I think asking the professor to sign an NDA is fine, using the approach written by Stephan.

However, I think a better solution would be to have a meeting to determine whether the professor has the expertise needed, then offer to hire the professor as a consultant if she's willing.

Tell the professor up front that the meeting is about consulting on a project for your business. During the meeting, keep the discussion focused on questions about the professor's knowledge and experiences.

If the professor is interested, a NDA would be the next step. After the NDA is properly executed, get all the project specifications and pitfalls (even potential pitfalls) out on the table so the professor can make an informed decision about doing the work.

Your consulting contract should include a clause for what happens if the work is not completed, a detailed specification of what is to be delivered, the terms for payment, and an assignment of intellectual property (that is, any work the professor does belongs to your company). If you don't have cash to pay for the services, consider offering equity.

Please keep in mind that a NDA is a good start, but it isn't a cure-all. You still have to know if someone breaches it and you have to pay the legal fees to enforce it.

BTW, you can always go out and learn enough to make a prototype, then HIRE an expert to be your Chief Scientist if you still need them later.

I think asking the professor to sign an NDA is fine, using the approach written by Stephan.

However, I think a better solution would be to have a meeting to determine whether the professor has the expertise needed, then offer to hire the professor as a consultant if she's willing.

Tell the professor up front that the meeting is about consulting on a project for your business. During the meeting, keep the discussion focused on questions about the professor's knowledge and experiences.

If the professor is interested, a NDA would be the next step. After the NDA is properly executed, get all the project specifications and pitfalls (even potential pitfalls) out on the table so the professor can make an informed decision about doing the work.

Your consulting contract should include a clause for what happens if the work is not completed, a detailed specification of what is to be delivered, the terms for payment, and an assignment of intellectual property (that is, any work the professor does belongs to your company). If you don't have cash to pay for the services, consider offering equity.

Please keep in mind that a NDA is a good start, but it isn't a cure-all. You still have to know if someone breaches it and you have to pay the legal fees to enforce it.

BTW, you can always go out and learn enough to make a prototype, then HIRE an expert to be your Chief Scientist if you still need them later.

Edit:

The OP hasn't formed a company and isn't sure about how to proceed. This answer would only apply in the case that a company exists and the development direction is relatively clear.