CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 60,393	$ 71,655
Accounts receivable, net	11,948	8,243
Inventories	9,103	9,137
Prepaid expenses and other current assets	4,021	4,066
Total current assets	85,465	93,101
Property and equipment, net	15,696	15,086
Restricted cash	1,852	1,852
Goodwill	549	588
Intangible assets, net	303	353
Deferred income tax assets	63	66
Other long-term assets	856	844
Total assets	104,784	111,890
Current liabilities
Accounts payable	4,614	3,375
Contract liabilities	175	137
Accrued expenses and other current liabilities	12,152	9,187
Short-term line of credit	4,489	3,491
Total current liabilities	21,430	16,190
Long-term loans payable, net	41,858	41,787
Other long-term liabilities	127	174
Total liabilities	63,415	58,151
Commitments and contingencies (Note 9)
Stockholders' equity
Preferred stock ($0.001 par value) 25,000,000 shares authorized; no shares issued and outstanding as of March 31, 2020 and December 31, 2019
Common stock ($0.001 par value) 175,000,000 shares authorized as of March 31, 2020 and December 31, 2019, 20,917,149 and 20,851,531 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively	21	21
Additional paid-in capital	320,660	319,115
Accumulated other comprehensive income (loss)	(27)	44
Accumulated deficit	(279,285)	(265,441)
Total stockholders' equity	41,369	53,739
Total liabilities and stockholders’ equity	$ 104,784	$ 111,890