Income taxes, Income Tax Provision (Benefit) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income taxes [Abstract]
Undistributed earnings of foreign subsidiaries	$ 0	$ 0
Percentage of federal statutory income tax rate	21.00%	21.00%
Tax expense (benefit) at statutory rate	$ (5,718,000)	$ (6,498,000)
Increase (reduction) in income taxes resulting from [Abstract]
State income taxes (benefits), net of federal benefit	(837,000)	(913,000)
Non-deductible gain on warrant adjustment valuation	417,000	670,000
Income from foreign subsidiaries	0	2,000
Change in valuation allowance	5,903,000	6,383,000
Registration penalties	354,000	0
Other	(91,000)	356,000
Income tax expense (benefit)	$ 28,000	$ 0