Note 7 - Financial Instruments	3 Months Ended
Mar. 31, 2022
Notes to Financial Statements
Financial Instruments Disclosure [Text Block]	7. Financial Instruments 2016 Warrant On September 2, 2016, the Company entered into a loan and security agreement (as amended from time to time, the “Loan Agreement”) with OCM Strategic Credit SIGTEC Holdings, LLC (“Lender”). The Company voluntarily prepaid this Loan Agreement in 2020. Upon such prepayment and release, the Loan Agreement was terminated. In connection with the entry into the Loan Agreement, the Company issued a warrant (the “Warrant”) to the Lender on September 2, 2016 to purchase a number of shares of the Company’s common stock equal to $4.0 million divided by the lower of (i) $2.29 per share and (ii) the subscription price paid in connection with the Rights Offering. The Warrant provides for weighted average anti-dilution protection and is exercisable in whole or in part for ten (10) years from the date of issuance. The per share subscription price paid was $1.50 in connection with the Rights Offering; accordingly, the exercise price of the Warrant was set at $1.50 per share, and there were 2.7 million shares underlying the Warrant. Taking into account partial exercises of the Warrant, there were approximately 1.0 million shares underlying the outstanding Warrant as of March 31, 2022. The Company accounts for the Warrant in accordance with the authoritative guidance, which requires that free-standing derivative financial instruments with certain anti-dilution and cash settlement features be classified as assets or liabilities at the time of the transaction and recorded at their fair value. Any changes in the fair value of the derivative instruments are reported in earnings or loss as long as the derivative contracts are classified as assets or liabilities. The Company classified the Warrant as a liability and reports the change in fair value in the statement of operations. Under the terms of the Warrant, in the event of a declaration of a cash dividend, the Lender is entitled to receive a cash payment that is equivalent to the dividend that would have been received if the Warrant had been fully exercised immediately prior to the dividend record date. As of March 31, 2022, the fair value of the Warrant was $6.2 million. The fair value of the liability-classified Warrant was calculated using the following assumptions: risk free interest rate of 2.43%; no dividend yield; an expected life of 4.4 years; and a volatility factor of 60%. As of December 31, 2021, the fair value of the Warrant was $6.5 million. The fair value of the liability-classified Warrant was calculated using the following assumptions: risk free interest rate of 1.21%; no dividend yield; an expected life of 4.7 years; and a volatility factor of 55%.

Note 7 - Financial Instruments

3 Months Ended

Mar. 31, 2022

Financial Instruments Disclosure [Text Block]

2016 Warrant

On September 2, 2016, the Company entered into a loan and security agreement (as amended from time to time, the “Loan Agreement”) with OCM Strategic Credit SIGTEC Holdings, LLC (“Lender”). The Company voluntarily prepaid this Loan Agreement in 2020. Upon such prepayment and release, the Loan Agreement was terminated. In connection with the entry into the Loan Agreement, the Company issued a warrant (the “Warrant”) to the Lender on September 2, 2016 to purchase a number of shares of the Company’s common stock equal to $4.0 million divided by the lower of (i) $2.29 per share and (ii) the subscription price paid in connection with the Rights Offering. The Warrant provides for weighted average anti-dilution protection and is exercisable in whole or in part for ten (10) years from the date of issuance. The per share subscription price paid was $1.50 in connection with the Rights Offering; accordingly, the exercise price of the Warrant was set at $1.50 per share, and there were 2.7 million shares underlying the Warrant. Taking into account partial exercises of the Warrant, there were approximately 1.0 million shares underlying the outstanding Warrant as of March 31, 2022.

The Company accounts for the Warrant in accordance with the authoritative guidance, which requires that free-standing derivative financial instruments with certain anti-dilution and cash settlement features be classified as assets or liabilities at the time of the transaction and recorded at their fair value. Any changes in the fair value of the derivative instruments are reported in earnings or loss as long as the derivative contracts are classified as assets or liabilities. The Company classified the Warrant as a liability and reports the change in fair value in the statement of operations.

Under the terms of the Warrant, in the event of a declaration of a cash dividend, the Lender is entitled to receive a cash payment that is equivalent to the dividend that would have been received if the Warrant had been fully exercised immediately prior to the dividend record date.

As of March 31, 2022, the fair value of the Warrant was $6.2 million. The fair value of the liability-classified Warrant was calculated using the following assumptions: risk free interest rate of 2.43%; no dividend yield; an expected life of 4.4 years; and a volatility factor of 60%.

As of December 31, 2021, the fair value of the Warrant was $6.5 million. The fair value of the liability-classified Warrant was calculated using the following assumptions: risk free interest rate of 1.21%; no dividend yield; an expected life of 4.7 years; and a volatility factor of 55%.