Property, plant and equipment, net (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation	$ 5,823,572	$ 5,152,396
Property Plant And Equipment Deductions For Government Grants	75,584	263,948
Impairment of Long-Lived Assets to be Disposed of	569,120	0
Huizhou Facilities [Member]
Property, Plant and Equipment [Line Items]
Pledged Assets Not Separately Reported Property Plant And Equipment	8,536,246	9,224,694
Ganzhou Facilities [Member]
Property, Plant and Equipment [Line Items]
Pledged Assets Not Separately Reported Property Plant And Equipment	$ 353,752	$ 396,843