. Author manuscript; available in PMC: 2013 Jun 17.

Published in final edited form as: Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2009 Sep-Oct;1(5):568–581. doi: 10.1002/wnan.50

Table 1.

Classification of nanoporous membranes.

TYPE OF MATERIAL	PROPERTIES (Strength / Chemical Stability)	MATERIAL	FABRICATION METHOD	TYPE OF PORES Size/Distribution/Density/Morphology	COMMENTS
INORGANIC	Good / Very good	Anodic Al₂O₃, SiO₂	Anodization process	> 10 nm/Narrow/10¹⁰ cm⁻² / ordered, straight	Physical and chemical stability, better membrane performance with ordered pores
		Ceramics (Al₂O₃, SiO₂, ZrO₂, TiO₂)	Powder sintering	1 ~ 50 nm / Wide / tortuous
		Ceramics (Al₂O₃, SiO₂, ZrO₂, TiO₂)	Sol-Gel	> 2 nm / narrow / 10¹⁰ cm⁻² / tortuous
		Si, SiC, other semiconductors	micromachining	> 10 nm / narrow / 10⁹ cm⁻² / ordered
ORGANIC	Fair / Poor - Fair	Polymers (PC, PE)	Ion-track etching	> 20 nm / narrow / 10⁸ cm⁻² / ordered	Low cost, fairly good biocompatibility
		Polymers (PC, PE, PET, PS)	Lithography
		Polymers (PC, PE, PET, PS)	Phase separation	>100 nm / medium / high / tortuous
COMPOSITE	Good / Good	Carbon / Metal / Metal oxide coated AAO	Chemical vapor or atomic layer deposition	Pore morphology and density same as support membranes or as defined by the process	Superior biocompatibility, strength narrower pore sizes with coating, additional functionality
		Oxide + Polymer (Eg: Nafion+TiO2)	Sol-gel / Solution Casting
		Coating polymer on support membrane	Layer by layer deposition	Pore size can be brought down to several nanometers by pore-filling coating