Hydrophilic and Hydrophobic

One of the important characteristics in membrane selection is whether you want a membrane that is Hydrophobic or Hydrophilic. Here we'll define these terms, as well as provide some examples of membrane materials and applications for both types. 

Hydrophilic literally means “water loving.” Hydrophilic membranes will attract water, and in the process push away other molecules in order to allow water access to the membrane. This keeps contaminants away from the membrane allowing it stay clean and functioning for a longer period of time. Because of this trait hydrophilic membranes are especially well suited for medical applications and biological assays.

Hydrophobic on the other hand, literally means “afraid of water.” These membranes will block the passage of water and are commonly used for applications involving separation of water from other materials, such as venting gases.

Here is a helpful table that compares membrane materials and common uses for hydrophilic and hydrophobic properties:

	Hydrophilic	Hydrophobic
Materials	Silver Metal Polyethersulfone (PES) Glass Fiber Polycarbonate Track Etch (PCTE) (*When coated with PVP) Polyester (PETE) Mixed Cellulose Esters (MCE) Nylon Cellulose Acetate	Polypropylene Teflon (PTFE) - Laminated or unlaminated Polycarbonate Track Etch (*When not coated with PVP)
Applications	Sterilization or clarification of aqueous and organic solvent solutions Medical assays Bacterial removal Protein arrays Drug filtration IV filters HPLC sample preparation	Venting applications Protecting gas sensors from moisture or heavy particulates CO2 monitors Sterile process gases Filtration of strong acids and aggressive solutions Phase separations HPLC sample preparation requiring low detection levels