Note 8 - Stockholders' Equity - Stock Warrants Outstanding and Issuances (Details)	6 Months Ended
	Mar. 31, 2024 $ / shares shares
Stock Warrants Outstanding, Shares (in shares)	1,702,888
Financing Warrants [Member]
Stock Warrants Outstanding, Issue Date	Oct. 10, 2017
Stock Warrants Outstanding, Shares (in shares)	1,327
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 132.5
Stock Warrants Outstanding, Expiration	Oct. 10, 2025
Investor Stock Warrants 1 [Member]
Stock Warrants Outstanding, Issue Date	Mar. 12, 2019
Stock Warrants Outstanding, Shares (in shares)	872,625
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 4
Stock Warrants Outstanding, Expiration	Sep. 12, 2024
Investor Stock Warrants 2 [Member]
Stock Warrants Outstanding, Issue Date	Mar. 12, 2019
Stock Warrants Outstanding, Shares (in shares)	13,738
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 0.05
Stock Warrants Outstanding, Expiration	Sep. 12, 2024
Placement Agent Stock Warrants 1 [Member]
Stock Warrants Outstanding, Issue Date	Mar. 12, 2019
Stock Warrants Outstanding, Shares (in shares)	11,992
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 4
Stock Warrants Outstanding, Expiration	Sep. 12, 2024
Placement Agent Stock Warrants 2 [Member]
Stock Warrants Outstanding, Issue Date	Feb. 04, 2021
Stock Warrants Outstanding, Shares (in shares)	31,564
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 3.88
Stock Warrants Outstanding, Expiration	Feb. 04, 2026
Investor Stock Warrants 3 [Member]
Stock Warrants Outstanding, Issue Date	May 14, 2021
Stock Warrants Outstanding, Shares (in shares)	592,106
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 2.51
Stock Warrants Outstanding, Expiration	Nov. 16, 2026
Placement Agent Stock Warrants 3 [Member]
Stock Warrants Outstanding, Issue Date	May 14, 2021
Stock Warrants Outstanding, Shares (in shares)	179,536
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 2.85
Stock Warrants Outstanding, Expiration	May 12, 2026