Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Total revenue	$ 10,120	$ 9,178	$ 32,054	$ 27,850
Cost of sales	7,791	4,824	19,183	14,692
Gross profit	2,329	4,354	12,871	13,158
Operating expenses:
Research and development	2,579	3,395	8,383	10,912
General and administrative	2,549	3,050	7,797	9,501
Sales and marketing	912	1,491	3,071	4,094
Total operating expenses	6,040	7,936	19,251	24,507
Loss from operations	(3,711)	(3,582)	(6,380)	(11,349)
Interest expense	(157)	(170)	(501)	(567)
Other (expense) income, net	(27)	89	(40)	327
Net loss and comprehensive loss	$ (3,895)	$ (3,663)	$ (6,921)	$ (11,589)
Net loss per common share, basic and diluted	$ (0.21)	$ (0.21)	$ (0.37)	$ (0.67)
Weighted-average shares used to compute net loss per common share, basic and diluted	18,942,163	17,312,226	18,705,149	17,183,306
Product sales
Total revenue	$ 9,577	$ 8,370	$ 30,139	$ 25,396
Licensing, royalty and other revenue
Total revenue	$ 543	$ 808	$ 1,915	$ 2,454