The present invention relates generally to antifouling systems and, more specifically, to antifouling systems operating in situ with an LED light source.
The growth and feeding of biofouling organisms (e.g., forming a hard substrate community) inhibits the operational characteristics of industrial objects, such as lenses. Several approaches are used to address this problem, including using coatings. However, in many circumstances a coating will not work. For example, windows of a submerged precision optical instrument cannot be coated due to concerns with obstructing the clarity of the windows, thereby affecting the instrument's measurements. Another approach is to remove the organisms manually, e.g., by scrubbing wiping akin to a windshield wiper, but the use of mechanical components can increase the opportunities for failure and introduce additional complexity and cost into the system.
Maintaining an uncompromised visual connection through the window is particularly important in many communications systems. For example, scientists are deploying unmanned underwater vehicles (UUV) that, due to their mobility, can expand the reach of seafloor observatories. These UUVs typically carry sensors on-board and operate autonomously, carrying out pre-programmed missions. While certain types of UUVs are tethered by cable to the seafloor observatories, the tethered UUVs have a short range of motion and are limited by the length of the tether. Scientists are also deploying un-tethered UUVs which may be controlled wirelessly by an acoustic communication system or an optical communication system. Acoustic communication systems, however, tend to be limited by low bandwidth and high latency, and do not permit video or other high-rate data transfers.
Accordingly, there is a need to provide an antifouling device that prevents and/or removes organisms from a surface in a marine environment. There is also a need for such a device to remove the organisms from a window while maintaining the integrity of the window for accurate sensor readings and communications.
The present invention relates to systems and methods for reducing fouling of a surface of an optically transparent element with a light source. By using LEDs, such a system may be more efficient, have a longer lifetime, and be more compact than traditional systems. The systems and methods may be further augmented by varying wavelengths and duty cycle.
According to one aspect, the invention relates to a system for reducing fouling of a surface of an optically transparent element subjected to a marine environment. The system includes an LED for emitting UV-C radiation, a mount for directing emitted UV-C radiation toward the optically transparent element, and control circuitry for driving the LED.
In accordance with one embodiment of the above aspect, the optically transparent element is a window or a lens. The emitted UV-C radiation may have a wavelength between about 265 nm and about 295 nm. The mount may be disposed on a side of the optically transparent element proximate the surface. The LED may be disposed in a watertight enclosure, which may have a UV transparent port. In other embodiments, the mount may be disposed on a side of the optically transparent element remote from the surface, and the optically transparent element may be made of a UV transparent material. In additional embodiments, the control circuitry is adapted to maintain a constant duty cycle of the LED, which may be at least about 10%. An attenuated dosage reaching the surface may be at least about 0.5 kJ/m2. A kill efficiency at the surface may be at least about 95%.
In another aspect, the invention relates to a method for reducing fouling of a surface of an optically transparent element subjected to a marine environment. The method includes providing an LED source for emitting UV-C radiation, driving the LED source to emit UV-C radiation, and directing emitted UV-C radiation toward the optically transparent element.
In accordance with one embodiment of the foregoing aspect, the optically transparent element is a window or a lens. The emitted UV-C radiation may have a wavelength between about 265 nm and about 295 nm. In some embodiments, the emitted UV-C radiation is directed on a side of the optically transparent element proximate the surface. The LED may be disposed in a watertight enclosure, which may have a UV transparent port. In other embodiments, the emitted UV-C radiation is directed on a side of the optically transparent element remote from the surface. The optically transparent element may be made of a UV transparent material. The LED may be driven to maintain a constant duty cycle, which may be at least about 10%. In additional embodiments, an attenuated dosage reaching the surface is at least about 0.5 kJ/m2. A kill efficiency at the surface may be at least about 95%.
Other features and advantages of the present invention, as well as the invention itself, can be more fully understood from the following description of the various embodiments, when read together with the accompanying drawings, in which:
The invention may be better understood by reference to the following detailed description, taken in conjunction with the figures. Various embodiments of the invention relate to a system for eliminating biofilm on a surface. Other configurations and variants will be apparent to those skilled in the art from the teachings herein.
The optically transparent element 102 may be located on an end cap 104 of the optical modem 100. The optically transparent element 102 can take many different forms, including a window or a lens (e.g., flat or curved). The end cap 104 may include one or more mounts 106 extending from an upper side thereof. These mounts 106 may be disposed near the periphery of the end cap 104, as depicted in
In certain embodiments, LEDs 110 may be mounted on an interior of the optically transparent element 102, remote from the surface to be irradiated, requiring any light intended to reach the surface to first pass through the material of the optically transparent element 102. To allow UV radiation to reach the surface, the optically transparent element 102 may be made of a UV transparent material. The interior LEDs 110 may be used alone or in conjunction with the exterior LEDs 108.
