Ultrasonic nozzle

Last updated
Rendering of an ultrasonic nozzle Microspray Focused Ultrasonic Nozzle.JPG
Rendering of an ultrasonic nozzle

Ultrasonic nozzles are a type of spray nozzle that use high frequency vibrations produced by piezoelectric transducers acting upon the nozzle tip that create capillary waves in a liquid film. Once the amplitude of the capillary waves reaches a critical height (due to the power level supplied by the generator), they become too tall to support themselves and tiny droplets fall off the tip of each wave resulting in atomization. [1]

Contents

The primary factors influencing the initial droplet size produced are frequency of vibration, surface tension, and viscosity of the liquid. Frequencies are commonly in the range of 20–180 kHz, beyond the range of human hearing, where the highest frequencies produce the smallest drop size. [2]

History

In 1962 Dr. Robert Lang followed up on this work, essentially proving a correlation between his atomized droplet size relative to Rayleigh's liquid wavelength. [1] Ultrasonic nozzles were first commercialized by Dr. Harvey L. Berger. USA 3861852,"Fuel burner with improved ultrasonic atomizer",published Jan 21, 1975, assigned to Harvey Berger .

Applications

Subsequent uses of the technology include coating blood collection tubes, spraying flux onto printed circuit boards, coating implantable drug eluting stents and balloon/catheters, float glass manufacturing coatings, [3] anti-microbial coatings onto food, [4] precision semiconductor coatings and alternative energy coatings for solar cell and fuel cell manufacturing, among others.

PEM active layer deposition by ultrasonic spraying. Ultrasonic spraying first creates tiny droplets that deposit on the surface of the Nafion membrane, creating a uniform layer of platinum-carbon catalyst Patrick Teppor and PEM active layer deposition by ultrasonic spraying.jpg
PEM active layer deposition by ultrasonic spraying. Ultrasonic spraying first creates tiny droplets that deposit on the surface of the Nafion membrane, creating a uniform layer of platinum-carbon catalyst

Drug eluting stents and drug-coated balloons

Pharmaceuticals such as Sirolimus (also called Rapamycin) and Paclitaxel are coated on the surface of drug eluting stents (DES) and drug-coated balloons (DCB). These devices benefit greatly from ultrasonic spray nozzles for their ability to apply coatings with little to no loss. Medical devices such as DES and DCB require very narrow spray patterns, a low-velocity atomized spray and low-pressure air because of their small size. [5]

Fuel cells

Research has shown that ultrasonic nozzles can be effectively used to manufacture proton exchange membrane fuel cells. The inks typically used are a platinum-carbon suspension, where the platinum acts as a catalyst inside the cell. Traditional methods to apply the catalyst to the proton exchange membrane typically involve screen printing or doctor-blades. However, these methods can result in undesirable cell performance due to the tendency of the catalyst to form agglomerations resulting in non-uniform gas flow in the cell and prohibiting the catalyst from being fully exposed, running the risk that the solvent or carrier liquid may be absorbed into the membrane, both of which impeded proton exchange efficiency. [6] When ultrasonic nozzles are used, the spray can be made to be as dry as necessary by the nature of the small and uniform droplet size, by varying the distance the droplets travel and by applying low heat to the substrate such that the droplets dry in the air before reaching the substrate. Process engineers have finer control over these types of variables as opposed to other technologies. Additionally, because the ultrasonic nozzle imparts energy to the suspension just prior to and during atomization, possible agglomerates in the suspension are broken up resulting in homogenous distribution of the catalyst, resulting in higher efficiency of the catalyst and in turn, the fuel cell. [7] [8]

Transparent conductive films

Ultrasonic spray nozzle technology has been used to create films of indium tin oxide (ITO) in the formation of transparent conductive films (TCF). [9] ITO has excellent transparency and low sheet resistance, however it is a scarce material and prone to cracking, which does not make it a good candidate for the new flexible TCFs. Graphene on the other hand can be made into a flexible film, extremely conductive and has high transparency. Ag nanowires (AgNWs) when combined with Graphene have been reported to be a promising superior TCF alternative to ITO. [10] Prior studies focus on spin and bar coating methods which are not suitable for large area TCFs. A multi-step process utilizing ultrasonic spray of graphene oxide and conventional spray of AgNWs followed by a hydrazine vapor reduction, followed by the application of polymethylmethacrylate (PMMA) topcoat resulted in a peelable TCF that can be scaled to a large size. [11]

Carbon nanotubes

CNT thin films are used as alternative materials to create transparent conducting films (TCO layers) [12] for touch panel displays or other glass substrates, as well as organic solar cell active layers. [13]

