  The deposition of micron particles finds importance in meteorology and
several engineering applications such as deposition of dust in gas lines,
carbon deposition in engine exhaust, designing effective air-cleaning systems
and estimating deposition of inhaled drug or atmospheric pollutants to
determine its consequences on human health. Although the existing literature on
deposition in straight tubes is quite mature, an experimental study on
deposition in micro capillaries with a wide ranges of Re that models particle
dynamics in lungs, is missing. The deposition of atmospheric pollutants and
nebulized drugs in the lung depends on various biological factors such as flow
properties, lung morphology, breathing patterns, particle properties,
deposition mechanism, etc. To complicate matters, each breath manifests flows
spanning a wide range of Reynolds numbers in various regions of the lung. In
this study, the deposition of nebulized aerosol was experimentally investigated
in phantom bronchioles of diameters relevant to the 7th to the 23rd branching
generations and over the entire range of Re manifest during one breathing
cycle. The aerosol fluid was loaded with boron doped carbon quantum dots as a
fluorophore. An aerosol was generated of this mixture fluid using an ultrasonic
nebulizer, producing droplets of 6.5$\mu$m as the mean diameter. The amount of
aerosol deposited on the bronchiole walls was measured using a
spectrofluorometer. Finally, a universal bronchiole scale deposition model is
proposed which can form the building block for lung-scale aerosol deposition
prediction.
