Property and equipment (Details) (USD $)	Jun. 30, 2012		Dec. 31, 2011
Property and equipment [Line Items]
Property and equipment, gross	$ 2,994,684		$ 2,683,884
Less accumulated depreciation	(2,045,964)		(1,814,473)
Property and equipment, net	948,720		869,411
Leasehold Improvements [Member]
Property and equipment [Line Items]
Property and equipment, gross	978,550		925,086
Lab and clean room equipment [Member]
Property and equipment [Line Items]
Property and equipment, gross	1,660,399	[1]	1,463,144	[1]
Furniture and office equipment [Member]
Property and equipment [Line Items]
Property and equipment, gross	$ 355,735	[1]	$ 295,654	[1]

[1] The table above includes reclassifications of production equipment previously included in the furniture and office equipment category.