Accrued Expense (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued Expense
Accrued expense	$ 1,058	$ 770
Accrued vacation and bonus expenses	500	400
Manufacturing and testing services	300
Professional and consulting fees	100
Accrued legal and patent fees	100	100
Other accrued expenses	$ 100	100
Manufacturing expenses		$ 100