On the Development of Focused Ultrasound Liquid Atomizers

Table 1

Summary of the available methods for atomization.

Method	Schematic and properties	Droplet size and Flow rate	Advantages	Disadvantages
SAW [38, 39]	2.3 W; 48 MHz, 36 V	5 μm; 10.2 mL/h	Small size & low power	IDT fabrication process & very high frequency & big droplets
SAW driving structure consisting of a unidirectional interdigital transducer, a horn, and a waveguide [40]	1 W; 78 MHz	1.5 μm; 2.4 mL/h	Small size & smaller droplets & low power	Very low flow rate & IDT fabrication & high frequency
Arrays of 5 μm diameter micromachined nozzles [41, 42]	36 kHz; 70, 80 V	5–10 μm,; According to [19] for typical frequencies of around 100 kHz, it is 4 μm	Small size & low frequency	Fabrication & big droplets
MEM Fourier-horn ultrasonic nozzle with central channel [43]	0.25 W; 971 kHz	4.5 μm; 21 mL/h	Small size & excellent low power	Fabrication & big droplets & average flow rate
MEM Fourier-horn ultrasonic nozzle without central channel (externally fed) [17]	80 mW; 2 MHz	2.9–4.6 μm; 25 mL/h	Small size & excellent low power	Fabrication & average droplets & average flow rate
MEM Fourier-horn ultrasonic nozzle without central channel (externally fed) [18]	0.27 W; 2 MHz	2–5 μm & Typically = 3.5 μm; Max 21 mL/h & Typically = 9 mL/h	Pocket Size & battery operated & excellent low power	Fabrication & average droplets & average or low flow rate
Current vibrating plate transducers [44–47]	2–30 W; 1.65–3 MHz	1–5 μm; 5–400 mL/h	Various droplet size and flow rate	Low-power devices with small droplets have low flow rate