Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities:
Net loss	$ (5,221)	$ (4,568)
Adjustments to reconcile net loss to cash flows used in operating activities:
Depreciation and amortization	126	65
Stock-based compensation expense, net	355	380
Loss on disposal of property and equipment	0	46
Changes in operating assets and liabilities:
Accounts receivable	(14)	72
Inventories	(89)	(398)
Other current assets	(132)	20
Other assets and liabilities	24	67
Accounts payable and accrued expenses	(431)	(1,179)
Net cash used in operating activities	(5,382)	(5,495)
Investing Activities:
Purchases of property and equipment	(56)	(17)
Net cash used in investing activities	(56)	(17)
Financing Activities:
Proceeds from public stock offerings, net	18,902	9,616
Proceeds from warrant exercises	1	289
Payments on finance lease liability	(6)	0
Net cash provided by financing activities	18,897	9,905
Effect of exchange rate changes on cash	(3)	(3)
Net increase in cash and cash equivalents	13,456	4,390
Cash and cash equivalents - beginning of period	14,437	1,279
Cash and cash equivalents - end of period	27,893	5,669
Supplemental cash flow information
Inventory transferred to property, plant and equipment	$ 89	$ 0