Aerosol Capture for Coupling to Microfluidics: A Miniaturized Low-Cost Device for Size-Resolved Particle Collection

Inhaled
aerosols impact human health by depositing harmful species
in the lungs (e.g., metals and organic pollutants) and act as a key
pathway for airborne disease transmission. Aerosol inhalation is highly
size-dependent, with smaller particles (particulate matter <2.5
μm, PM2.5) depositing deeper in the lungs (e.g.,
alveoli) leading to strong correlations between PM2.5 and
mortality, along with other respiratory and cardiovascular diseases.
A longstanding challenge for detailed aerosol chemical analysis is
that most PM2.5 health studies collect offline samples,
which are subsequently analyzed offsite, requiring high-cost collectors
and significant downstream effort and cost. Herein, we present a low-cost,
miniature 3D-printed impactor coupled to a microfluidic channel to
allow for downstream analysis of PM in liquid. After size-segregated
collection of airborne particles within the device, water is flowed
through a microfluidic channel that resuspends insoluble particles
or dissolves soluble particles. Size-dependent collection efficiencies
(50% cutoff diameters, d50's) for
the
supermicron (PM>1) impactor were 0.8 and 1.0 μm
using
monodisperse (polystyrene latex spheres) and polydisperse (red-fluorescent
spheres) standards, respectively. Coarse (PM>2.5) impactor d50's were 2.4 and 2.6 μm, respectively.
Optical photothermal infrared (O-PTIR) and Raman microspectroscopy
confirmed collected particle composition. The sizes of re-entrained
PSLs (1, 1.25, and 1.5 μm) were measured to have diameters of
1.0, 1.2, and 1.5 μm, respectively, with a Coulter Counter,
indicating the successful downstream analysis of collected particles
without modification during impaction and resuspension. Soluble particles
(ammonium sulfate) were dissolved by the flowing water and measured
with ion chromatography. This study shows that 3D-printed impactors
are capable of collecting particles with a well-defined size cut,
as well as nondestructively resuspending and chemically analyzing
the particles. These 3D-printed devices are a miniaturized, low-cost
(<$2) option that sets the stage for semicontinuous microfluidic
analysis of size-selected aerosols to evaluate health impacts ranging
from toxin exposure to disease transmission.