Note 11 - Warrant Liability Change in Fair Value During Year 2018 (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Product Warranty Liability [Table Text Block]

	Year Ended December 31,
	2019		2018
Fair value, beginning of period	$	—	$	2,462,859
Issuance of warrants		—		—
Change in fair value		—		(277,715	)
Transfer to additional paid-in capital		—		(2,185,144	)
Fair value, end of period	$	—	$	—