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...

https://www.engadget.com/2017/10/31/...ee-toothbrush/