Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2017

Stock-based compensation [Abstract]

Schedule of Stock Option Plans

A summary of option transactions for all of the Company's stock options during the years ended December 31, 2017 and 2016 follows:

	Number of Stock Options			Weighted Average Exercise Price
Outstanding at December 31, 2015		536,904		$	8.07
Granted		468,002			2.90
Exercised		-			-
Expired/forfeited		(104,767	)		10.35
Outstanding at December 31, 2016		900,139			5.11
Granted		101,250			1.46
Exercised		-			-
Expired/forfeited		(135,667	)		4.78
Outstanding at December 31, 2017		865,722		$	4.74
Exercisable at December 31, 2017		542,905		$	6.10
Options expected to vest at December 31, 2017		188,484		$	2.24

Schedule of Stock Options Outstanding and Exercisable

The outstanding and exercisable options at December 31, 2017, have a range of exercise prices and associated weighted remaining contractual life and weighted average exercise price, as follows:

Options Range of Exercise Prices		Outstanding Number of Shares		Weighted Average Remaining Contractual Life (years)		Weighted Average Exercise Price		Exercisable Number of Shares		Exercisable Weighted Avg. Exercise Price
$	1.29 - $5.00		483,585		8.90	$	2.58		160,867	$	2.90
$	5.01 - $10.00		372,500		7.62		6.19		372,500		6.19
$	10.01 - $181.00		9,637		5.44		56.65		9,538		56.35
Total			865,722		8.31	$	4.74		542,905	$	6.10

Schedule of Fair Value of Each Option Award Granted

The fair value of each option award granted during the period is estimated on the date of grant using the Black-Scholes option valuation model and assumptions as noted in the following table:

	Years Ended December 31,
	2017	2016
Risk-free interest rate	1.98 – 2.17%	1.51 – 2.18%
Volatility	46%-48%	50%
Expected dividend yield	0%	0%
Expected life	5.5 years	6.5 years
Estimated forfeiture rate	0%	0%