INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carry-forward	$ 24,859	$ 18,498	$ 14,996
Inventory	104	115	52
Stock-based compensation	1,326	1,099	1,049
Start-up expenditures	177	199	221
Research and development credit carryforward	1,192	1,171	1,209
Accrued bonus	411	423	200
Severance liability	50	122	134
Unrealized loss on investments	1,366	371	40
Operating lease obligations	365	52	127
Capital loss on investment	107
Other	18	18	22
Total deferred tax assets	29,975	22,068	18,050
Deferred tax liabilities:
Machinery and equipment	(254)	(237)	(239)
Patents and trademarks	(373)	(358)	(351)
Gain on investment		(13)	(104)
Accrued expense		(24)	(51)
Operating lease right-of-use assets	(362)	(52)	(126)
Other intangible assets	(259)	(224)	(189)
Total deferred tax liabilities	(1,248)	(908)	(1,060)
Valuation allowance	(28,779)	(21,198)	$ (16,990)
Net deferred taxes	$ (52)	$ (38)