Faraday Waves-and Multiple-Fourier Horns-Based Ultrasonic Nozzles and Nebulizers

Inhalation is an increasingly important route for non-invasive drug delivery for both systemic and local applications. Control of particle droplet size and throughput plays a critical role in the efficient and effective delivery of often expensive medications to the lung. Drugs designed to treat pulmonary diseases or for systemic absorption through the alveolar capillary bed require optimum particle sizes (2 to 6 µm) for effective delivery. Current advanced commercial devices such as Omron and ParieFlow produce droplets or aerosols by a vibrating mesh. All these devices suffer from broad particle size (poly-disperse) distributions and lack of size control capability, and also are plagued by clogging of the mesh orifices used.The new drug delivery device presented in this dissertation has demonstrated capability for control of particle size within the optimum size range at low drive power and desirable throughput and freedom from clogging. The new device employs a novel silicon-based ultrasonic nozzle with multiple Fourier horns in resonance designed to operate based on the phenomena of Faraday waves at the frequency range of 1 to 2.5 MHz. The superior performance and batch fabrication economy of the centimeter-size nozzles have demonstrated the potential towards commercialization of the new delivery device.The nozzle consists of a drive section and a resonator section. The resonator section is made of multiple Fourier horns in cascade. The nozzle is designed to vibrate at the resonance frequency of the multiple Fourier horns. A lead zirconate titanate (PZT) piezoelectric transducer is bonded on the drive section to excite mechanical vibrations (displacement) along the nozzle axis. The PZT transducers are fed by a driving circuit. The resultant vibration amplitude on the nozzle end face (tip of the distal horn) is greatly magnified. As the liquid fed from a plastic tubing to the nozzle’s tip, a liquid layer is maintained on the surface of the nozzle tip to form standing capillary waves and production of monodisperse droplets when the tip vibration amplitude exceeds a threshold value. The major objective of this dissertation research is to devise and develop methods to accomplish a high level of performance and robustness for a standalone nebulization module. Significant advances have been made towards the objective