P09051
Low-Cost Oxygen Sensor Via Fluorescence Spectroscopy
Samuel H Shin
Jeremy V Goodman
Electrical Engineering Dept.
Microelectronic Engineering Dept.
Professor Slack
Professor Rommel
Guide: Electrical Engineering Dept.
Guide: Microelectronic Engineering Dept.
Mission Statement
To design, build, and test a low-cost oxygen sensor by taking advantage of the fluorescent properties of Tris-Ruthenium(II)
Dichloride-based compounds. Device uses a custom-made sensing film of Tris(2,2’-bipyridal)Dichlororuthenium(II) as the oxygen
indicator with a Philips LumiLED high-power LED as the excitation source and a Hamamatsu PIN Photodiode as a receiver.
Motivation
• Most fluorescent spectroscopy systems are accurate, but expensive
• Fluorescent oxygen sensors are in demand in industrial, environmental, and biomedical applications
Background
Commercial sensors are available that utilize the fluorescence spectroscopic technique of oxygen measurement. The versatility of
the technique enables its use in sensing volumes ranging from micro-scale and larger, all depending on the size of the sensing thin
film.
Requirements
• Cost-effective method of measuring molecular oxygen concentration in a gaseous environment
- Use low-cost electronics and materials which still provide for accurate results
• Provide consistent results during life of the sensor
Customer Needs
Fluorescence Spectroscopy System Outline
Customer Specifications
Design Process
Project included the following design phases:
I.
Design and Build Support Electronics for LED and Photodiode
II.
Create Oxygen Sensing Thin Film
III. Design and Fabricate Photodiode in the RIT Semiconductor and Microsystems
Fabrication Laboratory (SMFL)
IV. Assemble Sensor Prototype
V.
Test Prototype in Custom-Built Gas Flow Chamber
VI. Gather Results to Generate a Stern-Volmer Characteristic Curve
Main Requirements:
• High power LED with an emission wavelength of 455nm (max absorption into sensor thin film)
• Large photocurrent response from photodiode to increase Signal-to-Noise Ratio
• Fast response time of photodiode will lead to more precise fluorescent lifetime measurements
Support Electronic Schematic Generation
V2
5v dc
0
Design
Photodiode
Layout/Process
Simulate
Support
Electronics in
PSpice
M1
MbreakP
V
V1 = 5
V2 = 1
TD = 0
TR = 5n
TF = 5n
PW = 1m
PER = 10m
Create Oxygen
Sensing Film
Prototype Sensor
R1
2.6
0
V
D1N4149
D1
Fabricate in
SMFL
Cleanroom
Build and
Test Support
Electronics
V1
I
0
Photodiode – Transimpedance Amplifier with
Custom Signal Filtering
Package
and Test
LED – Pulsing Circuit
Assembled Support Electronics
Test Sensor In
Flow Chamber
Generate Stern-Volmer
Characteristic Plots for
Oxygen Quenching of Film
Photodiode Assembly
(S5973)
Stern-Volmer Kinetic Relationship
Applies to the change in quantum yield of a photochemical reaction in the
presence of a quenching element:
LED Assembly
(455nm LED)
Long-Pass Optical Filter Integration to Reduce LED to Photodiode Interference
Φ0/ Φ = Normalized Fluorescence Intensity (Recorded by Photodiode)
Φ0 = Measured Intensity in Absence of Oxygen
Φ = Measured Intensity in Presence of Oxygen
[Q] = Concentration of Elemental Quencher (Oxygen)
ksv = Stern-Volmer Constant (Quenching Efficiency of Sensor)
Oxygen Quenching Phenomenon
Indicator Excited by
455nm λ
Indicator Emits
Fluorescence
Oxygen Molecule
Strikes Indicator
Energy Transfer
Indicator  Oxygen
Sensor WITHOUT Optical Filter
Stray light from LED
Sensor WITH Optical Filter
No Stray Light
Visible Fluorescence
Indicator Ceases to Fluoresce, Decrease in Photonic Signal
* Special thanks to Jayadevan Radhakrishnan, Dr Robert Pearson, the RIT EE and μE departments, Dr Christopher Collison, Rich Deneen, Hamamatsu Photonics, Philips LumiLEDs, the RIT SMFL