In an effort to make the batteries that power wearables and medical gadgets less rigid and safer, researchers have created new, flexible batteries. Today, these new batteries are run on saltwater. Questions are now being asked, however, on why not use blood and tears?
Batteries work by storing electrical energy as chemical energy. They have three fundamental components: two metal electrodes that conduct electricity – the cathode, positively charged, and the anode, negatively charged – and a paste of electrolytes in the middle. When the battery is in use, ions shed their electrons and float through the electrolyte from one electrode to the other.
The new flexible and lightweight batteries can withstand being folded in half a hundred times, and, crucially, they are safe! Instead of using the common strong acids or toxic chemicals, the batteries are fuelled by relatively safe liquids like saltwater and IV rehydration solutions. That is essential for battery powered devices that are worn on or inside your body. Surely, no one wants corrosive, flammable, or toxic materials leaking onto their skin?! Because of this, it is essential to move away from historic materials, into using something much less harmful.
These flexible batteries come in two unique forms. One is a belt-shaped battery, made of two compacted electrodes that sandwiching the electrolyte between. The other is a fibre-shaped battery that has carbon nanotube electrodes embedded with cathode and anode nanomaterials. These are pressed together into a tiny, hollow tube filled with an electrolytic solution. The idea is that these thread-like batteries could one day be woven into wearables or smart clothing. During testing, both batteries outperformed most lithium-ion batteries that are currently used in wearables. This was in both power output and the amount of charge they can hold.
The best performing electrolyte was sodium sulfate. However, some tests with a few different biologically friendly electrolytes have been tried. But saline solutions, which are literally diluted salt water, also did well.
Not only did the concept batteries outperform traditional batteries, the nanotube fibre version accelerated the conversion of dissolved oxygen into hydroxide ions. In simple words, it starved the electrolyte of oxygen. Even though this reduces the battery’s effectiveness, deoxygenation is perfect for cancer starvation therapy.
The hypothesis is to implant these fibre-shaped electrodes into the human body to consume oxygen. Deoxygenation might even wipe out cancerous cells or pathogenic bacteria since they are very sensitive to changes in living environment pH. At present, however, this still requires further research.
The batteries have not yet been tested with actual medical devices. Low voltage is an inherent drawback of safe, aqueous batteries. However, the work is still at an initial research stage, and technological improvements are needed for practical applications.
Another recent innovation is a paper-based battery that is powered by the bacteria in saliva. With just one drop of spit, this innovation can power a single LED light for about 20 minutes!
So there may come a day when all we will need to power up our phones with our blood, sweat, or tears. You know what that means, right? Go ahead and cry or just spit on it!