Disposable battery melts in your body

Consisting of metal foil, saline, and biodegradable polymers, the new device simply dissolves in the body, after delivering drugs or wirelessly relaying vital measurements.
Written by Janet Fang, Contributor


biodegradable battery made with metal foil.jpg

Biodegradable electronics endow temporary implants with advanced semiconductor functionality. After they’ve served their purpose, they’re simply reabsorbed by the body. 

We’ve been hearing about biodegradable electronics for a while now: from edible batteries powered by cuttlefish ink to paper-thin, flexible supercapacitors. But this time, researchers may actually be on their way towards a truly useful one. For starters, this new battery has a relatively higher current and power density and can last for a day. 

Nature reports
In 2012, materials scientist John Rogers at the University of Illinois at Urbana-Champaign unveiled a range of biodegradable silicon chips that could monitor temperature or mechanical strain, radio the results to external devices, and even heat up tissue to prevent infection. Some of those chips relied on induction coils to draw wireless power from an external source. But wireless power transfer is problematic for devices that need to go deep within tissue or under bone. 

And the components that receive the power are pretty complicated, which adds to the bulk. So to provide a tidier solution, Rogers and colleagues created a fully biodegradable battery that uses metal foils, saline solution, and biodegradable polymers. “Almost all of the key building blocks are now available” to produce self-powered, biodegradable implants, Rogers tells Nature.

The device, Nature explains, consists of anodes of magnesium foil and cathodes of iron, molybdenum or tungsten -- metals with ions that are biocompatible at low concentrations. The electrolyte between the two electrodes is a phosphate-buffered saline solution, and the whole system is packaged in polyanhydride, a biodegradable polymer. 

Currents and voltages vary depending on the metal, but at least one version produces a steady 2.4 milliamps of current. A tiny battery with a surface area of 0.25 square centimeters and a thickness of 1 micrometer could realistically power a wireless sensor for up to a day (but not much longer). 

The implant dissolves completely (pictured above) in three weeks -- but not before dispensing drugs or monitoring vital signs, and then wirelessly relaying data. Once dissolved, the battery releases less than 9 milligrams of magnesium, a concentration that’s unlikely to cause problems in the body, according to Rogers. 

The device was described in Advanced Materials last week. 

[Via Nature]

Image: L. Yin et al., “Materials, Designs, and Operational Characteristics for Fully Biodegradable Primary Batteries,” Advanced Materials 2014

This post was originally published on Smartplanet.com

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