Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating activities:
Net loss	$ (12,623)	$ (15,004)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	60	68
Non-cash interest expense on convertible stockholder notes	0	3
Gain on extinguishment of Paycheck Protection Program note payable	0	(509)
Share-based compensation	1,661	2,952
Loss on disposal of property and equipment	19	0
Changes in operating assets and liabilities:
Accounts receivable	85	(85)
Inventory	0	4
Prepaid expenses and other current assets	(179)	241
Other receivable due from related party	618	(618)
Accounts payable	(239)	(168)
Accrued liabilities and other current liabilities	130	797
Deferred revenue	164	(8)
Operating lease liability - current	(618)	86
Operating lease liability - noncurrent	(24)	(614)
Right-of-use assets	580	498
Net cash used in operating activities	(10,366)	(12,357)
Investing activities:
Purchase of property and equipment	(116)	(32)
Net cash used in investing activities	(116)	(32)
Financing activities:
Proceeds from sale of common stock	2,001	0
Issuance costs of sale of common stock	(59)	(2,635)
Proceeds from Paycheck Protection Program note payable	0	506
Tax withholding payments on settlement of restricted stock unit awards	0	(160)
Proceeds from exercise of common stock options	5	0
Net cash provided by financing activities	1,947	28,211
Net change in cash and cash equivalents	(8,535)	15,822
Cash and cash equivalents at beginning of year	21,407	5,585
Cash and cash equivalents at end of year	12,872	21,407
Supplemental disclosure for noncash investing and financing activities:
Restricted stock units issued to settle management bonus obligations	393	391
Restricted stock units issued to settle board compensation obligations	0	613
Common stock grants to former directors to settle board compensation obligations	0	148
Right-of-use asset obtained in exchange for lease obligation	1,896	0
Public Offering [Member]
Financing activities:
Proceeds from sale of common stock	0	11,500
The $8.5 Million Registered Direct Offering [Member]
Financing activities:
Proceeds from sale of common stock	0	8,500
The $10.5 Million Registered Direct Offering [Member]
Financing activities:
Proceeds from sale of common stock	$ 0	$ 10,500