Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2022

Equity Incentive Plans [Abstract]

Stock Option Plan Activity

Activity under the stock option plans was as follows:

				Weighted
				average
	Number of			exercise
	options			price
Balances at December 31, 2020		743,627		$	3.60
Granted		—			—
Exercised		(44,698	)		2.83
Expired		(556	)		27.00
Forfeited		(8,378	)		5.43
Balances at December 31, 2021		689,995		$	3.58
Granted		367,670			5.33
Exercised		(9,445	)		1.71
Expired		(10,558	)		27.00
Forfeited		(106,112	)		4.09
Balances at December 31, 2022		931,550		$	3.97

Stock options granted under the stock option plans for the years ended December 31 2022 and 2021 were as follows:

	2022		2021
Employee		299,670		—
Nonemployee		68,000		—
Total		367,670		—

Options Outstanding and Vested and Currently Exercisable by Exercise Prices

The options outstanding and vested and currently exercisable by exercise prices as of December 31, 2022 were as follows:

Option outstanding						Options vested and exercisable
				Weighted				Weighted		Weighted
				average		Number of		average		average
Exercise		Outstanding		remaining		options		Exercise		remaining
price		(in shares)		life years		vested		price		life years
$	1.13 - 1.67		91,100		9.59		—	$	—		—
	1.68 - 1.86		193,335		3.21		82,224		1.71		3.21
	1.87 - 3.14		166,850		9.09		—		—		—
	3.15 - 3.60		259,836		4.50		259,836		3.24		4.50
	3.61 - 5.31		68,616		5.23		68,616		3.97		5.23
	5.32 - 9.56		51,813		6.95		38,765		6.12		6.95
	9.57 - 13.00		100,000		9.07		—		—		—
			931,550		6.23		449,441		3.32		4.58

Black-Scholes Weighted Average Assumptions

The Black-Scholes weighted average assumptions for all stock option awards granted during 2022 were as follows:

	2022
	2021 Equity Plan			Inducement Grants
Fair Value of Awards	$	2.06			2.01
Grant Price	$	5.33			2.42
Expected term (in years)		6.28			6.25
Risk‑free interest rate		2.13	%		2.52	%
Dividend yield		—	%		—	%
Expected volatility		107.98	%		107.70	%

Share-based Compensation Expense

The following table shows the stock-based compensation expense related to vested stock option grants to employees and nonemployees awarded under the stock plans and inducement grants by financial statement line item on the accompanying statement of comprehensive loss:

	2022		2021
Research and development	$	95,484		106,469
Sales and marketing		6,680		3,759
General and administrative		122,775		83,138
Total share-based compensation expense	$	224,939		193,366