Note 10 - Stockholders' Equity - Stock-based Compensation (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Stock-based compensation	$ 258,000	$ 67,000
Cost of Sales [Member]
Stock-based compensation	5,000
Selling, General and Administrative Expenses [Member]
Stock-based compensation	216,000	52,000
Research and Development Expense [Member]
Stock-based compensation	$ 37,000	$ 15,000

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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