Balance Sheet Details - Schedule of Fixed Assets and Accrued Liabilities (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Fixed Assets
Machinery and equipment	$ 2,810,226	$ 2,841,388
Furniture and office equipment	157,391	147,976
Computer equipment and software	1,430,669	1,637,034
Leasehold improvements	570,174	553,529
Financed equipment	2,526,081	2,294,762
Construction in process	128,377	2,975
Total fixed assets, gross	7,622,918	7,477,664
Less accumulated depreciation and amortization	(4,721,924)	(4,354,097)
Total fixed assets, net	2,900,994	3,123,567
Accrued Liabilities
Accrued payroll	387,162	224,813
Accrued vacation	470,473	474,953
Accrued bonuses	804,281	375,000
Accrued sales commissions	42,168	104,509
Current portion of deferred rent	147,771	116,681
Accrued other	102,115	129,805
Total accrued liabilities	$ 1,953,970	$ 1,425,761