Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net loss	$ (2,502)	$ (5,934)
Adjustments to reconcile net loss to net cash used in operating activities:
(Gain) from change in fair value of derivative warrant liability	(477)	(3,226)
(Gain) from change in fair value of 2020 Notes embedded derivative	(2,858)
Loss from the change in fair value of the 2017 Notes		339
Loss on exchange of debt	21	964
(Gain) on extinguishment of warrant liability		(33)
Stock-based compensation	98	128
Depreciation and amortization	1,646	1,676
Non-cash interest expense	402	80
Changes in operating assets and liabilities:
Accounts receivable	(234)	(82)
Inventories	7	(720)
Prepaid expenses and other current assets	78	(11)
Accounts payable, accrued expenses, and long-term liabilities	(531)	(1,228)
Net cash used in operating activities	(4,350)	(8,047)
Investing Activities
Acquisitions of property, plant and equipment	(67)	(673)
Net cash used in investing activities	(67)	(673)
Financing Activities
Payments on secured debt		(9,616)
Debt and equity offering costs	(164)	(205)
Proceeds from issuance of common stock and common stock warrants	57	11,044
Proceeds from the exercise of warrants		2
Net cash (used in)/provided by financing activities	(107)	1,225
Net (decrease) in cash and cash equivalents	(4,524)	(7,495)
Beginning of period	11,553	30,499
End of period	7,029	23,004
Cash paid for interest, net of interest capitalized	434	1,616
Non-cash purchase of property, plant and equipment	1	461
Exchange of convertible debt into common stock	515	8,177
Accrued offering costs		73
Fair value of warrants at issuance and upon exercise, net		$ 5,503