Design Con 2015

3D microbatteries: A future option for ultralow-power applications?

-August 14, 2013

Even those tiny micropower circuits need a source of power, and that source is a distinct, discrete component, of course - and often physically larger than the circuit it supplies. While energy harvesting may be a viable way to get the needed power, in many cases it may be unavailable, impractical, or too inefficient.

That's where additive manufacturing (AM) - also called 3D manufacturing or rapid prototyping (RP) - may offer a solution. I recently saw a short news item ("Additive Manufacturing Produces Microbatteries"), along with an informative photo and video, summarizing a recent journal paper that discussed how researchers fabricated a pinhead-size Li-ion battery using AM techniques (see "3D Printing of Interdigitated Li-Ion Microbattery Architectures" and its supporting information (PDF) for more details, and check out Figure S4 in the latter). While such a battery can not store much energy, it might be enough for some applications, particularly use-once, one-shot, or short-term ones.

I know that AM and RP are getting a lot of attention lately. It's a pretty amazing combination of materials, machines, software, and techniques that allow you build, from the ground up (so to speak) small and mid-size parts using a variety of materials, including various plastic resins, sintered powered metal, and even starch-based composites.

I've seen some AM machines in action, building small parts right in front of you, driven by a CAD program. Some of the AM machines use lasers to cure the raw material as it rises on a platform; some use a variation on the mass-market ink-jet printer technology to precisely squirt the raw material.

I have even seen videos of "inkjet" AM being used with cultured human tissue cells in an experimental program to recreate the ear of an accident victim. It's all pretty amazing stuff, no doubt about that. (The change in mindset and associated production implications of RP are analogous to those amazing machines from vendors such as LPKF Laser & Electronics, which precisely fabricate a non-etched "printed circuit" board using CNC routers and lasers, and they do it right in front of you, driven by your layout file.)

In some ways, though, I wonder and worry if AM/RP is perhaps getting too much attention and buzz. Since so many investors and others are looking for the "next big thing," there's somewhat of an echo chamber that amplifies whatever legitimate attention an emerging technology is getting. Next thing you know, the technology is being touted and hyped as the answer to all your problems, whatever that problem is. It was only a few years ago that "3D video" or "stereo TV" was the next big thing, and we know how that worked out.

Still, there's no denying that AM is very real, can solve lots of problems, and opens up new ways of addressing both existing and new manufacturing objectives. It's especially nice for short or custom production runs, since it takes the need for costly, formal tooling out of the equation.

Looking at the AM-produced experimental battery, I can't help but wonder if someday we'll be "fabricating" a small power cell right on the IC die itself, as one of the final production steps. Then the entire circuit plus its power source could be encapsulated and be ready to use, perhaps with a few external leads of I/O if needed.

If you are interested in following developments in AM and RP, there are lots of good information sources out there. I look at Desktop Engineering since it covers both what's coming very soon as well as what you can do right now. It also has interesting, "how they did it" product-design examples done using RP machines and materials, along with the CAD/CAM programs that drive them. Also keep an eye on Wiley's Advanced Materials for some insight into basic advances in material science, which are the foundation of much of our technological progress.

Have you been following AM/RP? If so, where and how do you think it may help your next design, or change your product-design approach?

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