writing about my motivations to make the essay sound a bit emotional.
What do you mean? For sure, you should write about your motivations in one way or another.
you clearly should avoid stating your accomplishments and activities, right? =)
Great advice, Moon Dan.
What this essay is... it is your self-expression. You get to express the ideas you have gained by reading a lot of books and articles associated with your chosen field. Some kids to not read about the advancements in their chosen field, and those kids are not so serious. Your job right now is to prove that you have something to say, prove that you have ideas.
So... it is up to you. It all depends on how much you have read. And if you feel unprepared, you should go find 3 things to read before starting the essay. i.e. things written by people in the field of biomed engineering.