Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2020

Stock-based compensation [Abstract]

Stock Option Transactions

A summary of option transactions for all of the Company’s stock options during the years ended December 31, 2020, and 2019 follows: 

	Number of Stock Options			Weighted Average Exercise Price
Outstanding at January 1, 2019		4,342,765		$	2.02
Granted		875,000			2.46
Exercised		(86,250	)		1.74
Expired/forfeited		(223,477	)		6.43
Outstanding at December 31, 2019		4,908,038			1.90
Granted		400,000			1.46
Exercised		(15,000	)		1.29
Expired/forfeited		(150	)		170.00
Outstanding at December 31, 2020		5,292,888		$	1.87
Exercisable at December 31, 2020		3,442,501		$	1.87
Options expected to vest at December 31, 2020		1,850,387		$	1.86

Stock Options Outstanding and Exercisable

The outstanding options at December 31, 2020, 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 Average Exercise Price
$	1.11 - $2.00		4,185,877		7.59	$	1.47		2,918,323	$	1.43
$	2.01 - $5.00		941,000		8.67		2.52		358,267		2.61
$	5.01 - $181.00		166,011		4.54		8.07		165,911		8.03
Total			5,292,888		7.69	$	1.87		3,442,501	$	1.87

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,
	2020	2019
Risk-free interest rate	.53%	1.66%
Volatility	94%	71%
Expected dividend yield	0%	0%
Expected life	6.0 years	6.0 years

Unvested Stock Option Activity

The following table summarizes the Company’s unvested stock option activity:

	Options			Weighted Average Grant Date Fair Value
Unvested balance as of January 1, 2019		3,394,468		$	0.82
Granted		875,000			1.56
Vested		(1,265,956	)		0.78
Forfeited/expired		-			-
Unvested balance as of December 31, 2019		3,003,512		$	1.05
Granted		400,000			1.11
Vested		(1,553,125	)		0.96
Forfeited/expired		-			-
Unvested balance at December 31, 2020		1,850,387		$	1.15

Restricted Stock Unit Award

Restricted stock unit unvested are summarized in the following table:

	Number of restricted stock units			Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2019		70,049		$	2.07
Granted		77,237			2.46
Vested/settled		(60,387	)		2.07
Forfeited/expired		(9,662	)		2.07
Unvested balance at December 31, 2019		77,237		$	2.46
Granted		-			-
Vested/settled		(68,091	)		2.46
Forfeited/expired		(9,146	)		2.46
Unvested balance at December 31, 2020		-		$	-