Balance Sheets - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 4,043,681	$ 3,949,135
Accounts receivable, net of allowances of $25,000 at December 31, 2017 and 2016	1,049,329	738,729
Inventories	1,369,647	1,252,238
Prepaid expenses and other current assets	2,640,717	1,646,821
Total current assets	9,103,374	7,586,923
Fixed assets, net	440,842	532,706
Other long-term assets	55,008	164,262
Total assets	9,599,224	8,283,891
Current liabilities:
Accounts payable	733,305	734,048
Accrued compensation	786,184	307,471
Accrued expenses	2,242,315	1,648,731
Deferred revenue	820,031	628,236
Total current liabilities	4,581,835	3,318,486
Common stock warrants	0	4,641
Total liabilities	4,581,835	3,323,127
Commitments and contingencies (Note 8)
Stockholders’ equity
Common stock, $0.0001 par value; 100,000,000 authorized at December 31, 2017 and 2016; 2,706,066 and 836,863 shares issued and outstanding at December 31, 2017 and 2016, respectively	271	84
Additional paid-in capital	196,355,142	183,439,463
Accumulated deficit	(191,338,054)	(178,478,801)
Total stockholders’ equity	5,017,389	4,960,764
Total liabilities and stockholders’ equity	9,599,224	8,283,891
Preferred stock
Stockholders’ equity
Preferred stock	0	0
Convertible preferred stock
Stockholders’ equity
Preferred stock	$ 30	$ 18