Amortizable intangible assets -Amounts related to intangible assets (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 1,277,511	$ 1,230,274
Finite-Lived Intangible Assets, Accumulated Amortization	(242,257)	(218,974)
Finite-Lived Intangible Assets, Net	1,035,254us-gaap_FiniteLivedIntangibleAssetsNet	1,011,300us-gaap_FiniteLivedIntangibleAssetsNet
Intangible Assets, Current	1,035,254us-gaap_IntangibleAssetsCurrent
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	550,335	514,930
Finite-Lived Intangible Assets, Accumulated Amortization	69,446	62,242
Finite-Lived Intangible Assets, Net		452,688
Intangible Assets, Current	480,889
Product Certification [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	487,176	475,344
Finite-Lived Intangible Assets, Accumulated Amortization	140,811	128,732
Finite-Lived Intangible Assets, Net		346,612
Intangible Assets, Current	346,365
Developed Technology Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	240,000	240,000
Finite-Lived Intangible Assets, Accumulated Amortization	32,000	28,000
Finite-Lived Intangible Assets, Net		212,000
Intangible Assets, Current	$ 208,000