Note 10 - Equity Incentive Plans (Details Textual) - USD ($)	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 28, 2024	Jun. 11, 2024	May 31, 2024	Feb. 27, 2024	Dec. 31, 2023	Nov. 30, 2023	May 31, 2023	Aug. 04, 2022	Jun. 16, 2021	Jun. 08, 2020	Apr. 23, 2019
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	45,688,228						27,043,664
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number (in shares)	21,699,803						17,938,726
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 2.5						$ 2.9
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year)	7 years 1 month 2 days
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value	$ 35,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number (in shares)	12,175,103
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 2.98
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term (Year)	5 years 6 months 18 days
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$ 35,000
Proceeds from Stock Options Exercised	$ 21,000	$ 17,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period (in shares)	26,980	54,720
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 6,000	$ 31,000
Share Price (in dollars per share)			$ 0.67
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 1.01	$ 0.78
Proceeds from Stock Plans	$ 312,000	$ 298,000
Options and RSU [Member]
Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount	$ 18,700,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	2 years 4 months 24 days
The 2019 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)				43,900,000						28,900,000	16,900,000	8,000,000	1,600,000
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	16,621,469						5,685,806
The 2024 Inducement Award Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	1,727,500					3,000,000	0
The 2022 ESPP [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	2,362,902			3,600,000						1,800,000
Share Price (in dollars per share)					$ 0.27			$ 0.54	$ 0.46
Proceeds from Stock Plans	$ 300,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)	502,423
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 0