Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (33,276)	$ (28,794)	$ (22,425)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	231	221	278
Noncash interest expense	664	584	523
Amortization of intangible assets	304	304	304
Inventory excess and obsolescence charge	1,439	1,327	1,591
Change in fair value of warrants			5
Stockbased compensation expense	3,661	2,058	457
Loss on disposal of fixed assets	2
Change in operating assets and liabilities:
Accounts receivable, net	(1,553)	149	(1,528)
Inventory	(5,194)	(620)	(1,839)
Prepaid expenses and other assets	(992)	66	(1,977)
Accounts payable	1,597	(2,002)	(773)
Accrued expenses and other current and long-term liabilities	2,673	2,321	(118)
Foreign currency remeasurement loss	12	(70)	(21)
Net cash used in operating activities	(30,432)	(24,456)	(25,523)
Cash flows from investing activities:
Purchases of short-term investments			(9,284)
Proceeds from the sale and maturity of short-term investments		9,289
Payment for intangible asset			(2,500)
Purchase of property and equipment	(627)	(167)	(197)
Net cash (used in) provided by investing activities	(627)	9,122	(11,981)
Cash flows from financing activities:
Proceeds from follow-on offering, net of underwriting discounts, commissions and offering costs		44,722
Proceeds from initial public offering, net of underwriting discounts, commissions and offering costs			51,151
Proceeds from issuance of Series B redeemable convertible preferred stock, net of offering costs			14,367
Payment of initial public offering costs		(522)
Proceeds from exercise of stock options	547	175	14
Proceeds from issuance of common stock under the employee stock purchase plan	38	34
Net cash provided by financing activities	585	44,409	65,532
Effect of exchange rate on cash and cash equivalents	11	17	(4)
Net (decrease) increase in cash and cash equivalents	(30,463)	29,092	28,024
Cash and cash equivalents, beginning of year	74,394	45,302	17,278
Cash and cash equivalents, end of year	43,931	74,394	45,302
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	2,933	2,980	3,086
Supplemental disclosures of noncash investing and financing activities:
Accretion of redeemable convertible preferred stock			7,783
Conversion of convertible preferred stock to common stock in connection with the initial public offering			146,300
Conversion of outstanding preferred stock warrants			1,645
Offering costs in accounts payable and accrued expenses and other current liabilities			522
Property and equipment in accounts payable	166	3
Issuance of common stock for early exercised stock options	1	3	4
Unrealized loss on short-term investments			$ 4
Liability-classified stock-based compensation in accrued expenses and other current liabilities		$ 82
Reclassification of liability-classified stock-based compensation awards to equity-classified	$ 82