Note 10 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax assets:
Allowance for doubtful accounts	$ 5,060	$ 773
Inventory capitalization	6,197	6,813
Depreciation and amortization		70,272
Research & development tax credits	413,680	496,930
Compensation costs	1,035,983	838,643
Vacation accrual	167,644	179,309
Interest expense carryforward	66,149
Net operating loss carryforward	832,565
Capital loss carryforward	16,446	16,446
Total deferred tax asset	2,543,724	1,609,186
Deferred incomes tax liability:
Property and equipment - tax over book depreciation	(439,310)
Less valuation allowance
Deferred income taxes	$ 2,104,414	$ 1,609,186