Compact SAW aerosol generator.

In this work, we discuss and demonstrate the principle features of surface acoustic wave (SAW) aerosol generation, based on the properties of the fluid supply, the acoustic wave field and the acoustowetting phenomena. Furthermore, we demonstrate a compact SAW-based aerosol generator amenable to mass production fabricated using simple techniques including photolithography, computerized numerical control (CNC) milling and printed circuit board (PCB) manufacturing. Using this device, we present comprehensive experimental results exploring the complexity of the acoustic atomization process and the influence of fluid supply position and geometry, SAW power and fluid flow rate on the device functionality. These factors in turn influence the droplet size distribution, measured here, that is important for applications including liquid chromatography, pulmonary therapies, thin film deposition and olfactory displays.

SAW-based fluid atomization using mass-producible chip devices.

Surface acoustic wave (SAW)-based fluid atomizers are ideally suited to generate micrometer-sized droplets without any moving parts or nozzles. Versatile application fields can be found for instance in biomedical, aerosol or thin film technology, including medical inhalators or particle deposition for advanced surface treatment. Such atomizers also show great potential for on-chip integration and can lead to economic production of hand-held and even disposable devices, with either a single functionality or integrated in more complex superior systems. However, this potential was limited in the past by fluid supply mechanisms inadequate for mass production, accuracy and reliability. In this work, we briefly discuss existing fluid supply methods and demonstrate a straightforward new approach suited for reliable and cost-effective mass-scale manufacturing of SAW atomizer chips. Our approach is based on a fluid supply at the boundary of the acoustic beam via SU-8 microchannels produced by a novel one-layer/double-exposure photolithography method. Using this technique, we demonstrate precise and stable fluid atomization with almost ideal aerosol plume geometry from a dynamically stabilized thin fluid film. Additionally, we demonstrate the possibility of in situ altering the droplet size distribution by controlling the amount of fluid available in the active region of the chip.

Preparation of CNT-copper matrix composite films.

Copper matrix composite thin films reinforced with multiwall carbon nanotubes (CNT-Cu-MC) have been processed by electroplating on conducting or insulating underlayers on oxidized (100)Si substrates using iron catalyst particles. The nanotubes were grown by thermal or plasma enhanced catalytic CVD process. Enhanced interfacial strength to copper was achieved after covering the CNTs by plasma enhanced atomic layer deposition (PEALD) of a thin Ta-N or Ta-N/Zr-O interlayer. For copper plating a conventional copper electrolyte with additives (Ethone) was applied. The density of CNTs and their growth determine primarily the quality of the composite films. A sufficient dispersion of CNTs in the copper matrix and homogeneous copper plating were obtained for low density of CNTs. The CNT reinforcement changes the microstructure and electrical properties of electroplated copper films. The resistivity of the Cu films increases by multiwall CNT reinforcement as a result of changed microstructure.