Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (35,970)	$ (28,414)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	900	1,000
Stock-based compensation	7,954	5,824
Patent write-offs	641	383
Other	1	6
Operating lease right-of-use asset amortization	632	602
Finance lease right-of-use asset amortization	41	0
Changes in assets and liabilities:
Accounts receivable	160	(130)
Prepaids and other current assets	(125)	(134)
Other assets	59	(44)
Accounts payable	298	(245)
Accrued expenses	(106)	19
Accrued salaries and payroll related expenses	1,085	(55)
Operating lease liabilities	(685)	(501)
Deferred revenue	5,013	52
Net cash used in operating activities	(20,102)	(21,637)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(707)	(705)
Expenditures for patents	(1,254)	(881)
Net cash used in investing activities	(1,961)	(1,586)
CASH FLOWS FROM FINANCING ACTIVITIES
Gross proceeds from the sale of common stock	18,614	40,173
Offering costs in connection with the sale of common stock	(628)	(2,726)
Principal payments on finance lease	(30)	0
Proceeds from exercises of stock options	293	10
Net cash provided by financing activities	18,249	37,457
Effects of currency translation on cash, cash equivalents and restricted cash	2	1
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(3,812)	14,235
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — Beginning of year	25,073	10,838
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — End of year	21,261	25,073
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for taxes	1	2
Cash paid for interest	7	0
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Common stock issued in settlement of accrued salaries and payroll related expenses	442	343
Property and equipment included in accounts payable	67	193
Property and equipment included in accrued expenses	33	68
Patents included in accounts payable	210	224
Finance lease liability included in accounts payable	4	0
Property acquired through finance lease obligation	0	204
Operating lease assets obtained in exchange for new lease liabilities	0	114
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents
Cash and cash equivalents	21,206	24,968
Restricted cash	55	105
Total cash, cash equivalents and restricted cash	$ 21,261	$ 25,073