Acoustic Ejector with Novel Lens Employing Air-Reflectors

This paper describes a novel droplet ejector with an acoustic lens employing air-reflectors. The lens focuses the acoustic beams at the liquid surface, and facilitates uniform and consistent droplet ejections. This acoustic ejector requires no nozzle, nor heat for actuation, but uses a novel lens. When excited with RF pulses (7μs pulsewidth) of 18 MHz (corresponding to the fundamental thickness-mode resonant frequency), the ejector ejects uniform droplets of 70 μm in diameter at a rate up to 10 kHz. The ejector is integrated with reservoirs and channels on a single chip, and is shown to produce continuous and stable ejections without any liquid refilling or frequency tuning.