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The possibility of protein release from polymeric microcapsules by means of low-power (up to a maximum of 3.2 W) high-frequency (850 kHz) ultrasound was studied. The release efficiency using these ultrasonic parameters that are close to those currently used in medical diagnostic and ultrasound treatment was compared to that achieved with a conventional 20 kHz 70 W ultrasonic probe. Microcapsules were made by polyelectrolyte multilayer assembly on 3-5 mm calcium carbonate particles with co-precipitated fluorescently labelled protein. Ultrasound induced protein release was monitored by supernatant fluorescence increase after sonication. The release efficiency is improved by the presence of gold nanoparticles in the microcapsule shell. The amount of gold nanoparticles in the shell was found to play an important role in release efficiency. The irradiation was carried out at several intensities and exposure times and evidence of microcapsule rupture after treatment was obtained by confocal and scanning electron microscopy.

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This paper describes the ultrasound assisted dispersal of a low wt. / vol. % copper nanopowder mixture and determines the optimum conditions for deagglomeration. A commercially available powder was added to propan-2-ol and dispersed using a magnetic stirrer, a high frequency 850 kHz ultrasonic cell, a standard 40 kHz bath and a 20 kHz ultrasonic probe. The particle size of the powder was characterized using dynamic light scattering (DLS). Zaverage diameters (mean cluster size based on the intensity of scattered light) and intensity, volume and number size distributions were monitored as a function of time and energy input. Low frequency ultrasound was found to be more effective than high frequency ultrasound at de-agglomerating the powder and dispersion with a 20 kHz ultrasonic probe was found to be very effective at breaking apart large agglomerates containing weakly bound clusters of nanoparticles. In general, the breakage of nanoclusters was found to be a factor of ultrasonic intensity, the higher the intensity the greater the deagglomeration and typically micron sized clusters were reduced to sub 100nm particles in less than 30 min using optimum conditions. However, there came a point at which the forces generated by ultrasonic cavitation were either insufficient to overcome the cohesive bonds between smaller aggregates or at very high intensities decoupling between the tip and solution occurred. Absorption spectroscopy indicated a copper core structure with a thin oxide shell and the catalytic performance of this dispersion was demonstrated by drop coating onto substrates and subsequent electroless copper metallization. This relatively inexpensive catalytic suspension has the potential to replace precious metal based colloids used in electronics manufacturing.