Cost of Grant Revenues. Cost of grant revenues for the nine months ended September 30, 2021 and 2020 was $447,794 and $154,302, respectively. The cost of grant revenues relates primarily to the subcontracts with DTI discussed above and are equal to the associated grant revenues resulting in no gross profit. We expect no gross profit under the subcontracts 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 $264,512, or 23%, to $1,426,049 in the nine months ended September 30, 2021 from $1,161,537 in the nine months ended September 30, 2020. The increase was due to higher contract labor for device and driver development and the expansion of internal test capabilities of $230,317 and personnel costs of $88,733, an initial license fee of $50,000 for the right to certain semiconductor technology and higher other B-TRAN™ spending of $40,813, partly offset by lower stock-based compensation expense of $145,351. We expect quarterly research and development expenses to ramp higher, as compared to the three months ended September 30, 2021,during the fourth quarter of this year and throughout 2022 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 decreased by $48,469, or 3%, to $1,705,146 in the nine months ended September 30, 2021 from $1,753,615 in the nine months ended September 30, 2020. The decrease was due to one-time CEO search fees in 2020 of $137,968, lower stock-based compensation expense of $105,538 and lower other costs of $29,746, partly offset by higher investor relations spending of $156,103 and professional services paid in stock of $68,680. We expect general and administrative expenses to be modestly higher, as compared to the three months ended September 30, 2021, for the next few quarters.
Sales and Marketing Expenses. Sales and marketing expenses were $302,859 in the nine months ended September 30, 2021 compared to $20,000 in the nine months ended September 30, 2020. The increase was due primarily to the hiring of a Vice President of Business Development in the first quarter of 2021 and subsequent spending to work towards commercializing our B-TRAN™ technology. We expect higher sales and marketing expenses, as compared to the three months ended September 30, 2021, in the future as we engage with prospective customers and commercialize our B-TRAN™ technology.
Loss from Operations. Our loss from operations for the nine months ended September 30, 2021 was $3,434,054 or 17% higher than the $2,935,152 loss from operations for the nine months ended September 30, 2020 for the reasons discussed above.
Other Income (Expenses). Other income was $84,533 for the nine months ended September 30, 2021 compared to other expenses of $3,723,346 for the nine months ended September 30, 2020. The other income in the nine months ended September 30, 2021 related primarily to a gain on forgiveness of long-term debt of $91,407. See “PPP Loan” below. The other expenses in the nine months ended September 30, 2020 related primarily to warrant inducement expense of $3,720,866. See “Early Warrant Exercise Transaction” below.
Net Loss. Our net loss for the nine months ended September 30, 2021 was $3,349,521, or 50% lower, as compared to a net loss of $6,658,498 for the nine months ended September 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 September 30, 2021, we had cash and cash equivalents of $24.5 million. Our net working capital at September 30, 2021 was $24.1 million. We had no outstanding debt at September 30, 2021.
Operating activities in the nine months ended September 30, 2021 resulted in cash outflows of $2,992,743, which were due to the net loss for the period of $3,349,521 and a non-cash gain on loan forgiveness of $91,407, partly offset by stock-based compensation of $247,512, depreciation and amortization of $113,607, stock issued for services of $68,680, favorable balance sheet timing of $17,858 and patent impairment charges of $528. Operating activities in the nine months ended September 30, 2020 resulted in cash outflows of $2,303,639, which were due to the net loss for the period of $6,658,498, partly offset by warrant inducement expense of $3,720,866, stock-based compensation of $434,782, depreciation and amortization of $86,368, stock issued for services of $50,000, patent impairment charges of $18,235 and favorable balance sheet timing of $44,608. We expect a modest ramp up in cash outflows from operating activities during the fourth quarter of this year and throughout 2022 as we accelerate development and commercialization of our B-TRAN™ technology.