Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Total revenue	$ 11,826	$ 8,646	$ 21,934	$ 18,672
Cost of sales	6,635	4,627	11,392	9,868
Gross profit	5,191	4,019	10,542	8,804
Operating expenses:
Research and development	2,774	3,519	5,804	7,517
General and administrative	2,448	2,856	5,248	6,451
Sales and marketing	1,056	1,239	2,159	2,603
Total operating expenses	6,278	7,614	13,211	16,571
Loss from operations	(1,087)	(3,595)	(2,669)	(7,767)
Interest expense	(172)	(186)	(344)	(397)
Other (expense) income, net	(35)	111	(13)	238
Net loss and comprehensive loss	$ (1,294)	$ (3,670)	$ (3,026)	$ (7,926)
Net loss per common share, basic and diluted	$ (0.07)	$ (0.21)	$ (0.16)	$ (0.46)
Weighted-average shares used to compute net loss per common share, basic and diluted	18,747,124	17,137,338	18,585,339	17,117,777
Product sales
Total revenue	$ 10,927	$ 8,003	$ 20,562	$ 17,026
Licensing, royalty and other revenue
Total revenue	$ 899	$ 643	$ 1,372	$ 1,646