Pack in all the math, chemistry and physics you can to your curriculum...from here forward. Of course, you'll be majoring in biology, but these other science will be critical. Also, become very familiar with computers, computer science and software, especially CAD software.
While you're doing all that, find a tech company with whom you can intern so you can begin making connections and building a network.
This field will become even more important as our endless wars keep producing an endless stream of disabled veterans. They will be best served by better prostheses and devices that try to make their lives worth living after war.