Note 4 - Lincoln Park Financing (Details Textual) - Lincoln Park Capital Fund, LLC [Member] - USD ($)		12 Months Ended
	Aug. 25, 2017	Dec. 31, 2018	Dec. 31, 2017
Stock Purchase Agreement, Maximum Amount of Common Stock	$ 10,000,000
Stock Purchase Agreement, Maximum Shares of Common Stock to be Sold in a Single Business Day, Tier One	50,000
Stock Purchase Agreement, Maximum Shares of Common Stock to be Sold in a Single Business Day, Tier Two	75,000
Stock Purchase Agreement, Maximum Shares of Common Stock to be Sold in a Single Business Day, Tier Three	100,000
Stock Purchase Agreement, Maximum Shares of Common Stock to be Sold in a Single Business Day, Tier Four	200,000
Stock Purchase Agreement, Maximum Value of Total Common Stock to be Sold in a Single Business Day	$ 500,000
Stock Issued During Period, Shares, New Issues	488,998	2,891,749	1,199,991
Pro Forma Information, Stock Purchase Agreement, Stock Purchase Requested	$ 25,000
Pro Forma Information, Stock Purchase Agreement, Stock Purchase Requested, Additional Commitment Common Stock Issued	1,222
Pro Forma Information, Stock Purchase Agreement, Additional Commitment Shares, Numerator Value of Total Shares Calculation	$ 25,000
Pro Forma Information, Stock Purchase Agreement, Additional Commitment Shares, Denominator Value of Total Shares Calculation	$ 10,000,000
Pro Forma Information, Stock Purchase Agreement, Additional Commitment Shares, Multiplier of Total Shares Calculation	488,998
Maximum [Member]
Stock Purchase Agreement, Share Price, Tier One	$ 0.50
Stock Purchase Agreement, Share Price, Tier Two	0.74
Stock Purchase Agreement, Share Price, Tier Three	1.24
Minimum [Member]
Stock Purchase Agreement, Share Price, Tier Two	0.50
Stock Purchase Agreement, Share Price, Tier Three	0.75
Stock Purchase Agreement, Share Price, Tier Four	$ 1.25