Note 8 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Stock-based compensation expense	$ 278,130	$ 297,280	$ 556,261	$ 478,560
Research and Development Expense [Member]
Stock-based compensation expense	58,892	59,567	117,785	92,567
General and Administrative Expense [Member]
Stock-based compensation expense	$ 219,238	$ 237,713	$ 438,476	$ 385,993