CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
REVENUE:
Total revenue	$ 571	$ 706	$ 1,207	$ 1,788
Cost of revenue	1,911	1,427	4,172	2,909
Gross loss	(1,340)	(721)	(2,965)	(1,121)
OPERATING EXPENSES:
Research and development	5,897	10,762	15,339	19,338
Sales and marketing	2,604	5,323	8,872	9,939
General and administrative	6,345	9,827	14,899	21,157
Total operating expenses	14,846	25,912	39,110	50,434
LOSS FROM OPERATIONS	(16,186)	(26,633)	(42,075)	(51,555)
OTHER INCOME (EXPENSE):
Change in fair value of convertible note and warrant liabilities	(116)	141	(926)	109
Interest income and other	301	350	578	774
Interest expense and other	(11)	(307)	165	(650)
Total other income (expense), net	174	184	(183)	233
Provision for income tax expense	19	18	38	26
Net loss	$ (16,031)	$ (26,467)	$ (42,296)	$ (51,348)
PER SHARE DATA
Net loss per common share (basic) (in dollars per share)	$ (0.09)	$ (0.17)	$ (0.25)	$ (0.33)
Net loss per common share (diluted) (in dollars per share)	$ (0.09)	$ (0.17)	$ (0.25)	$ (0.33)
Weighted average common shares outstanding (basic) (in shares)	175,675,994	157,310,419	168,962,722	156,071,676
Weighted average common shares outstanding (diluted) (in shares)	175,675,994	157,310,419	168,962,722	156,071,676
COMPREHENSIVE LOSS:
Net loss	$ (16,031)	$ (26,467)	$ (42,296)	$ (51,348)
Change in net unrealized loss on available-for-sale securities, net of tax	420	(182)	910	(1,238)
Change in fair value due to instrument-specific credit risk, net of tax	0	0	(21)	0
Comprehensive loss	(15,611)	(26,649)	(41,407)	(52,586)
Prototype sales
REVENUE:
Total revenue	245	195	370	530
Development contracts
REVENUE:
Total revenue	$ 326	$ 511	$ 837	$ 1,258