The LEDs 108, 110 may be controlled by a timer/driver circuit 201, as depicted in
A light emitting array 112 may be used to communicate with another optical device. In some embodiments, the array may be a receiver instead of, or in addition to, being an emitter, and may replace the light emitting array 112 referred to throughout the specification. The various embodiments of the array may be used for transmitting or receiving optical signals. The electronics controlling the LEDs 108, 110 and/or the electronics controlling the light emitting array 112 may be located on a mounting flange 114 extending from a lower side of the end cap 104. The mounting flange 114 may be protected from the exterior environment by a housing 116 and an additional end cap 118. Each of the end caps 104, 118 may have a bore 120, 122 respectively formed therethrough to provide passage into the optical modem 100, such as for electrical wiring, as depicted in
To use the system 101, the user may pre-program a control circuit 201 to drive the LEDs 108, 110 to emit UV-C radiation. This may be done on a set schedule, as part of a constant duty cycle, or on demand. When an appropriate amount and type of UV-C radiation is directed toward the optically transparent element 102, biofilm formed thereon is removed.
The experimental setup 301 includes an LED 308 (one 265 nm LED and one 295 nm LED in separate assemblies), a housing 316 with a window 304 for the LED 308 to project through, and a substrate 330 mounted to the housing with connectors 332. Also included, but not depicted, are a timer circuit, a current driver circuit, a power supply, underwater cable connectors, Subconn MCIL2M connectors, general radio connectors, and 5″×8″ enclosures.
The common timer circuit was programmed to a predetermined duty cycle (i.e., 80 minutes on, 12 hours off). The housings 316, one containing a 265 nm LED and the other a 295 nm LED (both with individual driver circuits), were sealed by screwing on their respective Lexan™ substrates 330a, 330b (SABIC Innovative Plastics; Pittsfield, Mass.). The housings 316 were then connected to their respective cables, and dangled underwater approximately 1 m below the low-tide line for optimal sunlight and constant submersion. The cables were then connected to the LED timer circuit, powered by a 12V DC power supply. The date and time were noted, and the substrates 330a, 330b were left to be fouled. Every few days, the housings 316 were recovered and the substrates 330a, 330b were removed without disturbing any potential growth. The underside of each substrate 330a, 330b was then studied for signs of growth and photographed (see
The first test configuration, with a duty cycle of 20 min on and 12 hr off (2.5%), was insufficient for antifouling purposes. Growth on both substrates 330a, 330b was reduced within the irradiated radii, but not completely. After two weeks, barnacles had appeared on the windows 304 of both housings 316, a clear sign of inadequate dosage.
The second test configuration, with a duty cycle doubled to 40 min on and 12 hr off (5%), yielded interesting results. While the substrate 330a radiated with 265 nm UV showed little improvement with the doubling of dosages, the more powerful yet less effective 295 nm LED 308 was much more successful. A slight biofilm did form on the 295 nm substrate 330b within its irradiated radius, but it was clearly more effective than the 265 nm, lower-power LED 308. Neither window 304 supported any kind of growth.
A third test configuration, as indicated in Table 1, was configured with a duty cycle of 80 min on and 12 hr off (10%). This time, both substrates 330a, 330b were kept completely clear of fouling, and there was no discernible difference between the effects of the two wavelengths of LEDs 308.
Based on the results of this experiment, one 295 nm UV LED 308 appears to perform just as well or better than a 265 nm UV LED 308 on the same duty cycle, and is therefore more cost effective, as 265 nm LEDs 308 typically cost more than 295 nm LEDs 308 (e.g., $229 for 265 nm, $149 for 295 nm). Dosages of 265 nm UV for antifouling may start at 1.37 kJ/m2, and for 295 nm UV may start at 2.29 KJ/m2. These dosages may provide a starting point which a user may back off to a threshold dosage, or may be increased by a user to provide a safety factor in irradiation.
To properly ensure transmission of shortwave UV, a specialty UV transparent window 304 may be used. For wavelengths in the 250-300 nm range, quartz and fused-silica may be suitable material choices. If an internal cleaning system is desired to prevent fouling on a window 304, the window should be designed for such an application to ensure UV reaches the surface at risk of biofouling. Alternatively, the antifouling system may be external and self-contained. Consideration may also be given to the fact shortwave UV may be subject to high attenuation losses in typical ocean waters, which somewhat limits the distances from the LED to its target substrate for which the LED can be effective.
