Balance Sheet Details - Schedule of Fixed Assets and Accrued Liabilities (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Fixed Assets
Machinery and equipment	$ 2,841,388	$ 2,728,468
Furniture and office equipment	147,976	143,726
Computer equipment and software	1,637,034	620,582
Leasehold improvements	553,529	517,968
Financed equipment	2,294,762	1,559,690
Construction in process	2,975	169,896
Total fixed assets, gross	7,477,664	5,740,330
Less accumulated depreciation and amortization	(4,354,097)	(3,933,999)
Total fixed assets, net	3,123,567	1,806,331
Accrued Liabilities
Accrued interest	326,602	20,776
Accrued payroll	224,813	168,727
Accrued vacation	474,953	364,953
Accrued bonuses	375,000	422,868
Accrued sales commissions	104,509	77,844
Current portion of deferred rent	116,681	67,085
Accrued other	129,805	37,783
Total accrued liabilities	$ 1,752,363	$ 1,160,036