Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 37,902	$ 41,309
Restricted cash	5	5
Trade accounts receivable, net of allowance for doubtful accounts	64	157
Inventory	589	391
Prepaid expenses and other current assets	209	326
Total current assets	38,769	42,188
Property and equipment, net	12,054	12,465
Patents and trademarks, net	365	408
Other assets	14	14
Total assets	51,202	55,075
Current liabilities:
Accounts payable	65	92
Accrued liabilities	237	365
Deferred revenue		7
Total current liabilities	302	464
Long-term liabilities:
Other long-term liabilities	856	856
Total liabilities	3,342	3,512
Shareholders' equity:
Preferred Stock, $0.001 par value; 10,000,000 shares authorized; 0 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	0	0
Common stock, $0.001 par value; 1,100,000,000 shares authorized; 909,239,009 and 908,768,116 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	909	909
Warrants	18,179	18,179
Additional paid-in capital	278,518	277,924
Accumulated deficit	(249,673)	(245,376)
Non-controlling interest in subsidiary	(73)	(73)
Total shareholders' equity	47,860	51,563
Total liabilities and shareholders' equity	51,202	55,075
Warrant [Member]
Long-term liabilities:
Warrant liabilities, long-term	$ 2,184	$ 2,192