Note 9 - Collaboration and Device Development Payable (Tables)

12 Months Ended

Dec. 31, 2019

Series E Warrants [Member]

Notes Tables

Schedule of Assumptions Used for Warrant Valution [Table Text Block]

Significant Input Assumptions of Warrant Valuation
Historical volatility	103	%
Expected term (in years)	5
Risk-free interest rate	2.70	%