Cost of Grant Revenues. Cost of grant revenues for the six months ended June 30, 2021 and 2020 was $326,766 and $6,515, respectively. The cost of grant revenues relates to the subcontract with DTI discussed above and are equal to the associated grant revenues resulting in no gross profit. We expect no gross profit under the subcontract with DTI or from other grants that we are pursuing or may pursue in the remainder of 2021.
Research and Development Expenses. Research and development expenses increased by $154,584, or 23%, to $821,573 in the six months ended June 30, 2021 from $666,989 in the six months ended June 30, 2020. The increase was due to higher contract labor for driver development and the expansion of internal test capabilities of $125,899, an initial license fee of $50,000 for the right to certain semiconductor technology and higher other B-TRAN™ spending of $16,675, partly offset by lower stock-based compensation expense of $37,990. We expect higher quarterly research and development expenses, as compared to the three months ended June 30, 2021, for the remainder of 2021 as we accelerate development of our B-TRAN™ technology. Research and development expenses will be subject to quarterly variability due primarily to the timing of semiconductor fabrication costs.
General and Administrative Expenses. General and administrative expenses increased by $108,556, or 10%, to $1,204,204 in the six months ended June 30, 2021 from $1,095,648 in the six months ended June 30, 2020. The increase was due to higher investor relations spending of $153,320, a $110,117 higher bonus accrual, primarily related to bonuses approved by the Board for successful completion of the February 2021 Offering (as defined below), and professional services paid in stock of $68,680, partly offset by CEO search fees in the first six months of 2020 of $137,968, lower stock-based compensation expense of $71,699 and lower other costs of $13,894. We expect general and administrative expenses to be relatively flat to modestly down, as compared to the three months ended June 30, 2021, for the remaining quarters of 2021.
Sales and Marketing Expenses. Sales and marketing expenses were $174,611 in the six months ended June 30, 2021. We did not have sales and marketing expenses in the six months ended June 30, 2020. The increase was due primarily to the hiring of a Vice President of Business Development in the first quarter of 2021 and related expenses. We expect higher sales and marketing expenses, as compared to the three months ended June 30, 2021, for the remaining quarters of 2021 as we engage with prospective customers and thereby begin to commercialize our B-TRAN™ technology.
Loss from Operations. Our loss from operations for the six months ended June 30, 2021 was $2,200,388 or 25% higher than the $1,762,637 loss from operations for the six months ended June 30, 2020 for the reasons discussed above.
Other (Income) Expenses. Other income was $89,545 for the six months ended June 30, 2021 compared to other expenses of $1,122 for the six months ended June 30, 2020. The other income in the six months ended June 30, 2021 was due to a $91,407 gain on the forgiveness of our PPP Loan in May 2021.
Net Loss. Our net loss for the six months ended June 30, 2021 was $2,110,843, or 20% higher, as compared to a net loss of $1,763,759 for the six months ended June 30, 2020, for the reasons discussed above.
Liquidity and Capital Resources
We currently generate grant revenue only and expect grant revenue to be our only source of revenue for 2021. We have incurred losses since inception. We have funded our operations to date through the sale of common stock and warrants.
At June 30, 2021, we had cash and cash equivalents of $25,716,977. Our net working capital at June 30, 2021 was $25,242,612. We had no outstanding debt at June 30, 2021.
Operating activities in the six months ended June 30, 2021 resulted in cash outflows of $1,801,095, which were due primarily to the net loss for the period of $2,110,843 and a non-cash gain on loan forgiveness of $91,407, partly offset by stock-based compensation of $153,644, favorable balance sheet timing of $107,960, depreciation and amortization of $70,343 and stock issued for services of $68,680. Operating activities in the six months ended June 30, 2020 resulted in cash outflows of $1,497,357, which were due to the loss from continuing operations for the period of $1,763,759 and unfavorable balance sheet timing of $85,249 partly offset by stock-based compensation of $226,168, depreciation and amortization of $57,248, stock issued for services of $50,000 and patent impairment charges of $18,235. We expect a ramp up in cash outflows from operating activities for the remainder of 2021 as we accelerate development and commercialization of our B-TRAN™ technology.