Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenues:
Product sales	$ 969	$ 1,852	$ 2,431	$ 3,278
Other revenue	196	82	333	198
Total revenues	1,165	1,934	2,764	3,476
Cost of revenues:
Products and services	708	1,247	1,640	2,184
Restructuring inventory charge	0	747	0	747
Total cost of revenues	708	1,994	1,640	2,931
Gross profit (loss)	457	(60)	1,124	545
Operating expenses:
Selling, general and administrative	3,764	6,579	8,370	11,557
Research and development	1,476	1,162	2,971	2,227
Total operating expenses	5,240	7,741	11,341	13,784
Loss from operations	(4,783)	(7,801)	(10,217)	(13,239)
Other income (expense):
Interest income	0	8	2	10
Other	(2)	(6)	(2)	1
Nonoperating Income (Expense), Total	(2)	2	0	11
Net loss	$ (4,785)	$ (7,799)	$ (10,217)	$ (13,228)
Net loss per basic and diluted common share (in dollars per share)	$ (0.12)	$ (0.20)	$ (0.25)	$ (0.35)
Weighted average common shares used to compute net loss per basic and diluted common share (in shares)	40,978,820	38,162,526	40,943,241	37,938,873
Comprehensive loss:
Net loss	$ (4,785)	$ (7,799)	$ (10,217)	$ (13,228)
Net unrealized gain (loss) on short-term investments	12	(4)	(11)	(2)
Comprehensive loss	$ (4,773)	$ (7,803)	$ (10,228)	$ (13,230)