
282 CHAPTER 11 Fabrication of hydrogel micropatterns
monocrystalline lm on a monocrystalline substrate. Epitaxial lms may be grown
from gaseous or liquid precursors [10].
11.2.1.4 Subtractive microfabrication
Subtractive microfabrication techniques employ removal or etching of a portion
of substrate to fabricate microstructures/patterns. Dry etching and wet etching are
two types of subtractive microfabrication techniques. (i) Dry etching refers to the
removal of material, typically a masked pattern of semiconductor material by expos-
ing the material to a bombardment of ions (usually plasma of reactive gases such
as uorocarbons, oxygen, chlorine, ...