Jan 28 (Reuters) - Elon Musk's brain implant company Neuralink said on Wednesday it now has 21 total participants enrolled in trials worldwide, as it completes two years since it officially began testing on humans.

Elon Musk said Tesla Inc. needs to build and operate what he is calling a “TeraFab” to manufacture semiconductors, a massive undertaking that will cost billions of dollars and mark another expansion beyond what had been the company’s core electric vehicle business.

The billionaire CEO of Tesla and SpaceX, in his first appearance at Davos, said Tesla could start selling its Optimus robots next year.

Regulators said the company’s lack of controls had led to the widespread use of deepfakes created with the chatbot Grok.

The Tesla call has wrapped up and investors kept their focus on the eye-popping $20 billion capex number. Musk said that the company is making sure it can not only "scale to very high volume with autonomous vehicles,

Telsa’s revenue and profits tumbled in the fourth quarter, capping off the most difficult year for the electric automaker since it became profitable six years ago.