Condensed Statements of Cash Flows - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities
Net loss		$ (11,343)	$ (23,168)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and accretion		49	78
Stock-based compensation		943	1,261
Change in fair value of warrant liabilities		1,796	(1,585)
Loss on issuance of warrants			2,033
Other		150	237
Changes in assets and liabilities:
Accounts receivable		249	2,119
Inventories		(258)	(150)
Prepaid expenses and other assets		693	796
Accounts payable		(1,383)	(2,126)
Accrued liabilities		(1,328)	1,721
Deferred revenue			178
Total adjustments		911	4,562
Net cash used in operating activities		(10,432)	(18,606)
Cash flows from investing activities
Purchases of property and equipment			(39)
Purchases of available-for-sale securities		(887)	(3,044)
Proceeds from maturities of short-term investments		2,200
Net cash provided by (used in) investing activities		1,313	(3,083)
Cash flows from financing activities
Payments on equipment financing obligations			(1)
Payments on term loan principal		(4,286)	(714)
Net proceeds from issuances of common stock pursuant to the 2021 Sales Agreement		648	658
Net proceeds from issuance of common stock upon exercise of stock options and from the ESPP		3	23
Proceeds from issuances of warrants and common stock			10,000
Net cash (used in) provided by financing activities		(3,635)	9,966
Net decrease in cash, cash equivalents, and restricted cash		(12,754)	(11,723)
Cash, cash equivalents, and restricted cash, beginning of the period	[1]	28,550	43,633
Cash, cash equivalents, and restricted cash, end of the period	[1]	$ 15,796	$ 31,910

[1] Includes restricted cash of $150,000 included in long-term restricted investments on the condensed balance sheets at June 30, 2024 and December 31, 2023 and short-term restricted investments on the condensed balance sheets June 30, 2023, respectively.