Morphological examination of GAXA spheres was
performed by a Cambridge-Stereoscan model S 4-10
scanning electron microscope. The dry spheres were
attached to the sample holder and coated for 2 min
with a thin layer of gold (Z 24 nm) using an Anatech-
Hummer model 7 coating unit. The specimens were
viewed at an accelerating voltage of 2.0 kV.