Interferometric optical biosensor Xingwei Wang 1
Light Transverse electromagnetic wave Reflection Refraction Diffraction Interference 2
Fabry-Perot interferometer 3
Interferometer Two waves that coincide with the same phase will add to each other Two waves that have opposite phases will cancel each other out, assuming both have the same amplitude http://en.wikipedia.org/wiki/interferometer 4
Constructive and destructive interference http://en.wikipedia.org/wiki/interference 5
Michelson Interferometer http://en.wikipedia.org/wiki/interferometer 6
Constructive and destructive condition If these two paths differ by a whole number (including 0) of wavelengths, there is constructive interference and a strong signal at the detector. If they differ by a whole number and a half wavelengths (e.g., 0.5, 1.5, 2.5...) there is destructive interference and a weak signal. Violate conservation of energy? 7
Mach-Zehnder interferometer http://en.wikipedia.org/wiki/interferometer 8
How it works? A slight tilt of one of the beam splitters will result in a path difference and a change in the interference pattern. Can be very difficult to align. Very sensitive. 9
Advantages: very sensitive Coherent interferometry uses a coherent light source (for example, a helium-neon laser), and can make interference with large difference between the interferometer path length delays. The interference is capable of very accurate (nanometer) measurement by recovering the phase. 10
Problem Coherent interferometry suffers from a 2π ambiguity problem If between any two measurements the interferometric phase jumps by more than 2π the phase measurement is incorrect Dynamic range 11
Solution Combining interferometry results obtained using multiple wavelengths of illumination Ambiguity interval can be extended to indefinitely large dynamic ranges of measurement 12
Mach Zehnder interferometers (MZIs) for biosensing Long (typically 9 20 mm) evanescentwave/biomaterial interaction paths Required length for a detectable cumulative effect when using a single pass of light through the sensing arm 13
EFPI The required sensing length may be reduced by having the light double back through multiple reflections along its propagation path. The use of a single-cavity extrinsic Fabry Pérot interferometer (EFPI) as a guidedwave/bulk-biomaterial interaction biosensor. J. L. Elster, M. E. Jones, M. K. Evans, S. M. Lenahan, C. A. Boyce, W. Velander, and R. VanTassell, Optical fiber extrinsic Fabry Pérot interferometric (EFPI)-based biosensors, SPIE, vol. 3911, pp. 105 112,2000. 14
Schematic diagram of a PSW-FPI integrated in a umz structure 15
Schematic view of experiment setup 16
Huygen's principle 17
Diffraction 18
Single slit diffraction 19
Analysis Huygen's principle Each part of the slit can be thought of as an emitter of waves. All these waves interfere to produce the diffraction pattern. 20
Results Destructive interference: 1-5; 2-6; 3-7; 4-8 Half a wavelength out of phase (w/2)sinθ = λ/2 or wsinθ = λ Other dark fringes in the diffraction pattern produced are found at angles θ for which wsinθ = mλ If the interference pattern is viewed on a screen a distance L from the slits, then the wavelength can be found from the spacing of the fringes. λ = zw/(ml) 21
Diffraction grating Identical, equally-space slits? The bright fringes, which come from constructive interference of the light waves from different slits, are found at the same angles they are found if there are only two slits. But the pattern is much sharper. Why? 22
Diffraction grating Each scattering center acts as a point source of spherical wavefronts; These wavefronts undergo constructive interference to form a number of diffracted beams. Many positions of completely destructive interference between the bright, constructiveinterference fringes. 23
Colorimetric resonant reflection as a direct biochemical assay technique A guided mode resonance filter that, when illuminated with white light, is designed to reflect only a narrow band of wavelengths where the reflected wavelength is tuned by the adsorption of biological material onto the sensor surface. 24
