How much of a share should I have in a startup based on my PhD research? I am about to conclude my Ph.D. work. The research has led to a possible commercial product which I always pushed. So now, after four years of work, we've filed four patents with three already granted. A year and a half ago, the PI moved to another position, so now I communicate my progess once a month). 

I developed the scientific product along with software, electronic hardware, web apps, and so on, not to mention journal papers on the way. The technology is promising and we have businesses interested and willing to invest. 
Along the way we got a part-time master's business student, who supports us when we have to write proposals and do interview calls and meeting possible business leads. I always join those meetings and often take decision on what should be the way and what is achievable. 

Now we are on the verge of legally founding the company and possibly soon begin sales. 

My dilemma is finding out what share of the company is fair for me. 

The partners in the business would be me, the business student, and my PI. (I think the PI should get a fair share; after all, it was research done in her lab, however I have seen opinions saying this should be no more than 10 percent.)

Of course, on the way, there were master's student with whom I worked and taught them the lab work and tricks and all that I could to have them their work done in timely manner, also I offered them opportunity to be part of startup but they were not interested. 

I don't want it to be a quarrel but also don't want to feel exploited. 
If I leave there is no one on the team who understands how the technology works, or how we can produce with alternative methods (I might be overestimating, but this stuff I did for my PhD and mostly it would be another PhD who could do it. It is countless hours of labwork.) I am a co-inventor along with PI on all the patents filed/granted. 

Please help me out in figuring what share of the company I should expect.
TL,DR: You deserve a large majority.  I consider 90% for you and 10% for your professor fair.

I finished my Ph.D. and co-founded a company based on dissertation work. I continue to work as a funded tech entrepreneur.  I offer the following insights:


From your situation, it sounds like no one else is remotely close to your level of contribution. If you leave, there is no business.  
Equity should be determined based on real contribution to the enterprise.  You aren't being cruel or disrespectful by placing a value on what people bring to the table. At this point of the business, value equals cash or know-how. Do not award equity to someone who's really eager and ready to "work like a dog" (chances are they will fade in six months) without tying their effort to a vesting period -- they don't receive their equity until after a period of satisfactory work, quantified and agreed-to in writing. 
As co-author of the patents, your professor is entitled to proceeds from the use of the intellectual property, but not equity. In this case, you are choosing to give equity in exchange for permission to use the patent.  Your business operating agreement should state that.
You need to check the university guidelines regarding use of the patent. Most likely, the patent is controlled by the university and you'll have to work out a licensing agreement.


When all is said and done, you need to have enough cushion to absorb dilution (if you bring on investors or high-level staff), yet retain control or a profitable equity position. I think a 90%-10% split between you and your professor is about right at this point. If you bring on the business student (they may be a nice person, but aren't providing a lot of value), I propose a 85%-10%-5% split with a vesting period for the student.  Consider awarding more equity to the student later if they work hard.

Good luck and remember: you have the know-how if people decide to make things difficult.  Walk away if needed.