Note 13 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets
Net operating loss carryforwards and credits	$ 20,698	$ 15,064
Share-based compensation expense	3,813	3,441
Property, plant and equipment	725	1,025
Common stock warrant liabilities	0	524
Operating lease liabilities	91	147
Other	54	21
Less: valuation allowance	(22,669)	(19,802)
Total deferred tax assets	2,712	420
Deferred tax liabilities
Common stock warrant liabilities	(1,129)	0
Operating lease Right-of-use assets	(1,583)	(420)
Total deferred tax liabilities	(2,712)	(420)
Net deferred tax assets (liabilities)	$ 0	$ 0