The surface morphology and shape of the cross-section can be observed via scanning electron microscope (SEM) imaging after removal of solvent. Also, environmental scanning electron microscope (ESEM) can be used to observe wet hydrogel fibers. But different treatments will affect the surface morphology of the hydrogel fiber drastically. If the hydrogel fiber was dried directly, a smooth surface would be obtained because of the collapse of the polymer network after the removal of the solvent.  If the hydrogel fiber was lyophilized, a porous surface will usually be found due to the pore-forming effect of the ice crystal. ESEM can directly observe the surface morphology. The resulting image usually indicates a smooth surface with some wrinkled formed due to the gradual loss of water.