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Note 2 - Summary of Significant Accounting Policies (Details Textual)
3 Months Ended 12 Months Ended
Mar. 20, 2020
USD ($)
Mar. 31, 2023
USD ($)
Mar. 31, 2022
USD ($)
Dec. 31, 2022
USD ($)
Jan. 22, 2021
USD ($)
Accounts Receivable, Allowance for Credit Loss, Current   $ 12,000   $ 12,000  
Inventory Valuation Reserves   158,000   158,000  
Income (Loss) from Equity Method Investments   (6,000) $ (8,000)    
Contract with Customer, Liability   21,000      
Contract with Customer, Liability, Revenue Recognized   8,000      
Unrecognized Tax Benefits, Ending Balance   $ 0   0  
Operating Lease, Weighted Average Remaining Lease Term (Year)   9 years      
Operating Lease, Weighted Average Discount Rate, Percent   18.00%      
Operating Lease, Right-of-Use Asset   $ 837,000   $ 867,000  
Operating Lease, Liability   844,000      
Off-Balance-Sheet, Credit Loss, Liability   $ 0      
Minimum [Member]          
Property, Plant and Equipment, Useful Life (Year)   3 years      
Maximum [Member]          
Property, Plant and Equipment, Useful Life (Year)   5 years      
Canadian Government Grants [Member] | Minimum [Member]          
Grant Term (Month)   6 months      
Canadian Government Grants [Member] | Maximum [Member]          
Grant Term (Month)   18 months      
Odin Co Ltd [Member]          
Payments to Acquire Interest in Joint Venture $ 100,000        
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage 40.00% 40.00%   40.00%  
Income (Loss) from Equity Method Investments   $ 6,000 $ 8,000    
Odin Co Ltd [Member] | Tomorrow Water [Member]          
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage 30.00%        
Odin Co Ltd [Member] | BKT and Tomorrow Water [Member]          
Payments to Acquire Interest in Joint Venture $ 150,000        
Patents [Member]          
Intangible Assets, Net (Excluding Goodwill), Total         $ 34,000
Customer Concentration Risk [Member] | Revenue from Contract with Customer Benchmark [Member]          
Number of Major Customers     2    
Customer Concentration Risk [Member] | Revenue from Contract with Customer Benchmark [Member] | One Customer [Member]          
Number of Major Customers   1      
Concentration Risk, Percentage   10.00%      
Customer Concentration Risk [Member] | Revenue from Contract with Customer Benchmark [Member] | Two Customers [Member]          
Concentration Risk, Percentage     10.00%    
Customer Concentration Risk [Member] | Accounts Receivable [Member]          
Number of Major Customers   1      
Customer Concentration Risk [Member] | Accounts Receivable [Member] | One Customer [Member]          
Concentration Risk, Percentage   10.00%