Fig. 1. Digital holographic microscopy test platform based on inertial impact sampling. (a) Schematic of the platform with inertial impactor; (b) illustration of the prototype design; (c) experimental prototype

Fig. 2. Schematic of in-line holography

Fig. 3. Schematic diagrams of inertial impact sampling and inertial separation. (a) Illustration of the particle release at t=0 s; (b) illustration of particle impaction on the deposition section over a short time period t=0.01 s; (c) the correlation between particle position, mass density and particle size on the sample plate

Fig. 4. Distribution maps of four types of particles with a diameter of 5 μm. (a) The deposition distribution of Silica, PMMA, PS, and PMSQ particles in the sampler; (b) histogram of the positions of Silica, PMMA, PS, and PMSQ particles in the sampler

Fig. 5. Illustration of particle refractive index measurement. (a)‒(c) Normalized holograms of 5 μm diameter Silica particles, numerical fitting of Lorenz-Mie theory and azimuth-mean radial profile, the blue scatter points in the radial profile are the experimental data, the blue solid line represents the angular average when fitting to Lorenz-Mie theory, the dashed red-green curves indicate the standard deviations of the average; (d)‒(f) (g)‒(i) (j)‒(l) fitting process and data of PMMA, PS, and PMSQ particles with a diameter of 5 μm; (m) the retrieved particle diameter and refractive index, the horizontal and vertical bars mark the deviation from the reference values provided by the manufacturer; (n) the histogram of particles with different refractive indices when the diameters are fixed to be 5 μm, all scales are 20 μm

Fig. 6. Illustration of particle refractive index measurement. (a)‒(c) Normalized holograms of 30 μm diameter Silica particles, numerical fitting of Lorenz-Mie theory and azimuth-mean radial profile; (d)‒(f) (g)‒(i) fitting process and data of PMMA, PS particles with a diameter of 5 μm, all scales are 20 μm

Fig. 7. Image of shaped particle and illustration of shaped particle refractive index measurement. (a)‒(d) Original image of 5 μm diameter ellipsoidal Silica particle, numerical fitting of Lorenz-Mie theory and azimuth-mean radial profile; (e)‒(h) original image, fitting process, and data of 5 μm nearly diamond shaped PS particles, all scales are 20 μm

Fig. 8. Two-dimensional scatter plots of mass density and refractive index of PS, PMMA, PMSQ, and Silica particles, as well as density and refractive index histograms of four particles