Summary of significant accounting policies (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Deferred Revenue, Current	$ 464,206	$ 309,638
Deferred Revenue, Revenue Recognized	2,460,013	1,357,852
Inventory Write-down	$ 1,171,456	$ 1,109,702
Statute of Limitations Extension Description	The statute of limitations is extended to five years under special circumstances, where the underpayment of taxes is more than RMB100,000. In the case of transfer pricing issues, the statute of limitation is ten years.
Operating Lease, Right-of-Use Asset	$ 5,700,000
Operating Lease, Liability	$ 5,900,000
Supplier Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration Risk, Percentage	10.70%
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration Risk, Percentage		10.10%