Photoresist spray onto MEMs wafers

Microelectromechanical systems (MEMs) [14] are small microfabricated devices that combine electrical and mechanical components. Devices vary in size from below one micron to millimeters in size, functioning individually or in arrays to sense, control, and activate mechanical processes on the micro scale. Examples include pressure sensors, accelerometers, and microengines. Fabrication of MEMs involves depositing a uniform layer of photoresist [15] onto the Si wafer. Photoresist has traditionally been applied to wafers in IC manufacturing using a spin coating technique. [16] In complex MEMs devices that have etched areas with high aspect ratios, it can be difficult to achieve uniform coverage along the top, side walls, and bottoms of deep grooves and trenches using spin coating techniques due to the high rate of spin needed to remove excess liquid. Ultrasonic spray techniques are used to spray uniform coatings of photoresist onto high aspect ratio MEMs devices and can minimize usage and overspray of photoresist. [17]

Printed circuit boards

The non-clogging nature of ultrasonic nozzles, the small and uniform droplet size created by them, and the fact that the spray plume can be shaped by tightly controlled air shaping devices makeS the application quite successful in wave soldering processes. The viscosity of nearly all fluxes on the market fit well within the capabilities of the technology. In soldering, "no-clean" flux is highly preferred. But if excessive quantities are applied the process will result in corrosive residues on the bottom of the circuit assembly. [18]

Solar cells

Photovoltaic and dye-sensitized solar technology both need the application of liquids and coatings during the manufacturing process. With most of these substances being very expensive, any losses due to over-spray or quality control are minimized with the use of ultrasonic nozzles. In efforts to reduce the manufacturing costs of solar cell, traditionally done using the batch-based phosphoryl chloride or POCl3 method, it has been shown that using ultrasonic nozzles to lay a thin aqueous-based film onto silicon wafers can effectively be used as a diffusion process to create N-type layers with uniform surface resistance. [19]

Ultrasonic spray pyrolysis

Ultrasonic spray pyrolysis is a chemical vapor deposition (CVD) method utilized in the formation of a variety of materials in thin film or nanoparticle form. Precursor materials are often fabricated through sol-gel methods and examples include the formation of aqueous silver nitrate, [20] synthesis of zirconia particles, [21] and fabrication of solid oxide fuel cell SOFC cathodes. [22]

High Temperature Ultrasonic Nozzle High Temperature Nozzle.png
High Temperature Ultrasonic Nozzle

An atomized spray produced from an ultrasonic nozzle is subjected to a heated substrate typically ranging from 300–400 degrees C. [23] Due to the high temperatures of the spray chamber, extensions to the ultrasonic nozzle (as pictured and labeled – High Temperature Ultrasonic Nozzle)[ citation needed ] such as a removable tip (tip is hidden under the vortex air shroud labeled #2)[ citation needed ] have been designed to be subjected to high temperatures while protecting the body (labeled #1) [ citation needed ] of the ultrasonic nozzle that contains temperature sensitive piezoelectric elements, typically outside of the spray chamber or by other means of isolation. [24]

Related Research Articles

<span class="mw-page-title-main">Chemical vapor deposition</span> Method used to apply surface coatings

Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films.

<span class="mw-page-title-main">Spray drying</span> Method of converting liquid or slurry to powder

Spray drying is a method of forming a dry powder from a liquid or slurry by rapidly drying with a hot gas. This is the preferred method of drying of many thermally-sensitive materials such as foods and pharmaceuticals, or materials which may require extremely consistent, fine particle size. Air is the heated drying medium; however, if the liquid is a flammable solvent such as ethanol or the product is oxygen-sensitive then nitrogen is used.

<span class="mw-page-title-main">Roll-to-roll processing</span>

In the field of electronic devices, roll-to-roll processing, also known as web processing, reel-to-reel processing or R2R, is the process of creating electronic devices on a roll of flexible plastic, metal foil, or flexible glass. In other fields predating this use, it can refer to any process of applying coating, printing, or performing other processes starting with a roll of a flexible material and re-reeling after the process to create an output roll. These processes, and others such as sheeting, can be grouped together under the general term converting. When the rolls of material have been coated, laminated or printed they can be subsequently slit to their finished size on a slitter rewinder.

<span class="mw-page-title-main">Spray painting</span> Painting technique in which a device sprays coating material through the air onto a surface

Spray painting is a painting technique in which a device sprays coating material through the air onto a surface. The most common types employ compressed gas—usually air—to atomize and direct the paint particles.

