208hr high resolution sputter coater

The microparticle geometry and size were determined using a field emission scanning electron microscopy (SEM) (S-4100T, Hitachi High Technologies America, Inc., Pleasanton, CA, USA). Particles were immobilized to a double-sided carbon tape (Ted Pella Inc, Redding, CA, USA) supported by an Al stub (Ted Pella Inc. Redding, CA, USA). After coating the particles with 10 nm of gold using a sputter coater (208 HR High Resolution Sputter Coater, Ted Pella Inc., Redding, CA, USA), the samples were transported to the SEM vacuum chamber. The typical acceleration voltage and emission current used in this work were 2 kV and 10 $\mathsf{\mu }$ A, respectively. The SEM images were loaded into Image J (National Institutes of Health, Bethesda, MD, USA), where the size of the microparticles was determined using the geometrical Feret diameter ( $d_g$ ).
The aerodynamic diameter ( $d_a$ ) was calculated using Equation (3), following published method [32 (link)]. The tapped density ( $\sigma$ ) was measured using established protocols [32 (link)], where the particle containers were tapped on a hard surface for 1000 taps. The reference density ( $\rho$ ) is 1 g/mL, which is the standard reference for the diameter of a spherical particles that has the same vertical velocity as the particle of interest [34 (link)].
$$d_a=d_g\sqrt{\frac{\sigma }{\rho }}$$

To analyze the surface of the luminal uterine epithelium, uteri were harvested from mice at 3.5 dpc and flushed with 0.5 ml of PBS to remove blastocysts and debris. The uteri were then dissected longitudinally under a dissecting microscope with spring scissors and immediately submerged in ice-cold 2.5% glutaraldehyde in PBS overnight at 4 °C. The tissues were washed extensively in PBS and gradually dehydrated in a series of EtOH solutions for 15 min incubation times and stored in 100% EtOH. The tissues were then dried in an Autosamdri-815 (Tousimis Research Corporation) critical point dryer for 1.5 h. To enhance the SEM image contrast, the samples were coated with a thin iridium film of 7 nm with a magnetron sputtering coater (208HR High Resolution Sputter Coater, Ted Pella, Inc). Images of the uterus were collected in a Nova Nano SEM (FEI) with a working distance of 5 mm at room temperature in a high vacuum (2E⁻⁶ Torr) at the Houston Methodist Hospital TEM Microscopy Core.