Constraint Based Modeling Geometric and Dimensional ENGR 1182 SolidWorks 03.
Engr 1182.03 College of Engineering Engineering Education Innovation Center Engr 1182 Nano Pre-Lab...
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Transcript of Engr 1182.03 College of Engineering Engineering Education Innovation Center Engr 1182 Nano Pre-Lab...
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Engr 1182.03
Presentation Short Title 1
College of EngineeringEngineering Education Innovation Center
Engr 1182 Nano Pre-Lab
Detection Circuit 2
Rev: 20XXMMDD, Initials
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Engr 1182.03
Presentation Short Title 2
Wavelengths vs. Features Size
Rev: 20XXMMDD, Initials
The wavelength of a sinusoidal wave is the spatial period of the wave— the distance over which the wave's shape repeats. The smaller the wavelength of the wave the higher the energy of the wave.
100 10 10-2 10-4 10-6 10-8 10-10 10-12 Wavelength in meters
Nanotechnology
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Engr 1182.03
Presentation Short Title 3
Fluorescein Detection
Rev: 20XXMMDD, Initials photodetectorblue LED
Acrylic chipdetection well
emis
sio
n
excitation
Looking at a side view where Acrylic chipis sitting on top of the DAD
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Engr 1182.03
Presentation Short Title 4
Absorption of Light
Rev: 20XXMMDD, Initials
• Light of energy hnex is absorbed and excites an electron from E0 to E1 or to a higher energy level.
hnex Electronic Energy Levels
E1
E0
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Engr 1182.03
Presentation Short Title 5
Relaxation and Emission
Rev: 20XXMMDD, Initials
• Excited electron "relaxes" to the E1 state and then gets back to E0 by “emission” (releasing) of energy– E1-E0 =hnem< hne
• This energy of emission is in the form of light.
E0
E1
hnem Electronic Energy Levels
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Engr 1182.03
Presentation Short Title 6
Fluorescein
Rev: 20XXMMDD, Initials
Emission will ALWAYS be at a longer wavelength than the excitation.
Blue spectrum
Green spectrum
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Engr 1182.03
Presentation Short Title 7
Signal to Noise Ratio (SNR)• In any sensor circuit we must be concerned with detecting
unwanted signals which would invalidate our measurements.• These unwanted signals are called “noise.”• A figure of merit of a sensor circuit design is the relative
strength of true signal divided by unwanted signal detected: signal-to-noise ratio.
• The higher the SNR the better the performance of the sensor circuit we have.
Rev: 20XXMMDD, Initials
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Engr 1182.03
Presentation Short Title 8
Optical Considerations for SNR• Alignment of the LED and detector is very
important for a high quality sensor circuit.• Reflection off internal surfaces needs to be
minimized• Outside excitation sources must be shielded
from the photodetector.
Rev: 20XXMMDD, Initials
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Engr 1182.03
Presentation Short Title 9
Detection Alignment Device (DAD)
Rev: 20XXMMDD, Initials
DetectorSlot LED
Chamber
Chip HolderAlignment
Holes
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Engr 1182.03
Presentation Short Title 10
SNR: LED / Detector alignment• A critical angle of blue LED is chosen such that it maximizes the
exposure of detection well to the blue LED excitation so that photodetector senses green emission from the fluorescein in the detection well only.
Rev: 20XXMMDD, Initials
Plexiglass
PlexiglassPDMS Detection well
Detector aperture
LED
ReflectedLight
DADAcrylic
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Engr 1182.03
Presentation Short Title 11
SNR: Reflections from internal surfaces
• Since we have a stacked layer of materials to assemble our LOC, surface of the each layer can act as a reflecting surface.
• Reflections occur at those surfaces and they erroneously increase the signal seen by the detector.
• Those reflections can be minimized by no air pockets between surfaces(layers).
• Detection well should be fully filled with fluorescein so that no air gaps remain.
• Keep surfaces clean and smooth to avoid reflections.
Rev: 20XXMMDD, Initials
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Engr 1182.03
Presentation Short Title 12
SNR:Outside excitation sources• We are interested in only the signal from the direct
emission of fluorescein.• Room light contains all wavelengths and will create
significant error.• Notice the DAD uses a lot of black.• Black absorbs light and reduces reflection
Rev: 20XXMMDD, Initials