<span class="mw-page-title-main">Nebulizer</span> Drug delivery device

In medicine, a nebulizer or nebuliser is a drug delivery device used to administer medication in the form of a mist inhaled into the lungs. Nebulizers are commonly used for the treatment of asthma, cystic fibrosis, COPD and other respiratory diseases or disorders. They use oxygen, compressed air or ultrasonic power to break up solutions and suspensions into small aerosol droplets that are inhaled from the mouthpiece of the device. An aerosol is a mixture of gas and solid or liquid particles.

<span class="mw-page-title-main">Proton-exchange membrane fuel cell</span> Power generation technology

Proton-exchange membrane fuel cells (PEMFC), also known as polymer electrolyte membrane (PEM) fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges and a special proton-conducting polymer electrolyte membrane. PEMFCs generate electricity and operate on the opposite principle to PEM electrolysis, which consumes electricity. They are a leading candidate to replace the aging alkaline fuel-cell technology, which was used in the Space Shuttle.

<span class="mw-page-title-main">Thermal spraying</span> Coating process for applying heated materials to a surface

Thermal spraying techniques are coating processes in which melted materials are sprayed onto a surface. The "feedstock" is heated by electrical or chemical means.

<span class="mw-page-title-main">Printed electronics</span> Electronic devices created by various printing methods

Printed electronics is a set of printing methods used to create electrical devices on various substrates. Printing typically uses common printing equipment suitable for defining patterns on material, such as screen printing, flexography, gravure, offset lithography, and inkjet. By electronic-industry standards, these are low-cost processes. Electrically functional electronic or optical inks are deposited on the substrate, creating active or passive devices, such as thin film transistors; capacitors; coils; resistors. Some researchers expect printed electronics to facilitate widespread, very low-cost, low-performance electronics for applications such as flexible displays, smart labels, decorative and animated posters, and active clothing that do not require high performance.

<span class="mw-page-title-main">Spray nozzle</span> Device that facilitates dispersion of liquid into a spray

A spray nozzle or atomizer is a device that facilitates the dispersion of a liquid by the formation of a spray. The production of a spray requires the fragmentation of liquid structures, such as liquid sheets or ligaments, into droplets, often by using kinetic energy to overcome the cost of creating additional surface area. A wide variety of spray nozzles exist, that make use of one or multiple liquid breakup mechanisms, which can be divided into three categories: liquid sheet breakup, jets and capillary waves. Spray nozzles are of great importance for many applications, where the spray nozzle is designed to have the right spray characteristics.

Platinum black is a fine powder of platinum with good catalytic properties. The name of platinum black is due to its black color. It is used in many ways; as a thin film electrode, a fuel cell membrane catalyst, or as a catalytic ignition of flammable gases for "self-lighting' gas lamps, ovens, and stove burners.

<span class="mw-page-title-main">Transparent conducting film</span> Optically transparent and electrically conductive material

Transparent conducting films (TCFs) are thin films of optically transparent and electrically conductive material. They are an important component in a number of electronic devices including liquid-crystal displays, OLEDs, touchscreens and photovoltaics. While indium tin oxide (ITO) is the most widely used, alternatives include wider-spectrum transparent conductive oxides (TCOs), conductive polymers, metal grids and random metallic networks, carbon nanotubes (CNT), graphene, nanowire meshes and ultra thin metal films.

Ultra-high-purity steam, also called the clean steam, UHP steam or high purity water vapor, is used in a variety of industrial manufacturing processes that require oxidation or annealing. These processes include the growth of oxide layers on silicon wafers for the semiconductor industry, originally described by the Deal-Grove model, and for the formation of passivation layers used to improve the light capture ability of crystalline photovoltaic cells. Several methods and technologies can be employed to generate ultra high purity steam, including pyrolysis, bubbling, direct liquid injection, and purified steam generation. The level of purity, or the relative lack of contamination, affects the quality of the oxide layer or annealed surface. The method of delivery affects growth rate, uniformity, and electrical performance. Oxidation and annealing are common steps in the manufacture of such devices as microelectronics and solar cells.

<span class="mw-page-title-main">Spray (liquid drop)</span> Dynamic collection of drops dispersed in a gas

A spray is a dynamic collection of drops dispersed in a gas. The process of forming a spray is known as atomization. A spray nozzle is the device used to generate a spray. The two main uses of sprays are to distribute material over a cross-section and to generate liquid surface area. There are thousands of applications in which sprays allow material to be used most efficiently. The spray characteristics required must be understood in order to select the most appropriate technology, optimal device and size.

