Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($)	Total	LP Purchase Agreement	ATM Offering	Private Placement	Series A Convertible Preferred Stock	Series A Convertible Preferred Stock Private Placement	Common Stock	Common Stock LP Purchase Agreement	Common Stock ATM Offering	Additional Paid-In Capital	Additional Paid-In Capital LP Purchase Agreement	Additional Paid-In Capital ATM Offering	Additional Paid-In Capital Private Placement	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2018	$ 21,092,062						$ 28,585			$ 172,086,909				$ (3,453)	$ (151,019,979)
Balance, shares at Dec. 31, 2018							28,585,449
Exercise of stock options	51,570						$ 22			51,548
Exercise of stock options, shares							21,871
Stock-based compensation expense	241,233									241,233
Release of restricted stock awards	13						$ 13
Release of restricted stock awards, shares							13,126
Net share settlement of restricted stock award	(9,685)						$ (4)			(9,681)
Net share settlement of restricted stock award, shares							(3,813)
Employee stock purchase plan expense	16,794									16,794
Net loss	(5,370,846)														(5,370,846)
Unrealized gain (loss) on short-term investments	3,353													3,353
Foreign currency translation adjustment	6,439													6,439
Balance at Mar. 31, 2019	16,030,933						$ 28,616			172,386,803				6,339	(156,390,825)
Balance, shares at Mar. 31, 2019							28,616,633
Balance at Dec. 31, 2018	21,092,062						$ 28,585			172,086,909				(3,453)	(151,019,979)
Balance, shares at Dec. 31, 2018							28,585,449
Net loss	(10,168,116)
Unrealized gain (loss) on short-term investments	4,172
Balance at Jun. 30, 2019	11,669,992						$ 28,707			172,831,416				(2,036)	(161,188,095)
Balance, shares at Jun. 30, 2019							28,707,047
Balance at Mar. 31, 2019	16,030,933						$ 28,616			172,386,803				6,339	(156,390,825)
Balance, shares at Mar. 31, 2019							28,616,633
Exercise of stock options	69,384						$ 32			69,352
Exercise of stock options, shares							32,385
Stock-based compensation expense	287,317									287,317
Release of restricted stock awards	15						$ 15
Release of restricted stock awards, shares							15,001
Net share settlement of restricted stock award	(11,152)						$ (4)			(11,148)
Net share settlement of restricted stock award, shares							(4,461)
Stock issued under stock purchase plans	99,140						$ 48			99,092
Stock issued under stock purchase plans, shares							47,489
Net loss	(4,797,270)														(4,797,270)
Unrealized gain (loss) on short-term investments	819													819
Foreign currency translation adjustment	(9,194)													(9,194)
Balance at Jun. 30, 2019	11,669,992						$ 28,707			172,831,416				(2,036)	(161,188,095)
Balance, shares at Jun. 30, 2019							28,707,047
Balance at Dec. 31, 2019	23,969,634						$ 58,090			194,234,151				(4,964)	(170,317,643)
Balance, shares at Dec. 31, 2019							58,090,233
Stock-based compensation expense	415,256									415,256
Release of restricted stock awards	36						$ 36
Release of restricted stock awards, shares							35,942
Net share settlement of restricted stock award	(7,052)						$ (11)			(7,041)
Net share settlement of restricted stock award, shares							(11,266)
Employee stock purchase plan expense	5,379									5,379
Issuance of common stock			$ 2,435,912					$ 615	$ 4,399		$ (615)	$ 2,431,513
Issuance of common stock, shares								615,384	4,399,062
Issuance of preferred stock	2,424,900			$ 562,955	$ 41	$ 10				2,424,859			$ 562,945
Issuance of preferred stock, shares					41,100	10,170
Cancellation of common stock received in exchange for Series A convertible preferred stock	(2,424,900)						$ (4,110)			(2,420,790)
Cancellation of common stock received in exchange for Series A convertible preferred stock, shares							(4,110,000)
Exercise of pre-funded warrants	31,768						$ 3,177			28,591
Exercise of pre-funded warrants, shares							3,176,762
Adjustment in connection with LP Purchase Agreement commitment fee and transaction costs		$ (96,000)									(96,000)
Net loss	(5,457,898)														(5,457,898)
Unrealized gain (loss) on short-term investments	47,697													47,697
Foreign currency translation adjustment	5,497													5,497
Balance at Mar. 31, 2020	21,913,184				$ 51		$ 62,196			197,578,248				48,230	(175,775,541)
Balance, shares at Mar. 31, 2020					51,270		62,196,117
Balance at Dec. 31, 2019	23,969,634						$ 58,090			194,234,151				(4,964)	(170,317,643)
Balance, shares at Dec. 31, 2019							58,090,233
Issuance of common stock, shares									6,483,776
Net loss	(11,168,449)
Unrealized gain (loss) on short-term investments	21,561
Balance at Jun. 30, 2020	18,683,907				$ 24		$ 67,093			200,079,879				23,003	(181,486,092)
Balance, shares at Jun. 30, 2020					23,770		67,093,683
Balance at Mar. 31, 2020	21,913,184				$ 51		$ 62,196			197,578,248				48,230	(175,775,541)
Balance, shares at Mar. 31, 2020					51,270		62,196,117
Stock-based compensation expense	361,477									361,477
Release of restricted stock awards	24						$ 24
Release of restricted stock awards, shares							23,751
Net share settlement of restricted stock award	(2,108)						$ (7)			(2,101)
Net share settlement of restricted stock award, shares							(6,389)
Stock issued under stock purchase plans	30,512						$ 45			30,467
Stock issued under stock purchase plans, shares							45,490
Issuance of common stock			$ 1,395,058						$ 2,085			$ 1,392,973
Issuance of common stock, shares									2,084,714
Conversion of Series A convertible preferred stock for common stock					$ (27)		$ 2,750			(2,723)
Conversion of Series A convertible preferred stock for common stock, shares					(27,500)		2,750,000
Adjustment in connection with LP Purchase Agreement commitment fee and transaction costs		$ 301,538									$ 301,538
Issuance of common stock warrants in connection with SVB Term Loan	420,000									420,000
Net loss	(5,710,551)														(5,710,551)
Unrealized gain (loss) on short-term investments	(26,136)													(26,136)
Foreign currency translation adjustment	909													909
Balance at Jun. 30, 2020	$ 18,683,907				$ 24		$ 67,093			$ 200,079,879				$ 23,003	$ (181,486,092)
Balance, shares at Jun. 30, 2020					23,770		67,093,683