Goodwill and intangible assets (Tables)

3 Months Ended

Mar. 31, 2017

Goodwill and intangible assets

Schedule of changes in carrying amount of goodwill

Goodwill, gross, as of December 31, 2016	$	276,786
Impact of change in Euro exchange rate		4,149
Accumulated impairment losses as of March 31, 2017		—
Goodwill, net, as of March 31, 2017	$	280,935

Schedule of the gross book value, accumulated amortization and amortization periods of intangible assets

	As of March 31, 2017						As of December 31, 2016						Amortization
	Gross book		Accumulated		Net book		Gross book		Accumulated		Net book		period
	value		amortization		value		value		amortization		value		(in years)
Trademarks and patents	$	1,208,510	$	(577,748)	$	630,762	$	1,203,097	$	(557,794)	$	645,303	15	-	21
Technology		2,339,577		(2,271,654)		67,923		2,305,019		(2,122,848)		182,171		5
Intangible assets, net	$	3,548,087	$	(2,849,402)	$	698,685	$	3,508,116	$	(2,680,642)	$	827,474

Schedule of amortization expense related to intangible assets

	Three Months Ended
	March 31,
	2017		2016
Amortization expense	$	136,427	$	142,138