P09051 Low-Cost Oxygen Sensor Via Fluorescence Spectroscopy

Professor Slack Professor Rommel

Guide: Electrical Engineering Dept. Guide: Microelectronic Engineering Dept.

Mission StatementTo 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

BackgroundCommercial 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

Design Process

Simulate Support

Electronics in PSpice

Build and Test Support Electronics

Create Oxygen Sensing Film

Design Photodiode

Layout/Process

Fabricate in SMFL

Cleanroom

Package and Test

Prototype Sensor

Test Sensor In Flow Chamber

Generate Stern-Volmer Characteristic Plots for

Oxygen Quenching of Film

* 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

Fluorescence Spectroscopy System Outline

Project included the following design phases:I. Design and Build Support Electronics for LED and PhotodiodeII. Create Oxygen Sensing Thin FilmIII. Design and Fabricate Photodiode in the RIT Semiconductor and Microsystems

Fabrication Laboratory (SMFL)IV. Assemble Sensor PrototypeV. Test Prototype in Custom-Built Gas Flow ChamberVI. Gather Results to Generate a Stern-Volmer Characteristic Curve

Stern-Volmer Kinetic RelationshipApplies to the change in quantum yield of a photochemical reaction in the presence of a quenching element:

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)

Long-Pass Optical Filter Integration to Reduce LED to Photodiode Interference

Sensor WITHOUT Optical Filter Stray light from LED

Sensor WITH Optical Filter No Stray Light

Visible Fluorescence

Support Electronic Schematic Generation

Photodiode – Transimpedance Amplifier with Custom Signal Filtering

LED – Pulsing Circuit

Oxygen Quenching Phenomenon

Indicator Excited by 455nm λ

Indicator Emits Fluorescence

Oxygen Molecule Strikes Indicator

Energy TransferIndicator Oxygen

Indicator Ceases to Fluoresce, Decrease in Photonic Signal

Photodiode Assembly(S5973)

LED Assembly(455nm LED)

Assembled Support Electronics

Customer Specifications

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

Customer Needs

Samuel H Shin Jeremy V GoodmanElectrical Engineering Dept. Microelectronic Engineering Dept.

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