Battery-Free Medical Implants

Nearly all of the implantable medical devices in use today have one thing in common – they require some form of battery to function. Over time, these batteries inevitably need to be replaced, necessitating repeat surgeries that can be painful and risky. But researchers have now developed a new type of power source that could eliminate the need for batteries altogether. Known as a “biological supercapacitor,” it harnesses electricity from the electrolytes in biological fluids (like blood and urine) to enable lifelong, battery-free operation of implantable devices such as pacemakers, defibrillators and glucose monitors.

The new “biosupercapacitor” contains a non-toxic, protein-modified graphene oxide electrode while the biological fluids form the electrolyte. The entire structure is only one micrometer thick, yet is strong and flexible enough to withstand the mechanical stresses caused by twisting and turning inside the body. The energy density is comparable to lithium thin film, but it contains none of the toxic chemicals present in traditional batteries.

The supercapacitor is combined with an energy harvester – a device that converts heat and motion into electricity, similar to the way a self-winding watch generates power from the wearer’s movement. Used in tandem, they create a virtually endless source of power that could be used for a variety of implantable devices.