Fiber-optic Sensors for the Monitoring of Liquid Mixtures Optical Engineering, Feb. 26, 2014 Eyal Preter, 1 Vlada Artal, 1,2 Chaim N. Sukenik, 2 and Avi Zadok 1,* 1 Faculty of Engineering, Bar-Ilan University, Israel 2 Departmaent of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Israel

How to monitor Evaporation? Traditionally:  Direct observation: contact angle Goniometer  AFM cantilevers  Micro Gravimetry Accuracy Complicated Setup Limited accessibility 2 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Objective Simple, low-cost fiber-optic sensor for monitoring the evaporation of liquids Proof of concept Evaporation-related data Comparing with traditional methods Applications 3 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

The Setup Laser Fiber Tip Resonator Circulator Power Meter Scope The Sensor: Cleaved Fiber The Input: Fixed Laser Source The Readout: Low Bandwidth Detector & Scope. 4 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Principle of Operation Light is launched from the remote end of the fiber, and the reflected power is monitored Light is reflected at the fiber / liquid interface, and the liquid / air interface The two reflections combined create interference, according to the thickness of the liquid droplet As the liquid evaporates, interference fringes are observed: 5 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Typical Results: Raw Data Water 6 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Typical Results: Instantaneous Droplet Length Water 7 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Control Experiment 8 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Control Experiment 9 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Apps (1): Mixtures Study Ethanol Concentration In Water 10 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Apps (1): Mixtures Study Ethanol Concentration In Water 11 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Apps (2): Recognition of solvents: bare fiber tip Difficult to categorize 10 solvents based on evaporation time and droplet size alone 12 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Surface Modification Surface treatment  Deposition of single layer (monolayer) hydrophobic coating.  The monolayer does not interact with the light, but changes the surface behave. Normal Fiber Coated Fiber 13 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Surface Modification Dynamics Bare Fiber Coated Fiber 14 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Evaporation from modified surfaces Acetone 15 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Droplet length on coated fiber: relation with polarity index 16 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Apps (2): Recognition of solvents: coated fiber tip Evaporation from coated fibers can distinguish between all 10 solvents through simple data analysis 17 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Apps (2): Recognition of solvents: combined analysis Solvents recognition based on the combined analysis of evaporation from both bare and coated fibers 18 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Apps (3): Recognition of flexible fuel blends 19 A Flex Fuel Sensor is a device that measures the ethanol content in the car’s fuel system. The sensor is installed between the fuel pressure regulator and the fuel tank, where it monitors the ethanol content of the fuel returning to the tank. The information is then passed onto the system which applies fuel, ignition and boost corrections. The system allows the driver to add any mixture of ethanol/petrol (from 0-100% ethanol content). Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Apps (3): Recognition of flexible fuel blends A large number of flexible-fuel vehicles in the US are equipped with an in-line sensor for reading the contents of alcohol in volume Sensors cost above 100$. The proposed fiber sensor is capable of recognizing different blends of ethanol-gasoline or methanol-gasoline 20 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Apps (3): Recognition of flexible fuel blends Methanol concentration in gasoline: 21 The sensor readout for each blend is different Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Potential Applications Identifying flexible fuel blends Detection of fuel fraud and dilution, at the gas station and inside the car Monitoring the production of bio-diesel (for example, using methanol and micro-waves) Monitoring the efficiency of internal combustion process, reduce pollution Quality control of water, beverages and food Mobile point-of-care diagnostics (NUFAR program, to begin March 2014). 22 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014

Conclusion 23 Dr. Avi Zadok, Bar-Ilan Univ. Feb. 2014