Income Taxes - Deferred tax assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 20,564	$ 22,068
Inventory	462	287
Accruals	366	863
Depreciation and amortization	9	13
Research and experimental credits	3,995
Research and experimental expenditures	6,412	4,728
Stock-based compensation	428	268
Right of use liability	1,045	1,245
Gross deferred tax assets	33,281	29,472
Valuation allowance	(31,343)	(27,748)	$ (30,328)
Deferred tax assets	1,938	1,724
Deferred tax liabilities:
Right of use asset	(1,024)	(1,226)
Other	(646)	(348)
Deferred tax liabilities	(1,670)	(1,574)
Net deferred tax assets	268	150
Increase in valuation allowance	$ 3,595	$ (2,580)