Note 9 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	2018			2017			2016
Weighted average risk-free interest rates		2.79	%		2.40	%		2.26	%
Expected dividend yield		0.0	%		0.0	%		0.0	%
Expected life of option (in years)		7.0			7.0			7.0
Expected volatility		71.34	%		89.73	%		88.72	%

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	2018		2017		2016
General and administrative expense	$	113,306	$	31,271	$	31,191
Research and development expense		41,998		25,953		23,614
Total stock option expense	$	155,304	$	57,224	$	54,805

Share-based Compensation, Stock Options, Activity [Table Text Block]

	2018		2017		2016
Weighted average fair value of options granted	$	0.02	$	0.04	$	0.05
Intrinsic value of options exercised		-		-		-
Total fair value of options vested		153,838		58,337		54,757