Figure 12.

(A) An illustration of the apparatus used to demonstrate ultrasound imaging of MPs. PE bags were filled with suspensions of several types of MPs in tap water, and an ultrasound probe was applied to the outer surface of the bag to image its contents. (B) An image captured by the ultrasound machine system of PE MPs ranging from 125 $\mathsf{\mu }$$\mathrm{m}$ to 150 $\mathsf{\mu }$$\mathrm{m}$ in diameter.