Note 3 - Sale of Stock for Cash (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 13, 2022
Proceeds from Issuance of Common Stock	$ 800,000	$ 1,202,000
Warrants Issued with 2020 Unit Offering [Member] | Maximum [Member]
Warrants and Rights Outstanding, Term (Year)	5 years
Warrants Issued with 2020 Unit Offering [Member] | Minimum [Member]
Warrants and Rights Outstanding, Term (Year)	6 months
The 2020 Unit Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)	3,656,000	5,196,968
Proceeds from Issuance of Common Stock	$ 695,000	$ 856,000
Lincoln Park Capital Fund, LLC [Member]
Stock Purchase Agreement, Maximum Amount of Common Stock			$ 10,000,000
Stock Issued During Period, Shares, New Issues (in shares)	545,402	1,506,821
Proceeds from Issuance of Common Stock	$ 105,000	$ 346,000