Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (18,960,017)	$ (26,039,550)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,241,873	1,473,778
Accretion of discount on NuvoGen obligation	195,248	206,985
Provision for excess inventory	366,963	723,466
Amortization of Growth Term Loan discount and issuance costs	404,462	551,121
Amortization of QNAH Convertible Note issuance costs	1,269
Stock-based compensation expense	1,376,969	903,584
Employee stock purchase plan expense	59,118	98,544
Accretion of incentive from landlord	(142,000)	(130,167)
Accrued interest on available-for-sale securities investments		172,045
Loss on disposal of assets	81,539	98,685
Changes in operating assets and liabilities:
Accounts receivable	(4,978,827)	(661,195)
Inventory	77,176	(33,218)
Prepaid expenses and other	(3,749)	11,889
Deferred offering costs	49,630
Accounts payable	1,225,954	10,073
Accrued liabilities	2,076,500	119,928
Deferred revenue	355,584	259,824
Net cash used in operating activities	(16,572,308)	(22,234,208)
Investing activities
Purchase of property and equipment	(1,020,531)	(1,946,515)
Sales, redemptions and maturities of available-for-sale securities	4,300,000	29,750,000
Purchase of available-for-sale securities		(3,381,271)
Net cash provided by investing activities	3,279,469	24,422,214
Financing activities
Proceeds from issuance of convertible note to QNAH, a related party	3,000,000
QNAH Convertible Note financing costs	(40,509)
Proceeds from Growth Term Loan		5,000,000
Payments on Growth Term Loan	(6,389,782)	(4,446,396)
Proceeds from ATM Offering, net	19,908,954
ATM Offering costs	(231,476)
Proceeds from private investor		2,000,000
Payments on NuvoGen obligation	(800,000)	(543,750)
Payments on capital leases	(69,142)	(133,079)
Proceeds from exercise of stock options	112,138	23,851
Proceeds from shares purchased under the stock purchase plan	266,549	174,674
Payment of deferred offering costs	(2,952)	(49,630)
Net cash provided by financing activities	15,753,780	2,025,670
Increase in cash and cash equivalents	2,460,941	4,213,676
Cash and cash equivalents at beginning of year	7,507,659	3,293,983
Cash and cash equivalents at end of year	9,968,600	7,507,659
Noncash investing and financing activities
Fixed asset purchases payable and accrued at year end	477,966	26,785
Carrying value of demonstration units transferred from property and equipment to inventory	113,607
Stock issued for settlement of accrued bonus		(364,910)
Purchase of property and equipment under capital lease		227,147
Incentive from landlord		710,000
Retirement of treasury stock	75,000
Supplemental cash flow information
Cash paid for interest	698,065	1,109,359
Cash paid for taxes	$ 1,967	$ 7,090