Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts receivable, allowance for doubtful accounts	$ 49	$ 124	[1]
Convertible preferred stock, shares authorized (in shares)	10,000,000	10,000,000	[1]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001	[1]
Common stock, shares authorized (in shares)	75,000,000	75,000,000	[1]
Common stock, shares issued (in shares)	10,602,560	2,171,316	[1]
Common stock, shares outstanding (in shares)	10,602,560	2,171,316	[1]
Series B Preferred Stock [Member]
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001	[1]
Convertible preferred stock, shares issued (in shares)	39,279	35,819	[1]
Convertible preferred stock, shares outstanding (in shares)	39,279	35,819	[1]
Series C Preferred Stock [Member]
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares issued (in shares)	0	0
Convertible preferred stock, shares outstanding (in shares)	0	0

[1] The condensed consolidated balance sheet as of December 31, 2020 has been derived from the audited consolidated financial statements as of that date.