Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities
Net loss	$ (4,507)	$ (5,347)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	140	160
Non-cash lease expense	3	7
Stock-based compensation	2,589	2,655
Accretion and short-term investment discount		(197)
Changes in operating assets and liabilities:
Accounts receivable	(131)	216
Inventories	174	(97)
Prepaid expenses and other current assets	(169)	(7)
Other assets	21	24
Accounts payable	117	563
Accrued liabilities	192	(1,547)
Deferred revenue	(775)	768
Net cash used in operating activities	(2,346)	(2,802)
Cash flows from investing activities
Purchase of property and equipment		(349)
Net cash used in investing activities		(349)
Cash flows from financing activities
Proceeds from issuance of stock, net of issuance costs	30	56
Net cash provided by financing activities	30	56
Net decrease in cash, cash equivalents, and restricted cash	(2,316)	(3,095)
Cash, cash equivalents, and restricted cash at beginning of period	20,562	9,855
Cash, cash equivalents, and restricted cash at end of period	18,246	6,760
Supplemental disclosure of cash flow information:
Purchase of property and equipment included in accounts payable		15
Reconciliation of cash, cash equivalents, and restricted cash to balance sheet as of March 31st:
Cash and cash equivalents	17,633	5,623
Restricted cash - current	525	525
Restricted cash	88	612
Total cash, cash equivalents, and restricted cash	$ 18,246	$ 6,760