Abstract
The development of a novel lead-free microelectromechanical-system (MEMS)-based atomizer using the principle of thermal bubble actuation is presented. It is a low-cost, lead-free design that is environmentally friendly and harmless to humans. It has been tested to be applicable over a wide range of fluid viscosities, ranging from 1 cP (e.g., water) to 200 cP (e.g., oil-like fluid) at room temperature, a range that is difficult to achieve using ordinary atomizers. The results demonstrate that the average power consumption of the atomizer is approximately 1 W with an atomization rate of 0.1 to 0.3 mg of deionized (DI) water per cycle. The relationships between the micro-heater track width and the track gap, the size of the micro-cavities and the nucleation energy were studied to obtain an optimal atomizer design. The particle image velocimetry (PIV) results indicate that the diameter of the ejected droplets ranges from 30 to 90 μm with a speed of 20 to 340 mm/s. In addition, different modes of spraying are reported for the first time. It is envisioned that the successful development of this MEMS-based atomizing technology will revolutionize the existing market for atomizers and could also benefit different industries, particularly in applications involving viscous fluids.
Highlights
To aerosolize viscous fluids, whereas jet atomizers are inefficient and inconvenient because compressed air is needed[18,19,20]
Heterogeneous nucleation typically occurs at a considerably less extreme superheating condition compared to homogeneous nucleation, which requires an extremely high superheating rate (i.e., Skripov’s experiment indicated that a heating rate of 107 K/s is required for a platinum wire with a diameter of 20 μm)[24,25,26,27]
As noted in the discussion section, the minimum heater temperature required for bubble nucleation is between 107 and 285 °C
Summary
To aerosolize viscous fluids, whereas jet atomizers are inefficient and inconvenient because compressed air is needed[18,19,20]. The technology is based on micro-thermal bubble actuation under a pulse heating mode, which is a simple, low cost, and–most importantly–biocompatible and nontoxic approach This thermal bubble actuation technique is widely used in inkjet printing systems, and numerous studies have been devoted to its investigation[21,22,23]. The atomizer presented in this study generates bubbles through heterogeneous nucleation, as there are numerous micro-cavities on the surface of the micro-heaters. These micro-cavities, whose diameters range from 0.2 to 5 μm, as shown, can serve as boiling sites, known as bubble nucleation sites[28,29,30,31,32]. We will discuss the design, experimental results and characteristics of a lead-free atomizer employing heterogeneous bubble nucleation
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