Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (22,027,000)	$ (21,915,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts	125,000	454,000
Depreciation and amortization	1,123,000	1,295,000
Stock-based compensation	3,779,000	2,651,000
Non-cash interest expense	606,000	535,000
Loss from minority interest in limited liability company	256,000	383,000
Loss on disposal of property and equipment	113,000	20,000
Modification of warrants	373,000	1,838,000
Forgiveness of Paycheck Protection Program loan	(1,358,000)	0
Changes in assets and liabilities:
Accounts receivable	96,000	349,000
Inventory	2,207,000	1,360,000
Prepaid expenses and other current assets	(24,000)	151,000
Other noncurrent assets	320,000	461,000
Accounts payable	599,000	(727,000)
Accrued and other liabilities	553,000	(2,422,000)
Other noncurrent liabilities	365,000	331,000
Net cash used in operating activities	(12,878,000)	(15,234,000)
Cash flows from investing activities:
Purchase of property and equipment	(456,000)	(781,000)
Net cash used in investing activities	(456,000)	(781,000)
Cash flows from financing activities:
Proceeds from January 2021 Offering, net of issuance costs	25,122,000	0
Proceeds from exercise of common warrants	179,000	8,407,000
Transaction costs in connection with 2020 Warrant Offering	0	(334,000)
Proceeds from purchase of common shares under Purchase Agreement with LPC	704,000	341,000
Proceeds from Paycheck Protection Program loan	0	1,343,000
Proceeds from issuance of common shares from employee stock purchase plan	38,000	0
Net cash provided by financing activities	25,973,000	9,230,000
Net increase (decrease) in cash and cash equivalents	12,639,000	(6,785,000)
Cash and cash equivalents - beginning of period	6,523,000	13,308,000
Cash and cash equivalents - end of period	19,162,000	6,523,000
Supplemental disclosure:
Cash paid for interest	0	0
Cash paid for income taxes	0	0
Supplemental disclosure of cash flow information as of end of period:
Forgiveness of Paycheck Protection Program loan	1,358,000	0
Issuance of Series B convertible preferred stock in settlement of dividends	4,685,000	4,141,000
Issuance of note payable in settlement of accrued interest	602,000	532,000
Net transfer of equipment between inventory and property and equipment	(425,000)	247,000
Operating cash outflows from operating leases	195,000	303,000
Purchase Agreement with LPC [Member]
Cash flows from financing activities:
Transaction costs	(70,000)	(494,000)
November 2019 Offering [Member]
Cash flows from financing activities:
Transaction costs	$ 0	$ (33,000)