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  Antifouling coating for sensor transducers used for monitoring fluid propertiesUSPTO Application #: 20080107797Title: Antifouling coating for sensor transducers used for monitoring fluid properties Abstract: A coating for sensor transducers that transmit a signal to—and/or receive a signal from—a fluid, either liquid or gas, in contact with the transducer. In particular the coating minimizes or eliminates fouling of the transducer surface by the fluid, reducing the need for transducer maintenance, while not interfering with the transducer's ability to send and/or receive signals. (end of abstract) Agent: The Lubrizol Corporation Attn: Docket Clerk, Patent Dept. - Wickliffe, OH, US Inventors: Joseph W. Pialet, Carlos A. Piedrahita, William P. Taylor USPTO Applicaton #: 20080107797 - Class: 427 58 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080107797. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]The present invention relates to coatings for transducers in a sensor that contact a fluid, which is defined herein as a liquid, a gas or combinations thereof, to apply signals and/or measure responses when measuring a fluid property, wherein the fluid property can be a physical or chemical quality or condition. The invention finds application on transducer surfaces, which can be metal, semi-conductors, polymers, crystalline or amorphous materials or the like, that have, or can be functionalized to have, hydroxyl sites. The invention can be used with transducers for off-line, on-line or in-line monitoring and/or analysis of fluids such as, for example, lubricants, natural and/or synthetic motor oils, standard additives and/or adjuncts, combustion engine fuels, other hydrocarbon-based fluids used in transportation and industrial applications, and the like. More specifically, the present invention relates to antifouling coatings that do not substantially interfere with the transducer's ability to apply signals to and/or measure responses from a fluid, while reducing the need for transducer maintenance, such as cleaning. [0002]Fluids are a critical component for the proper operation of many types of devices and/or processes. For example lubricants are needed for an internal combustion engine to efficiently provide power over a long service life, metal working fluid is needed in machining equipment for rapid metal removal and maximum tool life, and vapors above liquid can be used to identify the liquid. Optimum performance is achieved when the fluid in question is of a proper quantity and quality for the application. For a particular application, a fluid preferably includes an appropriate base fluid and desired performance additives, e.g. corrosion inhibitors, friction modifiers, dispersants, surfactants, detergents, markers and the like. During use or consumption, a fluid's condition should remain within specified limits, that is, chemical and/or other fluid changes should be within proper performance specifications. [0003]A fluid's quantity, initial quality and/or continuing condition are often determined using sensors that test particular fluid properties. Such sensors, whether used off-line, on-line, or in-line, typically have one or more transducers contacting the fluid to transmit a signal, receive a response, or both transmit a signal and receive a response. A limitation for sensors is that the transducer can be fouled by the fluid, or components of the fluid including contaminants, being tested. To alleviate a fouling problem, sensors may require regular cleaning or replacement of the transducers, often after each fluid test, in order to provide sufficiently accurate results. Fouling problems can be particularly acute with sensors that make surface dependent measurements in fluids that are "surface active". For example, an attenuated total reflectance (ATR) infrared sensor, which uses an internal-reflectance-element (IRE) in contact with a fluid to determine fluid absorption at one or more frequencies, can show substantial signal drift in a lubricant formulated to provide surface corrosion and wear protection. [0004]While coatings, such as Teflon.RTM., are known to be used in some applications to protect transducers from fouling, an issue with present coatings is that they can substantially interfere with a signal being sent and/or received by the transducer, thereby limiting the performance of a sensor. Typical coatings have their own IR attenuation which limits their use in IR sensor applications, and many current coatings have electrical impedance or porosity issues which limit their use in sensors that transmit or receive electrical signals. Another issue with current coatings on sensor transducers is that the coating thickness is not easily controlled. Many coatings, with desirable properties, cannot be controllably applied in a sufficiently thin layer; for example, on an ATR infrared sensor's IRE transducer the coating must be on the order of nanometers to allow the optical signal to penetrate through the coating and into the fluid. Another problem with current sensor coatings is that the coatings do not provide adequate fouling protection for the transducer. That is, the coating does not substantially decrease transducer maintenance. Therefore, there is need for an improved transducer coating that does not substantially interfere with the operation of a sensor and that provides an increased transducer maintenance-free operating period. [0005]The present invention overcomes limitations of previous coatings for transducers used to monitor/analyze fluids. The invention is a simple, cost-effective coating that has minimal effect on signals being sent and/or received by transducers in contact with a fluid, that can be applied in a controlled thickness, and that substantially decreases or eliminates transducer fouling thereby increasing the transducer's maintenance-free operating period. BRIEF DESCRIPTION OF THE DRAWINGS [0006]FIG. 1 is a graph showing test results for an ATR infrared sensor having an IRE transducer that does not have a coating of this invention. [0007]FIG. 2 is a graph showing test results for an ATR infrared sensor having an IRE transducer that does have a coating of this invention. SUMMARY OF THE INVENTION [0008]The present invention is a coating for sensor transducers that are used in the measurement of a fluid property. The coating on the sensor transducer comprises at least one of an alkoxysilane, a chloro-terminated-silicone-oligomer or combinations thereof, which either may have non-hydrolysable side-chains and/or repeat-groups selected to minimize or eliminate reaction with--or wetting by--fluids or fluid components in contact with the transducer while in use, and to minimize or eliminate absorption or blocking of signals between the transducer and the fluid in contact with the transducer when in use. [0009]A feature of the invention is that the coating can contain molecules with at least one reactive site bonded to the transducer surface and no molecule-molecule bonding, (no cross-linking or chain extension), molecules with at least one reactive site bonded to the transducer surface and molecule-molecule bonding, molecules bonded to surface-bonded molecules which are also bonded to the surface, or combinations thereof. [0010]The invention is further a process to coat a sensor transducer, comprising: [0011]a) cleaning the transducer surface, [0012]b) immersing the transducer into a solution selected from the group consisting of alkoxysilanes in an aqueous hydrocarbon-solvent solution, chloro-terminated-silicone-oligomers in a dry hydrocarbon solvent or combination thereof, [0013]c) rinsing the transducer with solvent, and [0014]d) drying the transducer, wherein such coated sensor transducer is used to measure/analyze fluid quality/condition. [0015]A feature of the invention is that cleaning the transducer surface can simply remove contaminants from the surface that would interfere with an alkoxysilane or a chloro-terminated-silicone-oligomer reacting with hydroxyl sites on the transducer surface or combination thereof. [0016]Another feature of the invention is that cleaning of the transducer surface can include functionalizing the surface by oxidation, hydrolysis or hydration to increase the number of hydroxyl sites on the transducer surface. [0017]Another feature of the invention is that the porosity and thickness of the transducer coating can be varied by varying the number of hydroxyl sites on the transducer surface. [0018]In an embodiment of the invention the alkoxysilanes in the solution are selected from the group consisting of monoalkoxysilanes, dialkoxysilanes, trialkoxysilanes, bis-alkoxysilanes or combinations there of. [0019]In another embodiment of the invention the alkoxysilanes in the solution can have at least one substituent of the silicon which is an alkyl or aryl group which may optionally contain groups such as, but not limited to, fluorine, chlorine or the like. [0020]In another embodiment of the invention the aqueous-hydrocarbon solvent in an alkoxysilane solution for immersing a transducer can be an aqueous acidic alcohol solution. Continue reading... Full patent description for Antifouling coating for sensor transducers used for monitoring fluid properties Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Antifouling coating for sensor transducers used for monitoring fluid properties patent application. Patent Applications in related categories: 20080171134 - Integrated capacitive microfluidic sensors method and apparatus - A microfluidic device and method for capacitive sensing. 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