Note 5 - Share-based Compensation - Stock Compensation Expense (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock compensation expense	$ 383,140	$ 313,943	$ 1,130,945	$ 957,711
Research and Development Expense [Member]
Stock compensation expense	64,970	59,434	195,316	177,514
Selling and Marketing Expense [Member]
Stock compensation expense	64,152	55,402	201,907	173,072
General and Administrative Expense [Member]
Stock compensation expense	194,764	156,621	576,718	479,803
Cost of Sales [Member]
Stock compensation expense	$ 59,254	$ 42,486	$ 157,004	$ 127,322

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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