Water Logo Design

I graduated with a B.A in graphic design in 2006. However my perspective about things have changed very much. I know I would definitely like to go back to school and get a degree in industrial design but I’ve always wanted to invent things that people could actually use. I’m starting to feel more strongly about that goal everyday. I have ideas to improve the quality of wheelchairs, crutches, grocery carts, providing devices for people w/ memory loss or alzeimers, and also devices to assist areas with clean water even during droughts. I’m interested in many different areas but instead of making posters and logos, I want to create things people can benefit from while also being environmentally safe. I know this involves engineering but it’s so broad i’m not sure which branch I would fall into.