Note 11 - Income Taxes - Summary of Significant Components of Deferred Federal Income Taxes (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carryforwards	$ 10,761,000	$ 9,570,000
Tax credits	10,354,000	8,104,000
Impairment allowances	19,000	13,000
Stock-based compensation	45,000	0
Other	105,000	99,000
Accrued bonuses	245,000	0
Research and development expenses, net	1,642,000	0
Less valuation allowance	(23,167,000)	(17,703,000)
Deferred tax asset, net of valuation	4,000	83,000
Deferred tax liabilities:
Property and equipment	(4,000)	(8,000)
Stock-based compensation	0	(75,000)
Deferred tax liabilities	(4,000)	(83,000)
Net tax assets	$ 0	$ 0