Note 6 - Equity Transactions (Details Textual)								1 Months Ended		3 Months Ended			6 Months Ended
	Jan. 01, 2021 USD ($) shares	Dec. 22, 2020 USD ($) shares	Dec. 22, 2020 USD ($)	Dec. 11, 2020 USD ($) $ / shares shares	Dec. 08, 2020 shares	Aug. 27, 2020 USD ($) $ / shares shares	Apr. 24, 2020 USD ($) $ / shares shares	Mar. 31, 2021 USD ($) shares	Jan. 31, 2021 USD ($) shares	Jun. 30, 2021 USD ($) $ / shares shares	Mar. 31, 2021 USD ($) shares	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2020 USD ($)	Jun. 24, 2021 shares	Dec. 31, 2020 shares
Common Stock, Shares Authorized (in shares)					10,000,000					20,000,000			20,000,000		20,000,000	20,000,000
Share-based Payment Arrangement, Expense | $										$ 0		$ 6,840	$ 0	$ 14,060
Proceeds from Issuance of Private Placement | $						$ 2,831,114
Share-based Payment Arrangement, Nonemployee [Member]
Stock Issued During Period, Shares, Issued for Services (in shares)									10,000
Stock Issued During Period, Value, Issued for Services | $									$ 50,300		$ 50,300
Warrants to Purchase Units Sold in May 2016 Private Placement [Member]
Warrants and Rights Outstanding, Term (Year)						7 years				7 years			7 years
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares										$ 25.00			$ 25.00
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)										4,800			4,800
Underwriter Warrants [Member] | Maxim Group LLC [Member]
Warrants and Rights Outstanding, Term (Year)				5 years
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares				$ 6.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				57,500
Class of Warrant or Right, Percentage of Shares Sold in Public Offering				2.00%
Warrants To Purchase Common Stock [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)										2,050,221			2,050,221
Class of Warrant or Right, Exercised During Period (in shares)	197,000
Proceeds from Warrant Exercises | $	$ 985,000
Warrants To Purchase Common Stock [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares										$ 5.00			$ 5.00
Warrants To Purchase Common Stock [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares										100.00			$ 100.00
Warrants Issued in Connection with December 2020 Public Offering [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)								1,519,984			1,519,984
Proceeds from Warrant Exercises | $								$ 7,599,920
Warrants Exercised in Net Share Settlement [Member]
Class of Warrant or Right, Exercised During Period (in shares)								9,436					78,220
Warrants Issued in Connection With December 2021 Public Offering [Member]
Proceeds from Warrant Exercises | $													$ 391,100
Warrants to Purchase Units Sold in February 2017 Private Placement [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares										$ 35.00			$ 35.00
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)										1,641			1,641
Warrants to Purchase Units Sold in October 2017 Private Placement [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares										$ 25.00			$ 25.00
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)										2,400			2,400
Private Placement [Member]
Stock Issued During Period, Shares, New Issues (in shares)							200,000
Shares Issued, Price Per Share (in dollars per share) | $ / shares						$ 10	$ 10
Proceeds from Issuance of Private Placement | $							$ 2,000,000
Equity Units Issued During Period, Shares, New Issues (in shares)						283,111
Equity Units, Number of Common Shares in Each Unit (in shares)						1
Private Placement [Member] | August 2020 Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)						1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares						$ 15
December 2020 Public Offering [Member]
Shares Issued, Price Per Share (in dollars per share) | $ / shares				$ 5.00
Equity Units Issued During Period, Shares, New Issues (in shares)				2,500,000
Equity Units, Number of Common Shares in Each Unit (in shares)				1
Proceeds from Issuance or Sale of Equity, Total | $		$ 14,375,000		$ 12,503,750
Underwriting Discounts and Commissions, Percent				8.00%
Payments of Stock Issuance Costs | $		$ 1,703,000
Underwriting Agreement [Member]
Equity Units, Number of Warrants in Each Unit				1
Underwriting Agreement [Member] | The Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares				$ 5.00
Over-Allotment Option [Member] | Maxim Group LLC [Member]
Stock Issued During Period, Shares, New Issues (in shares)		375,000
Purchase Agreement Optional Period to Shares (Day)				45 days
Purchase Agreement, Maximum, Additional Shares Available for Purchase During the Optional Period (in shares)				375,000
Over Allotment Options, Number of Shares for Warrants (in shares)				375,000
Proceeds from Issuance or Sale of Equity, Total | $			$ 1,871,250
Over-Allotment Option [Member] | The Warrants [Member] | Maxim Group LLC [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				375,000
Warrants Exercised in Net Share Settlement [Member]
Stock Issued During Period, Shares, Warrants Exercised (in shares)								2,913
Employees [Member]
Shares Issued, Shares, Share-based Payment Arrangement, before Forfeiture (in shares)									53,938
Shares Issued, Value, Share-based Payment Arrangement, before Forfeiture | $									$ 271,308
Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio					100