For this experiment, the shortest possible path length (approximately 1.7 cm) of UV through water was chosen to minimize attenuation losses. While the attenuation coefficients for this range of UV in the waters at the test location were not known, a worst-case scenario estimate with a theoretical coefficient of 0.36 showed that the attenuated dosage to the 265 nm substrate would have been 0.49 kJ/m2 for the 80 min duty cycle. This may explain why the lower-duty cycles did not appear to be effective; the dosage required to kill 98% of microbes is 0.5 kJ/m2. However, in a different environment, the lower-duty cycles may be sufficient.
The experiment results suggest that both 265 nm and 295 nm UV LEDs 308 may be effective for antifouling purposes. As 295 nm LEDs tend to be less expensive and equally effective, they may be a preferred choice for the tested duty cycle. It is expected that experimentation with different wavelengths may produce different results. For example, a threshold dosage determined by reducing the UV dosage until one wavelength outperforms the other may be tested at different frequencies to develop a more versatile system that administers less obtrusive, seconds-long dosages at a higher rate. A decrease in off time would allow for lower dosages, decreasing the time for biofilms to accumulate between doses.
Various embodiments and features of the present invention have been described in detail with particularity. The utilities thereof can be appreciated by those skilled in the art. It should be emphasized that the above-described embodiments of the present invention merely describe certain examples implementing the invention, including the best mode, in order to set forth a clear understanding of the principles of the invention. Numerous changes, variations, and modifications can be made to the embodiments described herein and the underlying concepts, without departing from the spirit and scope of the principles of the invention. All such variations and modifications are intended to be included within the scope of the present invention, as set forth herein. The scope of the present invention is to be defined by the claims, rather than limited by the forgoing description of various preferred and alternative embodiments. Accordingly, what is desired to be secured by Letters Patent is the invention as defined and differentiated in the claims, and all equivalents.
This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 61/671,426 filed on Jul. 13, 2012, the disclosure of which is hereby incorporated herein by reference in its entirety.
Federal funds awarded by the National Science Foundation under Grant Nos. OCE-0942835 and OCE-0737958 contributed to making this invention. The U.S. Government has certain rights herein.
Number | Name | Date | Kind |
---|---|---|---|
3418138 | Dennis et al. | Dec 1968 | A |
3500041 | Kassing | Mar 1970 | A |
4297222 | Takeguchi et al. | Oct 1981 | A |
4320085 | Takeguchi et al. | Mar 1982 | A |
5308505 | Titus et al. | May 1994 | A |
5322569 | Titus et al. | Jun 1994 | A |
5660719 | Kurtz et al. | Aug 1997 | A |
6475433 | McGeorge et al. | Nov 2002 | B2 |
6483119 | Baus | Nov 2002 | B1 |
6565757 | Wedkamp | May 2003 | B1 |
7341695 | Garner | Mar 2008 | B1 |
7953326 | Farr et al. | May 2011 | B2 |
20010053332 | Omasa | Dec 2001 | A1 |
20020030011 | Constantine et al. | Mar 2002 | A1 |
20020100679 | Wedekamp | Aug 2002 | A1 |
20030047518 | Heidal et al. | Mar 2003 | A1 |
20040007538 | Siriphraiwan | Jan 2004 | A1 |
20060011558 | Fencl et al. | Jan 2006 | A1 |
20070115672 | Nelson et al. | May 2007 | A1 |
20100006036 | Ochoa Disselkoen | Jan 2010 | A1 |
20100176056 | Rozenberg | Jul 2010 | A1 |
20100224562 | Rolchigo et al. | Sep 2010 | A1 |
20120050520 | Thoren et al. | Mar 2012 | A1 |
Number | Date | Country |
---|---|---|
2617027 | Oct 1977 | DE |
5675290 | Jun 1981 | JP |
WO-0079246 | Dec 2000 | WO |
WO-03016222 | Feb 2003 | WO |
WO-03034817 | May 2003 | WO |
WO-2004002895 | Jan 2004 | WO |
WO-2010022057 | Feb 2010 | WO |
WO-2011049277 | Apr 2011 | WO |
Entry |
---|
International Search Report and Written Opinion for PCT/US2013/050318 mailed Nov. 6, 2013 (12 pages). |
Number | Date | Country | |
---|---|---|---|
20140078584 A1 | Mar 2014 | US |
Number | Date | Country | |
---|---|---|---|
61671426 | Jul 2012 | US |