microgouttes

Microgouttes, or microdroplets, are tiny liquid particles dispersed in another medium, typically air. They range in diameter from a few micrometers up to several tens or hundreds of micrometers, with the lower end in the fine aerosol range and the upper end approaching droplets seen in spray systems. Their small size gives them a large surface-area-to-volume ratio and a propensity to evaporate rapidly, depending on ambient conditions and liquid properties such as volatility and surface tension.

Microgouttes are produced by atomization and spraying, as well as by condensation from vapor. Common methods include pneumatic and hydraulic atomizers, ultrasonic nebulizers, inkjet printers, and spray nozzles. The formation process depends on liquid viscosity, surface tension, nozzle geometry, and driving pressure or energy input. Evaporation can substantially reduce size after formation, sometimes leading to droplet shrinkage or complete transition to vapor before deposition.

Characterization typically involves measuring size distribution and concentration. Techniques include optical microscopy for direct imaging of larger droplets, laser diffraction or dynamic light scattering for bulk distributions, and phase Doppler anemometry or interferometric methods for noninvasive, in-flight measurements.

Applications span agriculture (pesticide and fertilizer sprays), medicine (nebulized drugs and inhalation therapies), printing and coatings (inkjet and spray-coating processes), cooling and combustion (fuel sprays and spray cooling), and microfluidics research where droplets serve as discrete reaction vessels.

Health and environmental considerations focus on inhalation exposure, deposition in the respiratory tract, and potential fogging or drift from spray operations. Control measures include optimized nozzle design, appropriate droplet size targeting, and ventilation.