Income Taxes - Deferred tax assets (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Deferred tax assets
Net operating loss carryforwards	$ 66,265	$ 61,427
Capitalized research and development expenses	6,185	4,845
Stock-based compensation	1,604	2,300
Accrued expenses and other	1,193	1,235
Lease liability	478	557
Research and development credits	830	830
Inventory reserve	432	289
Interest expense carryforward	691	523
Gross deferred tax asset before valuation allowance	77,678	72,006
Less: valuation allowance	(76,782)	(71,086)
Total deferred tax asset	896	920
Deferred tax liabilities
Depreciation and amortization	(326)	(436)
Right of use asset	(430)	(484)
Gross deferred tax liability	(756)	(920)
Less: valuation allowance	(76,782)	(71,086)
Net deferred tax asset	$ 140	$ 0