Prepaid Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Director compensation	$ 156	$ 66
Director and officer insurance	102	33
NASDAQ fees	14
Legal retainer	25	25
Inventory purchase deposits	20	20
Professional services retainer	8	8
Equipment service deposits	5	7
Engineering, software licenses and other	6	11
Total prepaid expenses	$ 336	$ 170