Note 3 - Sale of Stock for Cash (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Proceeds from Issuance of Common Stock			$ 3,267,000	$ 4,120,000
Warrants Issued with 2020 Unit Offering [Member] | Maximum [Member]
Warrants and Rights Outstanding, Term (Year)	5 years		5 years
The 2020 Unit Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)	3,766,126	388,889	13,568,524	3,820,436
Proceeds from Issuance of Common Stock	$ 632,000	$ 70,000	$ 2,364,000	$ 575,000
Lincoln Park Capital Fund, LLC [Member]
Stock Issued During Period, Shares, New Issues (in shares)	2,440,958	2,917,819	4,353,919	21,444,128
Proceeds from Issuance of Common Stock	$ 485,000	$ 530,000	$ 903,000	$ 3,545,000