Yuliang, my advice to you and to any other serious student is to forget about this technology for a few years at least. Concentrate on what you have chosen as your goal: learning and applying mathematics. If you spend time on Eink displays, obtaining/converting/formatting files for the device, figuring out solutions to their poor searching and note-taking capabilities, etc., then you will spend a lot of your precious time fooling with cool technologies but not with math. I have two daughters in college and together we got interested in replacing textbooks and handwritten notes with ebooks and electronic notes. It became very clear to me that although this sounds like the correct ultimate solution, it's not ready for use by people who need to think about the problem they're working on instead of the tools and the medium they're using to work on it. Books, papers, pencils are all archaic but they just work without you having to think about them.
If you go ahead with this idea anyway, then I strongly suggest a tablet pc since it will give you far fewer problems than the Eink devices, you can take notes in Mathematica (if you insist on avoiding paper), refer to publications on the web, have multiple open windows for when you are trying to read and refer to other documents, you can search, you can take notes, etc. You will still have to deal with the vagueries of the software that captures your writings, the OCR software, the managing of your note files, the reliability of the touchscreen, and planning for lost data. But you will have much more serious problems, I think, if you try to use something less than a full-blown tablet pc and you will have probably spent a lot of time before deciding it was the wrong thing to do.
Best of luck to you!
