Balance Sheet Components	12 Months Ended
	Dec. 31, 2021
Balance Sheet Components [Abstract]
Balance Sheet Components	4. Balance Sheet Components InventoryInventory consisted of the following (in thousands): Year Ended December 31, 2021 2020Raw materials $ 2,010 $ —Work in process 1,371 —Finished goods 2,443 — Total inventory $ 5,824 $ — Property and Equipment, net Property and equipment, net consisted of the following (in thousands): December 31, 2021 2020Leasehold improvements $ 2,519 $ 2,805Laboratory equipment 1,019 878Furniture, fixtures and equipment 932 517Software 202 128Construction in progress 186 66 4,858 4,394Less: Accumulated depreciation and amortization (2,396) (1,916) $ 2,462 $ 2,478 The lease for the Company’s current premises in Hayward, California began in July 2017, per terms of the lease, the landlord provided $2.1 million in tenant improvement allowance which was capitalized. Depreciation expense for the years ended December 31, 2021, 2020, and 2019 was $0.5 million, $0.4 million, and $0.5 million, respectively. Intangible Assets, net Intangible assets primarily consist of a license to utilize certain patents, know-how and technology relating to the Company’s NPS for biomedical applications acquired from Old Dominion University Research Foundation (ODURF), Eastern Virginia Medical School (EVMS), and the University of Southern California. In addition, the Company entered into a sponsored research agreement (“SRA”) with Old Dominion University’s Frank Reidy Research Center for Bioelectrics, a leading research organization in the field, which includes certain intellectual property rights arising from the research. The Company is amortizing the intangible assets over an estimated useful life of 12 years. Intangible assets, net consisted of the following (in thousands): December 31, 2021 2020Acquired patents and licenses $ 7,985 $ 7,985Less: Accumulated amortization (4,769) (4,103) $ 3,216 $ 3,882 A schedule of the amortization of intangible assets is as follows (in thousands): Years ending December 31: 2022 $ 6652023 6652024 6652025 6652026 556 $ 3,216 Accrued Expenses Accrued expenses consisted of the following (in thousands): December 31, 2021 2020Compensation expense  $ 2,932 $ 3,324Controlled launch (Note 8) 534 —Director and officer liability insurance (Note 12) — 1,563Clinical trial fees and costs   245 188Professional fees   85 87Warranty 80 —Other   513 164   $ 4,389 $ 5,326