Ultrasonics in Nano Coating and Nanosuspensions

Nanomaterials, such as carbon nanotubes, metal oxides and nanoclays are typically manufactured as a dry material, but when made wet as a sprayable coating will agglomerate or clump due to the cohesive nature of these materials.  Ultrasonic spray technology is ideal for breaking up agglomerates in solution.

Ultrasonic spray systems are used for creating both nano coatings onto three dimensional devices and two dimensional linear substrates as well as spraying nanosuspensions in dispersions.

Nano Coating:

Ultrasonic spray technology can be used to spray uniform nano thin coatings due to its low flow rate capabilities and high uniformity in droplet sizes.  Common application for ultrasonic spray technology is in the application:

• anti-reflection (AR) coatings on solar cells

Nanosuspensions:

The same vibration that creates an ultrasonic spray has the attribute of also inhibiting clumping or agglomeration of nano materials.  This phenomena is most prevalent in carbon nanotubes, which have a tendency to agglomerate with conventional air spray atomization, which does not benefit from the vibratory effect of ultrasonics.  Ultrasonic spray nozzles cause a liquid to vibrate through cavitation at the tip of the ultrasonic nozzle.  This vibration is what creates atomization.  On our home page there is a video showing the principals at work.   This same vibration aids in nanoparticle dispersion.  Some common nanosuspensions that are successfully applied with ultrasonic spray technology:

• Carbon nanotubes
• Nanowires and Graphene
• Metal oxides such as magnesium oxide, indium-tin oxide, cerium oxide, iron oxide, zine oxide, ceria oxide, zirconium oxide and titanium
• Transparent Conductive Oxides (TCO) in touchscreen applications.
• Pharmaceuticals

Spray Drying:

Ultrasonic nozzles are also used in spray drying applications in the production of nanoparticles both in aqueous and organic applications.  Ultrasonic spray nozzles can produce typically smaller particles sizes than conventional spray nozzles, thus ultrasonic generated droplets can more efficiently be dried in flight.  Additionally the low velocity of the spray generated increases nanoparticle yields, keeping material aloft longer and less coating of the chamber walls of a spray dryer when compared to conventional methods.  Lastly, the introduction of two separate liquid paths to the same ultrasonic nozzle can be used to create microencapsulates.

Nano Antimicrobial Coatings and Nanoclays:

Nano antimicrobials are common in the food industry as a top coat of decorative coatings and glazes as well as applying flavoring agents and spices.  Nanoclay coatings utilizing ultrasonic nozzles are applied as barrier protection on polyolefin films in the packaging industry.  These films are being applied in the food industry to extend shelf life.