Friction Boosts sound very efficient Hannah. It's vital that we have budding new inventors to create sustainable energy sources that will positively impact our environment - minds like yours! Your invention would make use of the energy we create anyway by walking and save having to continually buy new batteries for small items. It's so annoying when something runs out of charge but you don't have any spare batteries in the house, Friction Boosts would solve this problem! You have designed your picture beautifully, I love the rainbow sole and the fact that the materials are recycled. I'm glad you made a size large, I have big feet too! Keep up the great work!