Plastic Processors for Less Than a Penny Apiece

If you’ve been following statistics about the Internet of Things (IoT), which is growing by billions of devices every year, the numbers are pretty mind-boggling. But the truth is that expensive silicon chips are actually holding this rampant growth back

But now researchers have designed a new plastic processor, which they estimate will be able to be mass-produced for less than a penny. That’s right — the new Flexicore chips could kick-start a world in which everything — from bandages to bananas — could have a chip, according to a report by IEEE Spectrum.

The chip designs we currently use — even for the most basic microcontrollers — are too complex to be mass-produced in plastic: You surely won’t see a plastic processor on our list of best CPUs for gaming. This is the main issue these designs face, according to researchers at the University of Illinois Urbana-Champaign and flexible-electronics manufacturer PragmatIC Semiconductor — that existing chip designs are too complex for production on plastic with acceptable yields. 

Last year Arm and PragmatIC announced the development of the PlasticArm prototype, which implemented the Arm M0 processor design incorporating >56,000 semiconductor devices for a flexible and cheap microchip. This latest research suggests that a completely new architectural approach was needed to achieve usable yields and a sub-penny chip.

(Image credit: University of Illinois Urbana-Champaign)

To address the peculiarities of plastic chip design, the University of Illinois team built the new Flexicore processor design from scratch. Because yields dive when processor gate count rise, they decided to make a minimal design that reduced the gate count and used 4-bit and 8-bit logic instead of 16-bit or 32-bit alternatives. Flexicore memory architecture and its instruction set were optimized for fewer components and less complexity. The researchers also designed logic that re-uses parts (and so, has fewer transistors). Last but not least, the processor was designed so that it executes an instruction in a single clock cycle.

For chip manufacture, the research team used flexible thin-film semiconductor indium gallium zinc oxide (IGZO) technology. Readers will be familiar with IZGO for its use in monitor panel manufacturing. It is a reliable and established technology and films can be flexed into curves with a radius of millimeters with no ill-effects.

A sample 4-bit FlexiCore processor is 5.6mm square and contains 2,104 semiconductor devices, similar to a classic Intel 4004 CPU. Remember — earlier we mentioned the PlasticArm prototype using the Arm M0 architecture — the Flexicore uses less than 4% as many semiconductor devices. Manufacturing yields were over 80% and the researchers reckon a Flexicore chip would cost under a penny to produce. Yields with 8-bit designs weren’t good enough to break the one-penny barrier at this time.

There is still work to be done, and the researchers have already tried optimizing the Flexicore design for different processes and target workloads with some success. It will be interesting to read about how flexing chips affects performance and how durable these things are.

With this sub-penny plastic processor, and the move of flexible electronics from niche to mainstream, we may be seeing the dawn of truly ubiquitous electronics. The above research is going to be presented at the International Symposium on Computer Architecture later this month, so we should learn more about it and further development plans soon.