Stockholders' equity (Details 1)	6 Months Ended
	Jun. 30, 2016 $ / shares shares
Outstanding	59,478,408
Warrant 1
Outstanding	625
Weighted Average Exercise Price | $ / shares	$ 9
Expiration Fiscal Period	3rd Qtr, 2016
Warrant 2
Outstanding	475,142
Weighted Average Exercise Price | $ / shares	$ 7.54
Expiration Fiscal Period	4th Qtr, 2016
Warrant 3
Outstanding	34,749
Weighted Average Exercise Price | $ / shares	$ 7.99
Expiration Fiscal Period	1st Qtr, 2017
Warrant 4
Outstanding	1,349,183
Weighted Average Exercise Price | $ / shares	$ 6.90
Expiration Fiscal Period	2nd Qtr, 2017
Warrant 5
Outstanding	536,500
Weighted Average Exercise Price | $ / shares	$ 1.14
Expiration Fiscal Period	3rd Qtr, 2017
Warrant 6
Outstanding	1,162,088
Weighted Average Exercise Price | $ / shares	$ 6.45
Expiration Fiscal Period	4th Qtr, 2017
Warrant 7
Outstanding	10,000
Weighted Average Exercise Price | $ / shares	$ 6.6
Expiration Fiscal Period	1st Qtr, 2018
Warrant 8
Outstanding	750,000
Weighted Average Exercise Price | $ / shares	$ 0.25
Expiration Fiscal Period	4th Qtr, 2018
Warrant 9
Outstanding	37,573,317
Weighted Average Exercise Price | $ / shares	$ 0.42
Expiration Fiscal Period	1st Qtr, 2019
Warrant 10
Outstanding	1,906,257
Weighted Average Exercise Price | $ / shares	$ 0.46
Expiration Fiscal Period	2nd Qtr, 2019
Warrant 11
Outstanding	1,080,000
Weighted Average Exercise Price | $ / shares	$ 1.16
Expiration Fiscal Period	3rd Qtr, 2019
Warrant 12
Outstanding	2,603,000
Weighted Average Exercise Price | $ / shares	$ 1.15
Expiration Fiscal Period	4th QTR, 2019
Warrant 13
Outstanding	505,000
Weighted Average Exercise Price | $ / shares	$ 0.92
Expiration Fiscal Period	1st Qtr, 2020
Warrant 14
Outstanding	1,704,446
Weighted Average Exercise Price | $ / shares	$ 0.19
Expiration Fiscal Period	4th Qtr, 2020
Warrant 15
Outstanding	6,836,016
Weighted Average Exercise Price | $ / shares	$ 0.12
Expiration Fiscal Period	1st Qtr, 2021
Warrant 16
Outstanding	2,818,751
Weighted Average Exercise Price | $ / shares	$ 0.09
Expiration Fiscal Period	2nd Qtr, 2019
Warrant 17
Outstanding	133,334
Weighted Average Exercise Price | $ / shares	$ 7.05
Expiration Fiscal Period	4th Qtr, 2020