Note 5 - Stockholders' Equity and Common Stock Warrants (Details Textual) - USD ($)	1 Months Ended	9 Months Ended
	Feb. 28, 2021	Sep. 30, 2021	Sep. 30, 2020
Class of Warrant or Rights, Expired (in shares)		53,570
Class of Warrant or Right, Exercised During Period (in shares)		4,230,000
Proceeds from Warrant Exercises		$ 2,201,450	$ 8,046,103
Underwriter Warrants in Connection with the February 2021 Common Stock Offering [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	1,682,927
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 1.28125	$ 1.28
Warrants and Rights Outstanding, Term (Year)	5 years
Public Offering, Inclusive of Underwriter Shares [Member]
Stock Issued During Period, Shares, New Issues (in shares)	33,658,538
Shares Issued, Price Per Share (in dollars per share)	$ 1.025
Underwriter Option to Purchase Additional Shares, Term (Day)	30 days
Proceeds from Issuance of Common Stock	$ 31,100,000