Condensed Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (5,370,846)	$ (5,379,947)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	308,984	356,204
Accretion of discount on NuvoGen obligation	(3,414)	(2,952)
Provision for excess inventory	24,296	11,280
Amortization of Growth Term Loan discount and issuance costs		62,951
Loss on extinguishment of Growth Term Loan		105,064
Amortization of QNAH Convertible Note issuance costs	3,364	3,363
Amortization of MidCap Credit Facility discount and issuance costs	39,143	2,924
Stock-based compensation expense	241,246	1,143,458
Employee stock purchase plan expense	16,794	14,453
Amortization of operating lease right-of-use assets	72,923
Amortization of incentive from landlord		(35,500)
Accrued interest on available-for-sale securities investments	(72,698)	(66,195)
Changes in operating assets and liabilities:
Accounts receivable	1,662,828	3,351,907
Inventory	103,272	127,224
Prepaid expenses and other	9,777	(21,494)
Deferred offering costs		2,953
Accounts payable	(480,546)	(78,239)
Accrued liabilities	(1,977,373)	(2,065,603)
Contract liabilities	(55,246)	(233,078)
Operating lease liabilities	(115,440)
Net cash used in operating activities	(5,592,936)	(2,701,227)
Investing activities
Purchase of property and equipment	(103,316)	(457,828)
Sales, redemptions and maturities of available-for-sale securities	12,800,000
Purchase of available-for-sale securities	(8,099,573)	(25,070,165)
Net cash provided by (used in) investing activities	4,597,111	(25,527,993)
Financing activities
Proceeds from MidCap Credit Facility		7,000,000
MidCap Credit Facility lender fees		(228,459)
Payments on Growth Term Loan		(1,684,626)
Payments for extinguishment of Growth Term Loan		(4,276,988)
Proceeds from public offering, net of underwriting discounts, commissions and costs of $2.6 million		37,724,316
Proceeds from ATM Offering, net		556,706
Payments on NuvoGen obligation	(463,686)	(185,574)
Payments on financing leases	(13,782)	(20,786)
Proceeds from exercise of stock options	51,570	40,504
Taxes paid for net share settlement of restricted stock awards	(9,685)	(133,513)
Payment of deferred offering costs	(30,175)
Net cash (used in) provided by financing activities	(465,758)	38,791,580
Effect of exchange rates on cash	4,063
(Decrease) increase in cash, cash equivalents and restricted cash	(1,457,520)	10,562,360
Cash, cash equivalents and restricted cash at beginning of year	11,702,847	9,968,600
Cash, cash equivalents and restricted cash at end of period	10,245,327	20,530,960
Supplemental disclosure of noncash investing and financing activities
Fixed asset purchases payable and accrued at period end	13,945	3,486
Adoption of ASC 842, Leases	694,352
Deferred offering costs payable and accrued at period end	108,883
Equipment purchased through capital leases		31,340
Debt issuance costs payable and accrued at period end		193,931
MidCap Term Loan fees and warrant discount		389,000
Supplemental cash flow information
Cash paid for interest	$ 172,032	$ 83,397