Income Taxes - Components of deferred tax assets (liabilities) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Components of deferred tax assets
Net operating loss carryforwards	$ 10,228,000	$ 5,530,000
Accruals and reserves	1,053,000	707,000
Research and development credits	1,368,000	640,000
Deferred Revenue	6,000
Depreciation and amortization	(23,000)	(4,000)
Deferred Tax Assets, Gross, Total	12,632,000	6,873,000
Valuation allowance change	(12,632,000)	(6,873,000)
Net change in the valuation allowance	$ 5,813,000	$ 2,386,000