4. Other classification criteria

In addition to the above classification criteria, some surfactants are also named after their sources, such as biosurfactants, which refer to surfactants directly extracted from animals and plants, or obtained through biotechnology such as fermentation. Some surfactants are named because their hydrophilic groups are a certain type of organic compounds, such as amino acid surfactants, alkyl glycosides and peptide surfactants. These surfactants are favored by people in life sciences, daily chemicals, washing, skin care, etc. due to their high biocompatibility. In addition, there are other classification standards, such as classifying surfactants into small molecule surfactants and high molecule surfactants according to molecular weight, etc.