Generation and Evaporation of Microsprays

This chapter aims to comprehensively review the techniques and features of micro-sprays for various applications via micro-droplet generators over decades, especially focusing on the past and present microfluidics. It is organized briefly as below. The background of current research and development about the micro-spray techniques is first introduced, followed by the generation and evaporation of spray detailed with the concentrated respects of critical requirements for materials and facilities. Then, we address the critical design issues of micro-sprayers such as the actuators and nozzles required to be satisfactory for generating a number of droplets. Subsequently, we further describe characterization of droplets in form of spray concerning droplet size, speed, rates, and patterns in microfluidics. Moreover, the chapter presents the proof-of-concept and commercial applications of the micro-spraying processes, highlighting their current technical progresses and future challenges, which shall be intimately related to the droplet generation and evaporation including droplet evaporative cooling, direct printing, screen printing, nano-material coating, liquid nebulization, and miscellaneous employment. Finally, we draw a conclusion in the end of the chapter

Effects of Driving Frequency and Voltage on the Performances of Vibrating Mesh Nebulizers

The functional components of vibrating mesh nebulizers are a piezoelectric ceramic with a mesh mounted on one side, a reservoir, and a driving circuit. The piezoelectric material vibrates at a specific intrinsic frequency, and when the mechanical resonance frequency of the piezoelectric ceramic and the frequency of the applied electrical signal match, the vibration amplitude of the ceramic is greatest. In the present study, nebulizing performances were tested with respect to driving voltage amplitude after automatic resonance frequency tuning (ARFT) and/or impedance matching (IM) for salbutamol and glycerol solutions. A 1% mismatch of resonance frequency reduced the output rate by 11.0~30.1% and increased particle size by 1.6~7.7% and power consumption increased by 6.6~13.6%. Driving at 30 Vpp after ARFT and IM increased output rate by 45% and decreased power consumption by 31% compared with operation at nominal resonance frequency without IM at 50 Vpp. Nebulization of viscous solutions was also enhanced by applying ARFT with IM. The study shows the application of ARFT with IM improves vibrating mesh nebulizer performance and reduces power consumption.ope