Note 1 - Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

Property Plant and Equipment Useful Life [Table Text Block]

	Years
Computers and office equipment	3	-	7
Leasehold improvements (1)		5
Manufacturing tooling	3	-	7
Demo equipment		3
Laboratory equipment		4

Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]

	Three Months Ended March 31,
	2020			2019
	Stock Options
Expected dividend yield		0.0%			0.0%
Expected stock price volatility		82.6%			79.8%
Risk-free interest rate	0.70%	-	1.57%	2.41%	-	2.76%
Expected life (years)		10			10
	Warrants
Expected dividend yield		0.0%			0.0%
Expected stock price volatility		82.6%			79.8%
Risk-free interest rate	0.54%	-	0.79%	2.50%	-	2.58%
Expected life (years)	2	-	5.5		5