Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues	$ 1,240	$ 2,014	$ 3,091	$ 4,202
Operating expenses:
Total cost of revenue	1,823	1,681	3,066	3,554
Gross profit	(583)	333	25	648
Research and development expense	5,945	6,691	11,918	11,519
Sales, marketing, general and administrative expense	2,455	2,093	5,154	4,700
Total operating expenses	8,400	8,784	17,072	16,219
Loss from operations	(8,983)	(8,451)	(17,047)	(15,571)
Other expense, net	(7)	(8)	(11)	(20)
Net loss	$ (8,990)	$ (8,459)	$ (17,058)	$ (15,591)
Net loss per share - basic and diluted	$ (0.08)	$ (0.10)	$ (0.16)	$ (0.19)
Weighted-average shares outstanding - basic and diluted	106,872	81,321	104,435	79,973
Product revenue
Revenue from Contract with Customer, Including Assessed Tax	$ 0	$ 0	$ 199	$ 0
Operating expenses:
Cost of Goods and Services Sold	1,025	326	1,313	564
License and royalty
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	11
Contract
Revenue from Contract with Customer, Including Assessed Tax	1,240	2,014	2,892	4,191
Operating expenses:
Cost of Goods and Services Sold	$ 798	$ 1,355	$ 1,753	$ 2,990