Income Taxes - Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets (liabilities):
Net operating loss carryforwards	$ 33,640	$ 28,053
Common stock warrants	1,894	1,876
Foreign net operating loss carryforwards		134
174 capitalization	3,410
Stock-based compensation	2,411	1,584
Bonus accrual	202	100
R&D credit	500	500
Depreciation	(3)	(2)
Deferred tax assets	42,054	32,245
Valuation allowance	(42,054)	(32,245)
Deferred tax assets, net of allowance	$ 0	$ 0