<span class="mw-page-title-main">Chemistry of photolithography</span> Overview article

Photolithography is a process in removing select portions of thin films used in microfabrication. Microfabrication is the production of parts on the micro- and nano- scale, typically on the surface of silicon wafers, for the production of integrated circuits, microelectromechanical systems (MEMS), solar cells, and other devices. Photolithography makes this process possible through the combined use of hexamethyldisilazane (HMDS), photoresist, spin coating, photomask, an exposure system and other various chemicals. By carefully manipulating these factors it is possible to create nearly any geometry microstructure on the surface of a silicon wafer. The chemical interaction between all the different components and the surface of the silicon wafer makes photolithography an interesting chemistry problem. Current engineering has been able to create features on the surface of silicon wafers between 1 and 100 μm.

Liquid–feed flame spray pyrolysis (LF-FSP) is one of the most recent iterations in flame spray pyrolysis (FSP) powder production technology. FSP produces metal oxide powders from highly volatile gaseous metal chlorides that are decomposed/oxidized in hydrogen-oxygen flames to form nano-oxide powders. However, products made from FSP's vapor-phase process are limited to Al-, Ti-, Zr-, and Si-based oxides from their metal chlorides. Thus, interest in producing more complex materials required a new methodology, LF-FSP.

<span class="mw-page-title-main">Metal powder</span> Metal broken down to powder form

Metal powder is a metal that has been broken down into a powder form. Metals that can be found in powder form include aluminium powder, nickel powder, iron powder and many more. There are four different ways metals can be broken down into this powder form:

Patternation is the specialized technical art of performing quantitative measurements of specific properties of particles within a spray and visualizing the patterns of this specific property within the spray. In order to understand patternation, we need to consider the role sprays play in our daily lives.

<span class="mw-page-title-main">Harvey L. Berger</span>

Harvey Berger was a scientist and inventor. He invented the modern commercial ultrasonic nozzle, which in its application has brought many benefits to the fields of research, combustion and manufacturing. Berger founded Sono-Tek Corporation based on this technology and while working at the company he made contributions to the fields of combustion, semiconductor manufacturing, electronic printed circuit board manufacturing, drug eluting stents and spray drying. Berger died in August 2007 after a struggle with liver cancer. He was survived by his wife Donna and by his three children, Michael, Robyn and Barbara.

Graphene spray guns are a kinetic spray system that deposits, through supersonic acceleration, a one atom thick sheet of pure carbon named graphene by means of a de Laval nozzle, which is a pinched tube with an hourglass type shape. The system deposits graphene flakes and a hexagonal graphene lattice is created upon impact of the desired surface. The graphene spray gun would be utilized onto large-scale applications such as circuits, radio transmitters, and optical electronics due to its transparency and its high electrical conductivity. The supersonic spray system was first developed in May 2014 by University of Illinois professor Alexander Yarin, and Korea University professor Sam Yoon. Yarin went to Yoon when he learned about his work regarding kinetic spray deposition systems. Yarin believed that graphene could be applied to the system in order to create a layer of the material. After conducting experiments with the newly created system, they concluded that the graphene spray system was a success. The spray gun is still in its early stages of development, but is considered by many scientists and researchers to be the solution of various predicaments that occur when applying graphene onto large-scale products. The most common problem that would transpire within the other methods is that the layer would be uneven and coated by aggregations. The energy delivered by the supersonic spraying stretches the graphene evenly upon impact, and is the main reason for the spray system’s lack of defects that are common within other graphene deposition methods.

Rotary atomizers use a high speed rotating disk, cup or wheel to discharge liquid at high speed to the perimeter, forming a hollow cone spray. The rotational speed controls the drop size. Spray drying and spray painting are the most important and common uses of this technology.

