Battery-free toothbrush is powered with a twist
Battery-powered toothbrushes are convenient if you don't like brushing your teeth the old-fashioned way, but they have a catch: batteries. Typically, you either need to dock your brush (and remember to carry a charger with you on long trips) or toss disposables when they're done. There might be a better way soon, though: Goodwell Co. is crowdfunding Be, which it bills as the first battery-free powered toothbrush. Twist the base twice and a kinetic energy storage mechanism will vibrate the brush head for up to 2 minutes...