CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (10,489)	$ (8,382)
Adjustments to reconcile net loss to net cash flows used in operating activities:
Share-based compensation	3,998	3,244
Depreciation	860	1,161
Amortization of intangible assets	172	239
Amortization of deferred financing costs	112	415
Non-cash lease expenses	295	237
Accretion of asset retirement obligation	22	17
(Gain) loss on fixed asset disposal	(15)	236
Increase (decrease) in cash resulting from changes in:
Accounts receivable	2,679	3
Inventory	(1,781)	(1,221)
Prepaid expenses	11	910
Income taxes	63	54
Other assets	(298)	319
Accounts payable	456	(936)
Accrued compensation	(6,494)	(2,314)
Accrued expenses	550	(484)
Other liabilities	(364)	(177)
Net cash flows used in operating activities	(10,223)	(6,679)
Cash flows from investing activities:
Purchases of equipment	(118)	(1,941)
Patent application costs	(54)	(153)
Principal payments from note receivable	0	15
Principal payments from note receivable	24	0
Net cash flows used in investing activities	(148)	(2,079)
Cash flows from financing activities:
Stock repurchased for tax withholdings on vesting of restricted stock	(1,191)	(3,216)
Proceeds from exercise of stock options	166	915
Principal payments on finance lease	(11)	(7)
Net cash flows used in financing activities	(1,036)	(2,308)
Net change in cash	(11,407)	(11,066)
Cash and cash equivalents, beginning of period	87,083	95,812
Cash and cash equivalents, end of period	$ 75,676	$ 84,746