References

  1. 1 2 Lang, Robert (1962). "Ultrasonic Atomization of Liquids". The Journal of the Acoustical Society of America. 34 (1): 6. Bibcode:1962ASAJ...34....6L. doi:10.1121/1.1909020.
  2. ↑ Berger, Harvey (1998). Ultrasonic Liquid Atomization Theory and Application. Hyde Park, NY: Partridge Hill Publishers. p. 44. ISBN   978-0-9637801-5-7.
  3. ↑ Davis, Nancy (Feb 2005). "Ultrasonic Spray for Glass Manufacturing" (PDF). Glass Magazine.
  4. ↑ DiNapoli, Jessica (2013-10-10). "Sono-Tek targets food safety". Times Herald-Record.
  5. ↑ Berger, Harvey. "Director of Technology". European Medical Device Technology. Retrieved 7 February 2014.
  6. ↑ Wheeler, D; Sverdrup, G. (March 2008). "Status of Manufacturing: Polymer Electrolyte Membrane (PEM) Fuel Cells" (PDF). Technical Report. NREL/TP-560-41655: 6. doi:10.2172/924988.{{cite journal}}: |volume= has extra text (help)
  7. ↑ Engle, Robb (2011-08-08). MAXIMIZING THE USE OF PLATINUM CATALYST BY ULTRASONIC SPRAY APPLICATION (PDF). Proceedings of Asme 2011 5Th International Conference on Energy Sustainability & 9Th Fuel Cell Science, Engineering and Technology Conference. Vol. ESFUELCELL2011-54369. pp. 637–644. doi:10.1115/FuelCell2011-54369. ISBN   978-0-7918-5469-3.
  8. ↑ Millington, Ben; Vincent Whipple; Bruno G Pollet (2011-10-15). "A novel method for preparing proton exchange membrane fuel cell electrodes by the ultrasonic-spray technique". Journal of Power Sources. 196 (20): 8500–8508. Bibcode:2011JPS...196.8500M. doi:10.1016/j.jpowsour.2011.06.024.
  9. ↑ Z.B. Zhoua, R.Q. Cuia, Q.J. Panga, Y.D. Wanga, F.Y. Menga, T.T. Suna, Z.M. Dingb, X.B. Yub, 2001, "," Preparation of indium tin oxide films and doped tin oxide films by an ultrasonic spray CVD process, Volume 172, Issues 3-4
  10. ↑ Young Soo Yun, Do Hyeong Kim, Bona Kim, Hyun Ho Park, Hyoung-Joon Jin, 2012, "," Transparent conducting films based on graphene oxide/silver nanowire hybrids with high flexibility, Synthetic Metals, Volume 162, Issues 15–16, Pages 1364–1368
  11. ↑ Young-Hui Koa, Ju-Won Leeb, Won-Kook Choic, Sung-Ryong Kim, 2014, "," Ultrasonic Sprayed Graphene Oxide and Air Sprayed Ag Nanowire for the Preparation of Flexible Transparent Conductive Films, The Chemical Society of Japan
  12. ↑ Majumder, Mainak; et al. (2010). "Insights into the physics of spray coating SWNT films". Chemical Engineering Science. 65 (6): 2000–2008. Bibcode:2010ChEnS..65.2000M. doi:10.1016/j.ces.2009.11.042.
  13. ↑ Steirer, K. Xerxes; et al. (2009). "Ultrasonic spray deposition for production of organic solar cells". Solar Energy Materials & Solar Cells. 93 (4): 447–453. doi:10.1016/j.solmat.2008.10.026.
  14. ↑ "Microelecromechanical Systems (MEMS)".
  15. ↑ "Pattern Transfer".
  16. ↑ "Semiconductor Lithography (Photolithography) - The Basic Process".
  17. ↑ "Process for Coating a Photoresist Composition onto a Substrate".
  18. ↑ Rathinavelu, Umadevi. "Effect of No-Clean Flux Residues on the Performance of Acrylic Conformal Coating in Aggressive Environments" (PDF). IEEE.
  19. ↑ Voyer, Catherine (June 7, 2004). "Evaluation of Dopant Sources and Deposition Methods Suitable for In-Line Diffusion in the PV Industry". 19th European Photovoltaic Energy Conference: 848.
  20. ↑ Kalyana C. Pingali, David A. Rockstraw, and Shuguang Deng, 2005, "Silver Nanoparticles from Ultrasonic Spray Pyrolysis of Aqueous Silver Nitrate," Aerosol Science and Technology, 39:1010-1014
  21. ↑ Y. L. Song, S. C. Tsai, C. Y. Chen, T. K. Tseng, C. S. Tsai, J. W. Chen, and Y. D. Yao, 2004, "Ultrasonic Spray Pyrolysis for Synthesis of Spherical Zirconia Particles" Journal of the American Ceramic Society, Vol.87, No. 10
  22. ↑ Hoda Amani Hamedani, 2008, Investigation of Deposition Parameters in Ultrasonic Spray Pyrolysis for Fabrication of Solid Oxide Fuel Cell Cathode, Georgia Institute of Technology
  23. ↑ Nakaruk, A; D.S. Perera (Nov 6, 2010). "Influence of Deposition Temperature on Titania Films Deposited by Ultrasonic Spray Pyrolysis". The AZo Journal of Materials Online.
  24. ↑ Carstens, James (1993). Electrical sensors and transducers. Regents/Prentice Hall. pp. 185–199. ISBN   978-0132496322.

Berger, Harvey L. Ultrasonic Liquid Atomization: Theory and Application. 2nd ed. Hyde Park: Partrige Hill, 2006. 1-177.

Lefebvre, Arthur, Atomization and Sprays, Hemisphere, 1989, ISBN   0-89116-603-3

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.