While we’re currently witnessing the rise of tiny electronic devices such as biosensors, many of those devices do have one limiting factor – they still require not-so-tiny batteries, which ends up somewhat defeating the whole miniaturization process. Although some devices can get their power from external sources, scientists from Harvard University and the University of Illinois at Urbana-Champaign have come up with an alternative ... functional 3D-printed lithium-ion batteries no larger than a grain of sand.

The batteries' anodes and electrodes are made from two types of electrochemically active ink, which are extruded through a printer nozzle that’s narrower than a human hair. The ink used to create the anodes contains nanoparticles of one lithium metal oxide compound, while nanoparticles of another such compound are present in the ink used in the cathodes.

Both components are built up by depositing successive layers of the quick-hardening ink onto a comb-shaped surface. The resulting anode and cathode end up face-to-face, their electrodes (the teeth of the two combs) interlaced with one another. That assembly is then encapsulated within a tiny case, an electrolyte solution is added, and a working microbattery is the result.

The printing process (left) and the finished encapsulated battery

After testing how much power the batteries could store and deliver, along with the amount of time that they could hold a charge, it was determined that “The electrochemical performance is comparable to commercial batteries in terms of charge and discharge rate, cycle life and energy densities.” Thin film batteries have previously been used to power some tiny devices, although their performance is reportedly not nearly as good.

The research was led by Harvard’s Prof. Jennifer Lewis. A paper on the batteries was recently published in the journal Advanced Materials.

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