The following table presents stock-based compensation expenses included in our unaudited consolidated statements of operations and comprehensive income (loss) (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Cost of sales	$	7	$	5	$	19	$	13
Research and development		54		67		229		169
Selling and marketing		182		74		260		176
General and administrative		305		295		848		719
Stock-based compensation expense	$	548	$	441	$	1,356	$	1,077

Stock Options - We did not grant stock options in the three or nine months ended September 30, 2022. We granted stock options for 0 and 2,875,000 shares in the three months and nine months ended September 30, 2021, respectively.

Unrestricted Stock Grants - We grant unrestricted shares of stock under our 2001 Nonqualified Stock Plan. Stock-based compensation expense for stock grants is determined based on the fair market value of our stock on the date of grant, provided the number of shares in the grant is fixed on the grant date.

In the three and nine months ended September 30, 2022 we granted an aggregate of 60,000 and 167,921 shares of unrestricted stock, respectively. Of these shares 61,459 vested and 54,167 shares where issued in early July 2022 after employees surrendered 7,292 shares for payment of withholding taxes on their behalf. Of the remaining 106,462 shares of unrestricted stock granted in 2022, 46,462 are scheduled to vest and be issued shortly after December 31, 2022, provided each grantee is serving as a director, officer or employee on that date. The remaining 60,000 shares will vest and be issued in equal installments on February 9, 2023 and August 9, 2023, 2024 and 2025, provided each grantee is serving as a director, officer or employee on those dates.

Total stock-based compensation expense related to these grants is $0.5 million, of which $0.1 million and $0.3 million was charged to expense in the three and nine months ended September 30, 2022, respectively. We anticipate that of the remaining $0.2 million will be charged to expense in the fourth quarter of 2022 and the remaining balance of $0.1 million will be expensed ratably over the remaining vesting period that ends in August 2025.

In the three and nine months ended September 30, 2021 we granted an aggregate of 0 and 56,533, respectively, shares of unrestricted stock to directors. The shares were issued in two equal installments shortly after June 30, 2021 and December 31, 2021. Total stock-based compensation expense related to these grants is $0.3 million, of which $0.1 million and $0.2 million was charged to expense in the three and nine months ended September 30, 2021, respectively. The remaining $0.1 million was charged to expense in the forth quarter of 2021.

We also granted 80,000 shares of unrestricted stock to an executive officer in September 2019 to be issued in four equal installments shortly after their anniversaries of their grant dates, provided the grantee is serving as a director, officer, or employee on those dates. $13 thousand of stock based compensation expense related to this grant was charged to expense in each of the three months ended September 30, 2022 and 2021, and $42 thousand was charged to expense in each of the nine months ended September 30, 2022 and 2021. We anticipate the remaining $53 thousand will be charged to expense ratably over the remaining vesting period that ends in September 2023.

We also granted 40,000 shares of unrestricted stock to an executive officer in October 2019 to be issued in four equal installments shortly after their anniversaries of their grant dates, provided the grantee is serving as a director, officer, or employee on those dates. We issued 30,000 shares in equal installments in October 2020 and 2021 and September 2022. The remaining 10,000 where cancelled when the executive officer's employment with us was terminated in August 2022. As part of the grantee's 2019 employment agreement and in connection with the termination of the grantee's employment, vesting of the remainder of the grant was accelerated by one year and we issued the October 2022 installment in September 2022 and cancelled the remaining 10,000 shares that were to vest in October 2023. $7 thousand of stock based compensation expense related to this grant was charged to expense in each of the of the three months ended September 30, 2022 and 2021, and $22 thousand was charged to expense in each of the nine months ended September 30, 2022 and 2021.

Share Purchases - On March 1, 2022, our Board of Directors authorized a new stock repurchase program pursuant to which we may purchase up to $10.0 million of our common stock, of which $0.2 million has been repurchased as of September 30, 2022. During the three and nine months ended September 30, 2022, we purchased 75,407 and 76,561 shares of our common stock, respectively. The shares may be purchased from time to time in the open market or through privately negotiated transactions at management’s discretion, depending upon market conditions and other factors. The authorization to repurchase shares of our common stock expires on December 31, 2023. Repurchases will be made under the program using our own cash resources and will be in accordance with Rule 10b5-1 under the Securities Exchange Act of 1934, and other applicable laws, rules and regulations, which may permit repurchases to occur during periods when we might otherwise be precluded from making purchases under insider trading laws or company policy. The program does not obligate us to acquire any particular amount of common stock and the program may be modified or suspended at any time at our Board of Director’s discretion.