Note 8 - Stockholders' Equity - Stock Warrants Outstanding and Issuance (Details)	6 Months Ended
	Mar. 31, 2020 $ / shares shares
Stock Warrants Outstanding, Shares (in shares)	5,493,130
Director/Shareholder 1 [Member]
Stock Warrants Outstanding, Issue Date	May 12, 2015
Stock Warrants Outstanding, Shares (in shares)	240
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 1,000
Stock Warrants Outstanding, Expiration	May 12, 2020
Director/Shareholder 2 [Member]
Stock Warrants Outstanding, Issue Date	Dec. 31, 2015
Stock Warrants Outstanding, Shares (in shares)	120
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 1,000
Stock Warrants Outstanding, Expiration	Dec. 31, 2020
Placement Agent Stock Warrants 1 [Member]
Stock Warrants Outstanding, Issue Date	May 17, 2016
Stock Warrants Outstanding, Shares (in shares)	1,736
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 187.50
Stock Warrants Outstanding, Expiration	May 17, 2021
Placement Agent Stock Warrants 2 [Member]
Stock Warrants Outstanding, Issue Date	May 11, 2016
Stock Warrants Outstanding, Shares (in shares)	1,067
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 187.50
Stock Warrants Outstanding, Expiration	May 11, 2021
Placement Agent Stock Warrants 3 [Member]
Stock Warrants Outstanding, Issue Date	Jul. 15, 2016
Stock Warrants Outstanding, Shares (in shares)	880
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 230
Stock Warrants Outstanding, Expiration	Jul. 15, 2021
Investor Stock Warrants 1 [Member]
Stock Warrants Outstanding, Issue Date	Nov. 09, 2016
Stock Warrants Outstanding, Shares (in shares)	4,271
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 175
Stock Warrants Outstanding, Expiration	May 09, 2022
Director/Shareholder 3 [Member]
Stock Warrants Outstanding, Issue Date	Dec. 31, 2016
Stock Warrants Outstanding, Shares (in shares)	120
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 1,000
Stock Warrants Outstanding, Expiration	Dec. 31, 2021
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	$ 132.50
Stock Warrants Outstanding, Expiration	Oct. 10, 2025
Director/Shareholder 4 [Member]
Stock Warrants Outstanding, Issue Date	Dec. 31, 2017
Stock Warrants Outstanding, Shares (in shares)	120
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 1,000
Stock Warrants Outstanding, Expiration	Dec. 31, 2021
Investor Stock Warrants 2 [Member]
Stock Warrants Outstanding, Issue Date	Oct. 19, 2018
Stock Warrants Outstanding, Shares (in shares)	3,120
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 25
Stock Warrants Outstanding, Expiration	Oct. 19, 2023
Placement Agent Stock Warrants 4 [Member]
Stock Warrants Outstanding, Issue Date	Oct. 16, 2018
Stock Warrants Outstanding, Shares (in shares)	10,000
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 31.25
Stock Warrants Outstanding, Expiration	Oct. 16, 2023
Investor Stock Warrants 3 [Member]
Stock Warrants Outstanding, Issue Date	Mar. 12, 2019
Stock Warrants Outstanding, Shares (in shares)	159,236
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 4
Stock Warrants Outstanding, Expiration	Oct. 19, 2023
Investor Stock Warrants 4 [Member]
Stock Warrants Outstanding, Issue Date	Mar. 12, 2019
Stock Warrants Outstanding, Shares (in shares)	2,556,875
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 4
Stock Warrants Outstanding, Expiration	Sep. 12, 2024
Investor Stock Warrants 5 [Member]
Stock Warrants Outstanding, Issue Date	Mar. 12, 2019
Stock Warrants Outstanding, Shares (in shares)	2,556,875
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 4
Stock Warrants Outstanding, Expiration	Sep. 12, 2021
Investor Stock Warrants 6 [Member]
Stock Warrants Outstanding, Issue Date	Mar. 12, 2019
Stock Warrants Outstanding, Shares (in shares)	69,295
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 0.05
Stock Warrants Outstanding, Expiration	Sep. 12, 2024
Placement Agent Stock Warrants 5 [Member]
Stock Warrants Outstanding, Issue Date	Mar. 12, 2019
Stock Warrants Outstanding, Shares (in shares)	127,848
Stock Warrants Outstanding, Price (in dollars per share) | $ / shares	$ 4
Stock Warrants Outstanding, Expiration	Sep. 12, 2024