Intangible assets other than goodwill - Narrative (Details) - USD ($)		12 Months Ended
	May 18, 2017	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense		$ 99,310	$ 98,310
Net credit to cost of sales related to the amortization of contract related assets and liabilities		526,719	0
Fair Value, Benchmark Level of Margin Contribution, Percent	35.00%
Product Certifications
Acquired Finite-Lived Intangible Assets [Line Items]
Capitalized finited lived intangible assets		61,053	30,035
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Capitalized finited lived intangible assets		$ 181,637	77,240
Patents \| Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Finited lived intangible assets, estimated useful life		7 years
Patents \| Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Finited lived intangible assets, estimated useful life		10 years
Trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Capitalized finited lived intangible assets		$ 2,375	$ 12,390