Income taxes - Reconciliation of Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax credit at the federal and state statutory rate	$ (3,854,992)	$ (2,219,152)
Foreign taxation	(62,163)	121,579
Permanent differences	1,569,469	1,280,902
Foreign net operating losses utilized		(19,347)
Foreign tax rate differential	1,173
Valuation allowance	2,346,513	938,250
Net future tax asset	$ 0	$ 102,232