Note 5 - Share-based Compensation - Stock Compensation Expense (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stock compensation expense	$ 374,380	$ 313,873	$ 747,805	$ 643,768
Research and Development Expense [Member]
Stock compensation expense	64,752	58,815	130,346	118,080
Selling and Marketing Expense [Member]
Stock compensation expense	69,242	58,051	137,755	117,670
General and Administrative Expense [Member]
Stock compensation expense	191,003	154,983	381,953	323,181
Cost of Sales [Member]
Stock compensation expense	$ 49,383	$ 42,024	$ 97,751	$ 84,837

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
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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