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Los Alamos National Security, LLC

Naveen N Sinha

Dipen N Sinha

Gregory Russ Goddard

Greg Goddard

Apparatus and methods for using acoustic radiation forces to order particles suspended in a host liquid are described. The particles may range in size from nanometers to millimeters, and may have any shape. The suspension is placed in an acoustic resonator cavity, and acoustical energy is supplied thereto using acoustic transducers. The resulting pattern may be fixed by using a solidifiable host liquid, forming thereby a solid material. Patterns may be quickly generated; typical times ranging from a few seconds to a few minutes. In a one-dimensional arrangement, parallel layers of particles are formed. With two and three dimensional transducer arrangements, more complex particle configurations are possible since different standing-wave patterns may be generated in the resonator. Fabrication of periodic structures, such as metamaterials, having periods tunable by varying the frequency of the acoustic waves, on surfaces or in bulk volume using acoustic radiation forces, provides great flexibility in the creation of new materials. Periodicities may range from millimeters to sub-micron distances, covering a large portion of the range for optical and acoustical metamaterials.

Material fabrication using acoustic radiation forces

An apparatus and method is described for measuring properties of bubbles from which certain physical characteristics of the liquid in which the bubbles are generated can be determined. The evolution of a bubble includes (1) formation and growth at a nozzle disposed within the liquid through which a gas is flowed, or formation and growth as a result of cavitation in the liquid from the application of focused acoustic energy to a location within the liquid; (2) detachment and resonance; and (3) rise towards terminal velocity. Measurements of the resonance frequency, the shape oscillation frequency and the terminal velocity of the bubble allow the determination of the density and surface tension of the liquid and the radius of the bubble. Since the properties of the liquid affect the evolution of the bubble, observation of a rising bubble can be used as a tool for characterizing the liquid; as an example, the present invention can be used to monitor changes in the liquid itself or changes in the concentration or integrity of materials dissolved in the liquid.

Characterization of liquids using gas bubbles

A method using ultrasound for detecting the presence of coatings on metal surfaces is described. The characteristics of resonant sound waves established within a metal plate are altered by the acoustic impedance of any coatings present on the surface of the metal in the vicinity of the waves. The amplitude and width of the resonant features are most directly affected and can readily be detected. For example, a reduction of approximately a factor of ten in resonance amplitude has been observed when ice is permitted to coat the surface of the plate. A resonant ultrasound condition is impressed on the plate using a transducer attached thereto on the side of the plate opposite to the coating. A receiving transducer is located next to the resonance inducing transducer. Thus, ice can be detected on the surface of an airplane wing surface using transducers located within the wing's interior. Thin deposits of materials may be detected on the interior surface of a pipe using separated transducers located on the exterior thereof.

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Los Alamos, NM, United States of America

Naveen N Sinha