Label-free Common labels radioisotopes, fluorophores, enzyme substrates. Label-free removes experimental uncertainty induced by the effect of the label on molecular conformation, blocking of active binding epitopes, steric hindrance, inaccessibility of the labeling site, or the inability to find an appropriate label that functions equivalently for all molecules in an experiment. Label-free detection methods greatly simplify the time and effort required for assay development, Removing experimental artifacts from quenching, shelf life, and background fluorescence. 25
Key technology - grating A narrow bandwidth guided mode resonant filter structure a sub-wavelength grating structure produces a particular diffraction anomaly providing a surface that, when illuminated with white light at normal incidence, reflects only a very narrow (resonant) band of wavelengths. The resonantly reflected wavelength is shifted by the attachment of biomolecules to the guided mode filter, small changes in surface optical density can be quantified Equivalent sensor structures have been fabricated onto glass substrates and incorporated into sheets of plastic film. Incorporation of the sensor into large area disposable assay formats such as microtiter plates and microarray slides. 26
Sensitivity Protein-protein Detection of antibody with 8.3 nm sensitivity Low non-specific binding 27
Schematic diagram 28
Reflectivity response 29
Computer simulation of spectral shift due to the binding of molecules 30
Computer simulation results 31
Reading system 32
Schematic diagram of the array 33
SEM picture of the grating 34
Reading system 35
Measured shifting of the resonant wavelength with binding of molecules 36
Peak wavelength shift 37
Test 38
Imaging To produce images of bound biomolecule patterns as applied by a microarray spotter An instrument is used to acquire spatial maps of the resonant reflected wavelength 39
Applications The biosensor imaging capability is expected to yield applications in pharmaceutical compound screening, genomics, proteomics, and molecular diagnostics, where there is a need to screen large numbers of biochemical interactions against samples using low volumes of reagents. 40
Parallel detection with an array The ability to detect the interactions between sets of DNA probes arrayed on to glass surfaces and test samples are used for genotyping, gene expression analysis, and gene sequencing. Likewise, arrays of hybridized protein probes are finding applications in protein pathway analysis, and protein expression diagnostic tests. The concept of parallel detection of sample interaction with an array of hybridized probes is further expanding into Small molecule screening for pharmaceutical discovery Environmental testing, and others. 41
Schematic diagram for imaging 42
VCSEL laser and PIN detectors 43
System setup 44
Dynamic measurements 45
Static measurements 46
Comparison results with white light and laser 47
Advantages Low cost Multi-analyte analysis in parallel Simple setup no coupling prisms No electricity wiring 48
References Optical fiber extrinsic Fabry Pérot interferometric (EFPI)-based biosensors J. L. Elster, M. E. Jones, M. K. Evans, S. M. Lenahan, C. A. Boyce, W. Velander, and R. VanTassell SPIE, vol. 3911, pp. 105 112,2000. Investigation of a Periodically Segmented Waveguide Fabry PÉrot Interferometer for Use as a Chemical/Biosensor N Kinrot, M Nathan Journal of Lightwave Technology, Volume 24, Number 5 (May 2006) Page Numbers: 2139-2145 Label-free optical technique for detecting small molecule interactions Bo Lin, Jean Qiu, John Gerstenmeier, Peter Li, Homer Pien, Jane Pepper and Brian Cunningham Biosensors and Bioelectronics, Volume 17, Issue 9, September 2002, Pages 827-834 49
References A new method for label-free imaging of biomolecular interactions Li, P.Y.; Bo Lin; Gerstenmaier, J.; Cunningham, B.T.; Sensors, 2003. Proceedings of IEEE Volume 1, 22-24 Oct. 2003 Page(s):310-315 Vol.1 Digital Object Identifier 10.1109/ICSENS.2003.1278948 A plastic colorimetric resonant optical biosensor for multiparallel detection of label-free biochemical interactions Cunningham, B.; Qiu, J.; Lin, B.; Li, P.; Pepper, J.; Sensors, 2002. Proceedings of IEEE Volume 1, 12-14 June 2002 Page(s):212-216 vol.1 Digital Object Identifier 10.1109/ICSENS.2002.1037084 Colorimetric resonant reflection as a direct biochemical assay technique Brian Cunningham, Peter Li, Bo Lin and Jane Pepper Sensors and Actuators B: Chemical, Volume 81, Issues 2-3, 5 January 2002, Pages 316-328 50