I finished my PhD in Mechanical from UIUC in 2010, so I think I can give you some advice that helped me out after going through the entire process. I'll echo that you sound like you are early in your undergrad, so don't fall into a trap of trying to decide something too soon. However, kudos for thinking about this already! Your early preparation will hopefully increase your chances of getting to do what you like.
My second piece of advice is to not start looking at what schools you want to go to first. If you want to do PhD research, start looking at future advisors/professors that you would like to be mentored by who are active in the fields that you are interested in researching. Your relationship with your advisor and what you work on day-to-day are much, much, much (is that too many much's?) more important than the name of the school. I applied to several of the schools that you mentioned but ended up at UIUC because it was one of only two schools in the US that I found was doing research in the areas that I was interested in pursuing as well.
Most schools have lists of faculty and their research interests listed (e.g. http://mechanical.illinois.edu/directory/faculty) often with links to a prof's home page. Although these rarely are kept up to date, you may be able to get some emails from grad students who are working with the professor. They are more likely to respond to your questions than a professor will be. (If a prof does reply to you, that is a really good sign too).