Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (13,634)	$ (26,483)
Adjustments to reconcile net loss to net cash used in operations:
Depreciation and amortization	963	1,649
Impairment of intangible assets	0	160
Impairment of property and equipment	0	434
Gain on disposal of property and equipment	(450)	0
Share-based compensation expense	1,297	1,569
Non-cash interest expense	11	0
Inventory write-downs	168	2,203
Change in:
Accounts receivable	1,079	(603)
Costs and estimated earnings in excess of billings on uncompleted contracts	0	987
Inventory	24	(1,286)
Other current and non-current assets	154	1,911
Accounts payable	(1,387)	(268)
Accrued liabilities	(1,550)	(3,379)
Deferred revenue	(21)	21
Contract liabilities and other currrent liabilities	(2,073)	(316)
Operating lease liabilities	(656)	(642)
Net cash used in operating activities	(16,075)	(24,043)
Cash flows from investing activities
Proceeds on sale of property and equipment	525	0
Purchases of property and equipment	(402)	(745)
Net cash provided by used in investing activities	123	(745)
Cash flows from financing activities
Principal payments under finance leases	(29)	(20)
Proceeds from long-term debt	1,571	0
Net proceeds from issuance of common stock	25,435	16,879
Net cash provided by financing activities	26,977	16,859
Change in cash and cash equivalents, and restricted cash	11,025	(7,929)
Cash, cash equivalents and restricted cash at beginning of period	6,272	14,201
Cash, cash equivalents and restricted cash at end of period	17,297	6,272
Supplemental schedule of non-cash investing and financing activities
Issuance of common stock for subscriptions receivable	6,135	0
Property and equipment acquired under finance leases	70	0
Non-cash additions to property and equipment	116	37
Issuance of common stock for commitment fee	$ 0	$ 535