Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($)	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 9,431,000	$ 19,162,000
Accounts receivable, net of allowance for doubtful accounts of $5 and $66 as of June 30, 2022 and December 31, 2021, respectively	801,000	549,000
Inventory	1,599,000	1,472,000
Prepaid expenses and other current assets	1,407,000	1,055,000
Total current assets	13,238,000	22,238,000
Property and equipment, net	1,114,000	1,554,000
Investment in unconsolidated limited liability company	0	577,000
Other assets	1,136,000	1,544,000
Total assets	15,488,000	25,913,000
Current liabilities:
Accounts payable	904,000	1,480,000
Accrued liabilities	3,655,000	3,053,000
Note payable, current portion	5,453,000	0
Total current liabilities	10,012,000	4,533,000
Note payable, noncurrent portion	0	5,124,000
Other noncurrent liabilities	200,000	1,190,000
Total liabilities	10,212,000	10,847,000
Commitments and contingences (Note 9)
Stockholders’ equity:
Additional paid-in capital	258,813,000	256,918,000
Accumulated deficit	(253,538,000)	(241,853,000)
Total stockholders’ equity	5,276,000	15,066,000
Total liabilities and stockholders’ equity	15,488,000	25,913,000
Series B Preferred Stock [Member]
Stockholders’ equity:
Convertible preferred stock	$ 0	$ 0