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 $103,581 for the six months ended June 30, 2021 as compared to $23,173 in the same period in 2020, an increase of $80,408. The overall increase in other expenses was primarily the result of an increase in foreign exchange losses of $61,324 and a decrease of $13,641 in investment interest income, as interest rates on average were lower in the six months ended June 30, 2021 as compared to the same period of 2020.
Provision for Income Taxes. There was not a provision for income taxes in the respective six-month periods ending June 30, 2021 and 2020.
Liquidity and Capital Resources
Capital Resources: As of June 30, 2021, we had cash and cash equivalents of $137,604,345, an increase of $101,534,837 from $36,069,508 as of December 31, 2020.
As of June 30, 2021, we had current assets of $151,034,994 as compared to current liabilities of $3,128,923 which resulted in a positive working capital position of $147,906,071. 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 six months ended:
| | | | | | | | | |
| | June 30, | | June 30, |
| | 2021 | | 2020 |
Net Cash Provided by (used in) | | | | | | |
Operating Activities | | $ | (13,108,703) | | $ | (8,871,081) |
Investing Activities | | | (1,238,772) | | | (644,037) |
Financing Activities | | | 115,882,312 | | | 12,138,209 |
During the six months ended June 30, 2021, we used a net $13,108,703 of cash for operating activities as compared to $8,871,081 for the comparable period in 2020. For the six months ended June 30, 2021, we incurred a net loss of $15,418,820, which after adding back non-cash operating expenses of $6,965,282, resulted in a net cash loss of $8,453,538 before changes in working capital. For the six months ended June 30, 2020, we had a net cash loss of $7,219,908 before changes in working capital. Net changes in working capital items were $4,655,165 for the six months ended June 30, 2021 with the largest factor resulting from $4,348,612 of investments in inventory and vendor prepayments for M400 components and $522,084 for prepaid insurance premiums; partially offset by a decrease in accounts receivable of $289,567.
During the six months ended June 30, 2021, we used $1,238,772 of cash for investing activities, which includes $719,164 for purchases of manufacturing equipment and product mold tooling; $214,450 in patent and trademark expenditures and a $200,000 equity investment in a strategic business partner. For the six months ended June 30, 2020, we used a total of $644,037 in cash for investing activities.
During the six months ended June 30, 2021, we received $115,882,312 in net cash from financing activities, which included: (i) $91,647,850 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) $673,760 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 employee stock awards in 2020 that were granted as part of our salary reduction program, which vested in January 2021, whereby the