Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Research and development expenses (Details)

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Research and development expenses (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Research and development expenses      
Labor $ 5,471,136 $ 4,403,038 $ 2,763,805
Materials 2,383,730 3,253,593 2,618,226
Government grants   (476,985) (1,087,344)
Research and development expenses $ 7,854,866 $ 7,179,646 $ 4,294,687