A research team in Germany developed the world's smallest micro supercapacitor, which can be safely used in the human body. (Image Credit: Research Group Prof. Dr. Oliver G. Schmidt)


Scientists in Germany recently created the world's smallest micro supercapacitor, achieved by combining tiny electronics with origami-inspired fabrication. The micro supercapacitor, which is smaller than a speck of dust, stores the same voltage level as an AAA battery. It also utilizes crucial blood ingredients in the human body to boost its performance.


The team worked with nano-supercapacitors (nBSC) to create this energy storage device. It's extremely challenging to develop such a component, but the ultimate goal is to produce one that works safely in the human body. That way, it provides power to tiny sensors and implants instead of switching ineffective materials and corrosive electrolytes for biocompatible types.


The smallest biosupercapacitor ever developed is larger than 3mm3, but the team took a step further, making it even smaller. Overall, the build process begins with stacked polymeric layers sandwiched together with a light-sensitive photoresist material. That material functions similarly to a current collector, separator membrane, and electrodes comprised of an electrically conductive biocompatible polymer called PEDOT:PSS.


Then, the team placed the stack on a wafer-thin surface under high mechanical tension, causing each layer to detach in a controlled manner. This causes the strain energy to release, forcing each layer to fold up like origami into a 0.001mm3 volume nano-biosupercapacitor with high accuracy and yield (95%). This entire process forms tubular biosupercapacitors with the same voltage as an AAA battery. These are 3,000 times smaller than the earlier versions.


Afterward, the team tested their devices in saline, blood plasma, and blood, where they exhibited energy storage capabilities. In blood, the nano-biosupercapacitor managed to retain 70% capacity even after 16 hours. Blood is ideal because the team's device functions with redox enzymatic reactions and living cells in the solution. From there, the device can supercharge its charge storage reactions, providing a 40% performance boost. 


The researchers also placed the device in microfluidic channels, exposing it to blood vessel-like forces where flow and pressure fluctuate. Then, they used three devices linked together to power a tiny pH sensor that measures a blood vessels' pH levels and detects abnormalities that could point to a disease, such as tumor growth.


"It is extremely encouraging to see how new, extremely flexible, and adaptive microelectronics is making it into the miniaturized world of biological systems," says research group leader Prof. Dr. Oliver G. Schmidt.


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