Note 13 - Revenues (Details Textual)		12 Months Ended
	Aug. 30, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Contract with Customer, Liability, Total		$ 608,000	$ 620,000
Contract with Customer, Liability, Current		719,000	608,000
Contract with Customer, Liability, Noncurrent		1,244,000	1,596,000
Exclusivity Fee [Member]
Contract with Customer, Liability, Total	$ 2,000,000
Contract with Customer, Liability, Current		286,000	$ 286,000
Supply Agreement [Member]
Supply Agreement, Term (Year)	5 years
Supply Agreement, Renewal Term, Number of Options	2
Supply Agreement, Renewal Term, Per Option (Year)	2 years
Distribution Agreement with AXP Distributor in China [Member]
Lessor, Sales-type Lease, Assumptions and Judgments, Value of Underlying Asset, Amount		$ 170,000
Property, Plant and Equipment, Useful Life (Year)		5 years
Proceeds from Customers		$ 41,000
Minimum [Member]
Period Of Warranty On Products (Year)		1 year
Maximum [Member]
Period Of Warranty On Products (Year)		2 years
Maximum [Member] | Supply Agreement [Member]
Supply Agreement, Renewal Term (Year)	4 years