Note 8 - Stockholders' Equity (Details Textual) - USD ($)									12 Months Ended
	Dec. 31, 2021	Dec. 21, 2021	Apr. 07, 2021	Feb. 11, 2021	Dec. 18, 2020	Oct. 28, 2020	Oct. 21, 2020	Jul. 23, 2020	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2020
Common Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001			$ 0.001		$ 0.001	$ 0.001
Proceeds from Issuance or Sale of Equity, Total			$ 37,300,000
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)									$ 2.40	$ 2.40	$ 5.14
Preferred Stock, Shares Issued, Total (in shares)									280,898	280,898
Equity Securities, Notice of Deficiency, Failure to Maintain Minimum Bid Price, Amount (in dollars per share)		$ 1.00
Equity Securities, Minimum Closing Bid Price (in dollars per share)	$ 1.00	$ 1.00
Equity Securities, Threshold Consecutive Trading Days (Day)	10 days	10 days
HCWainwrightCoLLC [Member]
Shares Issued, Price Per Share (in dollars per share)			$ 1.395
Percentage of Underwriting Discount, Price Per Share			7.00%
Stock Issued During Period, Option to Purchase Additional Shares, Term (Day)			30 days
The “Placement Agent’s Warrants No. 1” [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)								469,565
Percentage of Shares Sold in Offering								6.00%
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)								$ 2.875
Percentage of Per Share Offering Price of Shares								125.00%
Class of Warrant or Right, Fair Value Price (in dollars per share)								$ 2.01
The “Placement Agent’s Warrants No. 2” [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)						173,274
Percentage of Shares Sold in Offering						6.00%
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)						$ 2.6875
Percentage of Per Share Offering Price of Shares						125.00%
Class of Warrant or Right, Fair Value Price (in dollars per share)						$ 1.80
The “Placement Agent’s Warrants No. 3” [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				170,732
Percentage of Shares Sold in Offering				6.00%
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)				$ 4.0625
Percentage of Per Share Offering Price of Shares				125.00%
Class of Warrant or Right, Fair Value Price (in dollars per share)				$ 2.94
The “Underwriter Warrants” [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)			1,493,150
Percentage of Shares Sold in Offering			6.00%
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)			$ 1.875
Underwritten Public Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)			21,639,851
Shares Issued, Price Per Share (in dollars per share)			$ 1.50
Over-Allotment Option [Member]
Stock Issued During Period, Shares, New Issues (in shares)			3,245,977
The “Wainwright ATM Agreement” [Member] | Maximum [Member]
Common Stock Issuable, Aggregate Offering Price					$ 3,582,614
Common Stock [Member] | The “Public Offering Shares” [Member]
Stock Issued During Period, Shares, New Issues (in shares)							7,826,086
Shares Issued, Price Per Share (in dollars per share)							$ 2.30
Proceeds from Issuance or Sale of Equity, Total							$ 18,000,000.0
Common Stock [Member] | The “October Registered Offering” [Member]
Stock Issued During Period, Shares, New Issues (in shares)						2,887,906
Shares Issued, Price Per Share (in dollars per share)						$ 2.15
Proceeds from Issuance or Sale of Equity, Total						$ 6,200,000
Common Stock [Member] | The “February Registered Offering” [Member]
Stock Issued During Period, Shares, New Issues (in shares)				2,845,535
Shares Issued, Price Per Share (in dollars per share)				$ 3.25
Proceeds from Issuance or Sale of Equity, Total				$ 9,250,000
Common Stock [Member] | The “Wainwright ATM Agreement” [Member]
Stock Issued During Period, Shares, New Issues (in shares)					1,139,323
Proceeds from Issuance or Sale of Equity, Total					$ 3,600,000
Shares Issued, Weighted Average Price Per Share (in dollars per share)					$ 3.14
Series D Preferred Stock [Member]
Preferred Stock, Shares Issued, Total (in shares)									280,898
Preferred Stock, Conversion Basis									1