I have a suggestion to make a Brain Computer Interface Stack Exchange. What is the requirement to do that?
For suggesting sites, use Area 51 (read the FAQ to know how it works). First, do a search to check whether your proposal is already proposed. If that's not the case, then at the left sidebar, select the category for your proposed site (in this case, Technology). Scroll to the bottom and click "Propose a new Technology site", and fill in the form there to propose a site.