Enabling practical surface acoustic wave nebulizer drug delivery via amplitude modulation
A practical, commercially viable microfluidic device relies upon the miniaturization and integration of all its components—including pumps, circuitry, and power supply—onto a chip-based platform. Surface acoustic waves (SAW) have become popular in microfluidic manipulation, in solving the problems of microfluidic manipulation, but practical applications employing SAW still require more power than available via a battery. Introducing amplitude modulation at 0.5–40 kHz in SAW nebulization, which requires the highest energy input levels of all known SAW microfluidic processes, halves the power required to 1.5 W even while including the power in the sidebands, suitable for small lithium ion batteries, and maintains the nebulization rate, size, and size distributions vital to drug inhalation therapeutics. This simple yet effective means to enable an integrated SAW microfluidics device for nebulization exploits the relatively slow hydrodynamics and is furthermore shown to deliver shear-sensitive biomolecules—plasmid DNA and antibodies as exemplars of future pulmonary gene and vaccination therapies—undamaged in the nebulized mist. Altogether, the approach demonstrates a means to offer truly micro-scale microfluidics devices in a handheld, battery powered SAW nebulization device.