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How to Brew Your Own Conductive Ink

Draw working circuits in pen and ink

4 min read
Photo of someone soldering.
Photo: W. Wayt Gibbs

I’m not ashamed to admit it—my soldering skills stink. That puts a real crimp in my ability to prototype circuit ideas. Breadboards work, but by design, they significantly constrain how you can arrange components.

So I was excited when I spotted a preprint article on ArXiv.org describing a new liquid-metal ink. Conductive inks made from silver nanoparticles have been available for some time; recently, a group at Georgia Tech demonstrated a way to use them in inkjet printers to create custom circuits. But they are quite pricey, and I’m not keen on the idea of pumping metal through my printer. In contrast, this new ink can be used in an ordinary roller-ball pen to draw circuit traces, and the recipe for making the ink is amazingly straightforward: Mix 75.5 parts gallium with 24.5 parts indium in a beaker of deionized water, heat to 50 °C, stir, and voilá: an alloy that’s liquid at room temperature, costs about US $1 per milliliter, and is two orders of magnitude more conductive than the nanoparticle inks; its resistivity is just 17 times that of copper. This I had to try.

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From WinZips to Cat GIFs, Jacob Ziv’s Algorithms Have Powered Decades of Compression

The lossless-compression pioneer received the 2021 IEEE Medal of Honor

11 min read
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Photo of Jacob Ziv
Photo: Rami Shlush
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Lossless data compression seems a bit like a magic trick. Its cousin, lossy compression, is easier to comprehend. Lossy algorithms are used to get music into the popular MP3 format and turn a digital image into a standard JPEG file. They do this by selectively removing bits, taking what scientists know about the way we see and hear to determine which bits we'd least miss. But no one can make the case that the resulting file is a perfect replica of the original.

Not so with lossless data compression. Bits do disappear, making the data file dramatically smaller and thus easier to store and transmit. The important difference is that the bits reappear on command. It's as if the bits are rabbits in a magician's act, disappearing and then reappearing from inside a hat at the wave of a wand.

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