A breakthrough in wireless technology could allow a new wave of health tracking tools that can be embedded inside our bodies – in our livers, hearts and even in our brains. A new wireless charging technique known as “mid-field wireless transfer” can deliver power to tiny electronic devices such as sensors, pacemakers and nerve stimulators embedded deep within the body. They can be charged using a device the size of a credit card placed outside the body. “With this method, we can safely transmit power to tiny implants in organs like the heart or brain, well beyond the range of current near-field systems,” said Dr John Ho, co-author of the study that appears in the Proceedings of the National Academy of Sciences. Sensors can be embedded deeper into the right areas of the body, without needing to be close to the skin for current near-field wireless charging technologies like those that charge electric toothbrushes.