstman s Internal tutorial

Detection limit detection limit = noise / sensitivity e.g. bulk: 5 pm / (1 pm/riu) = 5 RIU Prof. Peter Bienstman s Internal tutorial

Detection limit surface sensing Concentration: ng/ml Surface coverage: pg/mm2 (calculation assumes homogeneous mixing, 100% coverage, ) Prof. Peter Bienstman s Internal tutorial

Intensity Intensity Approaches to enhance biosensing performance 1. Enhancing sensitivity Δλ Δλ Wavelength Wavelength low sensitivity high sensitivity

Intensit y Approaches to enhance biosensing performance 2. Enhancing selectivity P high Q-factor (high selectivity) P Δλ λ FWHM Δλ λ Wavelength low Q-factor (low selectivity)

Optical Label-free sensing Ring resonator (peak shift) Surface plasmons (peak shift) Surface plasmon resonances Surface plasmon interferences Localized surface plasmon resonances (nanosensor) Waveguide sensing (interferometry) Photonic Crystals Peak shift from defect Measure band gap change Interferometry

Biosensors Waveguide sensors :Microring Cavities Evanescent field sensing Technology and principle well understood Surface modification and biomolecule immobilisation are the biggest issues Surface Plasmon Sensor Sensing with surface plasmon modes Novel technology and principle Surface modification and biomolecule immobilisation well understood Dr. Peter Debackere s Internal tutorial

Incoupling Port Theory resonance n eff D m Drop Port Pass port flow with biomolecules microring cavity biosensor matching biomolecule (analyte) biorecognition element (ligand) functional monolayer Dr. Peter Debackere s Internal tutorial

Theory Intensity Measurement Mode Monochromatic Input, monitor output power as a function of refractive index P Advantage : real-time interaction registration Disadvantage : limited range Wavelength Interrogation Mode Broadband input, monitor resonance wavelength as a function of refractive index Advantage: easy to multiplex Disadvantage: slower detection method Dr. Peter Debackere s Internal tutorial Sensitivity Increases with increasing Q factor of the ring Q resonance 3 db P

Measurement Setup Light from tunable laser Flow Cell Light to photodetector SiO 2 Si Temperaturecontrol Results presented here: Static measurements : zero flow rate Flow cell dimensions Ø~2mm 2 Towards microfluidic setup: Continuous flow with syringe pump Flow cell dimensions Ø~100μm 2 Dr. Peter Debackere s Internal tutorial

Bulk refractive index sensing No surface chemistry involved Different salt concentrations Good repeatability (small variations around mean value) resonance wavelength shift [nm] 0.35 0.3 0.25 0.2 0.15 0.1 0.05 Sensitivity shift of 70nm/RIU λmin= 5pm n min =1*10-5 RIU 0 1.333 1.334 1.335 1.336 1.337 1.338 refractive index [RIU] Dr. Peter Debackere s Internal tutorial

Surface Sensing Biotin/Avidin biotin buffer ph7,4 resonator avidin concentration resonator buffer ph7,4 resonator avidin biotin 0.0045 0.004 0.0035 0.003 output [au] 0.0025 0.002 0.0015 0.001 0.0005 P λ 0 1551.80 1551.90 1552.00 1552.10 1552.20 1552.30 1552.40 1552.50 1552.60 wavelength [nm] Dr. Peter Debackere s Internal tutorial

Surface Sensing Biotin/Avidin resonance wavelength shift [nm] 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 5 10 15 20 25 avidin concentration [μg/ml] High avidin concentrations: saturation Low avidin concentrations: quantitative measurements λ min = 5pm 50ng/ml Dr. Peter Debackere s Internal tutorial

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 Prism To detector R Gold Dr. Peter Debackere s Internal tutorial

Theory Bulky surface plasmon biosensor Fully integrated lab-on-chip solution in Silicon-on-Insulator Dr. Peter Debackere s Internal tutorial

Configurations Otto Configuration Kretschman Configuration Resonant Mirror Configuration Fiber optics Sensors Waveguide Integrated SPR LSPR nanosensor

Otto : Design Which metal? Thickness of the Metal? Dr. Peter Debackere s Internal tutorial

Response Curves Angular Response Spectral Response Au thickness 44 nm, resonance angle 65.58 degrees, resonant wavelength 650 nm Dr. Peter Debackere s Internal tutorial

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 Dr. Peter Debackere s Internal tutorial

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 Dr. Peter Debackere s Internal tutorial

Sensitivity BK 7 Glass Prism Silicon Prism Sensitivity [nm/riu] Sensitivity [nm/riu] 40000 spectral half width 90000 spectral half width Wavelength shift [nm/riu] 35000 30000 25000 20000 300 250 200 150 100 50 0 0.6 0.8 1 Wavelength shift [nm/riu] 85000 80000 75000 70000 440 420 400 380 360 340 1.53 1.58 1.63 1.68 15000 10000 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 Wavelength [um] Sensitivity total contribution FRESNEL CAMFR 65000 Sensitivity total contribution 60000 1.5 1.55 1.6 1.65 Wavelength [um] Dr. Peter Debackere s Internal tutorial

Theory : Concept Surface Plasmon Interferometer Sample medium 5 μm Au Si SiO 2 Si 4 μm 1 μm.22μm 10 μm Dr. Peter Debackere s Internal tutorial

Simulation : Intensity Measurement Constructive Interference Dr. Peter Debackere s Internal tutorial

Simulation : Intensity Measurement Destructive Interference Dr. Peter Debackere s Internal tutorial

Simulation : Intensity Measurement Optimalisation of Design Si thickness = 160 nm Length = 10 m Si thickness = 100 nm Length = 6.055 m Dr. Peter Debackere s Internal tutorial

Simulation : Intensity Measurement Sensitivity Analysis 10-5 Change in the refractive 10-6 10-7 Sensitivity index that causes a drop or rise in the transmission of 0.01 db Dr. Peter Debackere s Internal tutorial

Simulation : Intensity Measurement Sensitivity Analysis 10-5 10-6 10-7 Comparison Prism Coupled SPR 1 x 10-6 Grating Coupled SPR 5 x 10-5 MZI SOI Sensors 7 x 10-6 Integrated SPR LIC 5 x 10-6 BUT Dimensions are two orders of magnitude smaller Dr. Peter Debackere s Internal tutorial

Simulation: Wavelength Interrogation Shift of the spectral minimum Shift of the spectral minimum as a function of the bulk refractive index Dr. Peter Debackere s Internal tutorial

Simulation: Wavelength Interrogation Sensitivity to adlayers For n=1.34 adlayer 6 pm/nm Dr. Peter Debackere s Internal tutorial

Measurement Setup Side View Top View Dr. Peter Debackere s Internal tutorial

Measurement Results Transmission (db) -18-20 -22-24 -26-28 -30 Transmission as a function of wavelength Measurement -16 1530 1540 1550 1560 1570 1580 1590 1600 1610 5 μm Au O2 toplayer Transmission [db] Compared to Theory Qualitative Agreement between experiment and theory Quantitative Need for a better fabrication process Transmission as a function of wavelength Simulation -11 1480 1500 1520 1540 1560 1580 1600-12 -13-14 -15-16 -17-32 Wavelength (nm) Dr. Peter Debackere s Internal tutorial -18 Wavelength [nm]

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

Localized surface plasmon resonance (LSPR) biosensor LSPR sensing streptavidin binding to biotin Ag Δλ=12.7nm Single nanoparticle LSPR biosensor