Share-based payments (Details 3) - USD ($)
|
1 Months Ended |
12 Months Ended |
Dec. 21, 2017 |
Dec. 31, 2019 |
Dec. 31, 2018 |
| Number of Warrants |
|
|
|
| Granted |
|
|
5,431,944
|
| Exercised |
120,000
|
|
|
| Forfeited or expired |
|
(6,853,719)
|
(501,645)
|
| Weighted Average Exercise Price |
|
|
|
| Granted |
|
|
$ 0.06
|
| Forfeited or expired |
|
$ 0.56
|
$ 0.29
|
| Nonemployee common stock warrants - Fully-vested upon issuance [Member] |
|
|
|
| Number of Warrants |
|
|
|
| Shares Outstanding, Beginning |
|
13,445,836
|
12,945,836
|
| Granted |
|
2,100,000
|
500,000
|
| Exercised |
|
|
|
| Forfeited or expired |
|
(5,810,000)
|
|
| Shares Outstanding, Ending |
|
9,735,836
|
13,445,836
|
| Shares Exercisable, Ending |
|
9,735,836
|
13,445,836
|
| Weighted Average Exercise Price |
|
|
|
| Per share Outstanding, Beginning |
|
$ 0.27
|
$ 0.29
|
| Granted |
|
0.004
|
0.05
|
| Exercised |
|
|
|
| Forfeited or expired |
|
0.49
|
|
| Outstanding, Ending |
|
0.39
|
0.27
|
| Per share Exercisable, Ending |
|
$ 0.39
|
$ 0.27
|
| Weighted-average Remaining Life (Years) |
|
|
|
| Outstanding, Beginning |
|
1 year 4 months 24 days
|
|
| Outstanding, Ending |
|
1 year 3 months 18 days
|
1 year 4 months 24 days
|
| Exercisable, Ending |
|
1 year 3 months 18 days
|
1 year 4 months 24 days
|
| Aggregate Intrinsic Value |
|
|
|
| Aggregate intrinsic value outstanding, Beginning |
|
$ 78,000
|
|
| Aggregate intrinsic value outstanding, Ending |
|
2,000
|
78,000
|
| Aggregate intrinsic value exercisable |
|
$ 2,000
|
$ 78,000
|