Stock compensation plan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	1,343,700	721,741
Options granted, weighted average fair value per share	$ 6.96	$ 0.47
Options granted, weighted average exercise price per share	$ 14.25	$ 0.53
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Weighted-average risk-free interest rate	1.00%	1.10%
Expected dividend yield	0.00%	0.00%
Expected volatility	51.00%	45.10%
Expected term	6 years 1 month 6 days	4 years 10 months 24 days
Stock-based compensation	$ 254	$ 312
Period for recognition	3 years 10 months 24 days	2 years 10 months 24 days
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Stock-based compensation	$ 16	$ 2
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Stock-based compensation	183	231
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Stock-based compensation	55	79
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted to employees	$ 9,322	327
Share-based Payment Arrangement, Grantee Status [Extensible List]	us-gaap:ShareBasedPaymentArrangementEmployeeMember
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Vesting period	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Unrecognized compensation	$ 9,051	$ 451