STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (11,908)	$ (12,286)
Adjustments to reconcile net loss to net cash used in operating activities:
Gain on investments	(47)	(36)
Amortization of discounts on investments		17
Depreciation and amortization	447	391
Stock-based compensation	3,413	3,728
Loss on sale of equipment	15
Loss on early extinguishment of debt	10
(Gain) loss on remeasurement of common stock warrant liability	1	(69)
(Increase) decrease in current assets:
Accounts receivable	(123)	(6)
Prepaid expenses	(172)	167
Inventory	(721)	(483)
Deposits	10	(10)
Increase (decrease) in current liabilities:
Accounts payable	(218)	40
Accrued contract cancellation settlement		(1,000)
Accrued expenses	189	218
Deferred rent	(25)	8
Net cash used in operating activities	(9,129)	(9,321)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of securities		(5,004)
Proceeds received on sale of securities	5,070
Proceeds received on sale of equipment	185
Purchase of property and equipment	(239)	(898)
Net cash provided by (used in) investing activities	5,016	(5,902)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from the issuance of common stock, net	5,132	5,253
Proceeds from the issuance of notes payable	9	437
Repayments of notes payable, net	(281)	(73)
Repayments of notes payable, related parties	(12)	(24)
Repayments of capital lease obligations	(71)	(95)
Proceeds from the exercise of warrants	2,213
Payment of employee withholding taxes relating to share-based awards	(58)
Net cash provided by financing activities	6,932	5,498
NET CHANGE IN CASH	2,819	(9,725)
CASH AT BEGINNING OF PERIOD	2,101	11,826
CASH AT END OF PERIOD	4,920	2,101
SUPPLEMENTAL INFORMATION:
Interest paid	74	87
Income taxes paid
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Deemed dividend	333
Purchases of equipment under capital lease obligations	$ 37	$ 316