Neuralink, the start-up co-founded by the billionaire Elon Musk, has taken steps to sell as much as US$100 million in stock to fund the development of technology that connects human brains with computers. The San Francisco-based company has already got $27m in funding, according to a filing with the US securities and exchange commission. Mr Musk said via Twitter on Friday that Neuralink is not seeking outside investors. A spokesman did not respond to questions about the source of the funds. Mr Musk is the chief executive of Tesla and Space Exploration Technologies and has several other pet projects, including a venture to bore tunnels for roads or tube-based transportation systems known as the hyperloop, and another project for the responsible development of artificial intelligence. In June, he said Neuralink is a priority after much more demanding commitments to his automotive and rocket companies. “Boring is maybe 2 per cent of my time; Neuralink is 3 per cent to 5 per cent of my time; OpenAI is going to be a couple of per cent; and then 90-plus per cent is divided between SpaceX and Tesla,” said Mr Musk at the electric-car maker’s annual shareholder meeting. Few details are known about Neuralink. The company’s sparse website says it’s “developing ultra-high bandwith brain-machine interfaces to connect humans and computers.” It’s also recruiting engineers and scientists to join the effort. “No neuroscience experience is required: talent and drive matter far more,” the company says on the site. “We expect most of our team to come from other areas and industries.”