Note 10 - Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2021

Notes Tables

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Three Months Ended March 31,
	2021		2020
Cost of goods sold	$	5,000	$	--
Sales, general and administrative		216,000		52,000
Research and development		37,000		15,000
	$	258,000	$	67,000

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of Shares		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life		Aggregate Intrinsic Value
Outstanding at December 31, 2020		889,636	$	8.57
Forfeited		--
Outstanding at March 31, 2021		889,636		8.57		8.5	$	--
Vested and expected to vest at March 31, 2021		631,053	$	9.54		8.3	$	--
Exercisable at March 31, 2021		230,836	$	15.21		7.2	$	--

Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]

	Number of Shares		Weighted-Average Exercise Price Per Share		Weighted- Average Remaining Contract Term
Balance at December 31, 2020		1,116,484	$	37.27		0.49
Warrants expired		463,236
Warrants exercised		--	$	--
Outstanding at March 31, 2021		653,248	$	6.97		2.20
Exercisable at March 31, 2021		653,248	$	6.97		2.20