REVENUE - Revenue by customer type and geographic area (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Product sales:
Total revenue	$ 8,707,310	$ 5,191,629
Product
Product sales:
Total revenue	8,155,969	4,576,579
Grant
Product sales:
Total revenue	551,341	615,050
United States | Product
Product sales:
Total revenue		66,800
United States | Grant
Product sales:
Total revenue	551,341	615,050
Germany | Product
Product sales:
Total revenue	4,913,588	3,098,176
All Other Countries | Product
Product sales:
Total revenue	3,242,381	1,411,603
Direct
Product sales:
Total revenue	6,409,394	3,981,205
Direct | Product
Product sales:
Total revenue	6,409,394	3,981,205
Direct | United States | Product
Product sales:
Total revenue	0	66,800
Direct | United States | Grant
Product sales:
Total revenue	0	0
Direct | Germany | Product
Product sales:
Total revenue	4,913,588	3,098,176
Direct | All Other Countries | Product
Product sales:
Total revenue	1,495,806	816,229
Distributors/Strategic Partners
Product sales:
Total revenue	1,746,575	595,374
Distributors/Strategic Partners | Product
Product sales:
Total revenue	1,746,575	595,374
Distributors/Strategic Partners | United States | Product
Product sales:
Total revenue	0	0
Distributors/Strategic Partners | United States | Grant
Product sales:
Total revenue	0	0
Distributors/Strategic Partners | Germany | Product
Product sales:
Total revenue	0	0
Distributors/Strategic Partners | All Other Countries | Product
Product sales:
Total revenue	1,746,575	595,374
United States Government Agencies
Product sales:
Total revenue	551,341	615,050
United States Government Agencies | Product
Product sales:
Total revenue	0	0
United States Government Agencies | United States | Product
Product sales:
Total revenue	0	0
United States Government Agencies | United States | Grant
Product sales:
Total revenue	551,341	615,050
United States Government Agencies | Germany | Product
Product sales:
Total revenue	0	0
United States Government Agencies | All Other Countries | Product
Product sales:
Total revenue	$ 0	$ 0