Depreciation and Amortization. Depreciation and amortization expense for the nine months ended September 30, 2021 was $1,453,367 as compared to $1,923,922 in the same period in 2020, a decrease of $470,555. The decrease in depreciation expense is primarily due to leasehold improvements in our West Henrietta, New York location, which became fully amortized in October 2020.
Other Expense. Total other expense was $219,267 for the nine months ended September 30, 2021 as compared to $35,758 in the same period in 2020, an increase of $183,509. The overall increase in other expenses was primarily the result of an increase in foreign exchange losses of $100,882 and an increase of $94,167 in income and other taxes.
Provision for Income Taxes. There was not a provision for income taxes in the respective nine-month periods ending September 30, 2021 and 2020.
Liquidity and Capital Resources
Capital Resources: As of September 30, 2021, we had cash and cash equivalents of $128,746,661, an increase of $92,677,153 from $36,069,508 as of December 31, 2020.
As of September 30, 2021, we had current assets of $143,988,078 as compared to current liabilities of $3,650,294 which resulted in a positive working capital position of $140,337,784. As of December 31, 2020, we had a working capital position of $41,959,763. Our current liabilities are comprised principally of accounts payable, accrued expenses and operating lease right-of-use liabilities.
Summary of Cash Flow:
The following table summarizes our select cash flows for the nine months ended:
| | | | | | | | | |
| | September 30, | | September 30, |
| | 2021 | | 2020 |
Net Cash Provided by (used in) | | | | | | |
Operating Activities | | $ | (18,909,428) | | $ | (11,259,877) |
Investing Activities | | | (4,340,443) | | | (1,162,592) |
Financing Activities | | | 115,927,024 | | | 26,755,236 |
During the nine months ended September 30, 2021, we used a net $18,909,428 of cash for operating activities as compared to $11,259,877 for the comparable period in 2020. For the nine months ended September 30, 2021, we incurred a net loss of $23,364,886, which after adding back non-cash operating expenses of $9,094,889, resulted in a net cash loss of $14,269,997 before changes in working capital. For the nine months ended September 30, 2020, we had a net cash loss of $10,207,144 before changes in working capital. Net changes in working capital items were $4,639,430 for the nine months ended September 30, 2021 with the largest factor resulting from $5,196,613 of investments in inventory and vendor prepayments for M400 components; partially offset by an increase in accrued expenses of $567,947.
During the nine months ended September 30, 2021, we used $4,340,443 of cash for investing activities, which includes $3,592,703 for purchases of manufacturing equipment, product mold tooling, and chip design and tooling fees; $442,582 in patent and trademark expenditures and a $200,000 equity investment in a strategic business partner. For the nine months ended September 30, 2020, we used a total of $1,162,592 in cash for investing activities.
During the nine months ended September 30, 2021, we received $115,927,024 in net cash from financing activities, which included: (i) $91,652,617 in net proceeds from our sales of equity securities that closed on March 30, 2021 and April 1, 2021, (ii) $34,705,068 in proceeds from the exercise of warrants, and (iii) $713,703 in proceeds from the exercise of stock options. The proceeds were partially offset by a: (i) $10,000,000 payment to Intel for the settlement of our accrued Series A Preferred Stock dividends, and (ii) a $1,144,366 payment for tax withholdings related to our