Researchers from the Lawrence Livermore National Laboratory (LLNL) are drawing inspiration from a mostly obsolete technology to drive 3D printing innovations forward. By 3D printing mechanical logic gates, like those used in original computers such as Charles Babbage’s Difference Engine, the researchers are demonstrating the potential of electronics-free, “sentient” materials.
Unlike today’s advanced computers, original computers were fully mechanical, using gears and levers to solve mathematical problems. Ever since the development of electronic circuits after WWII, however, mechanical computers have largely been left by the wayside. Until now.
A team from LLNL and researchers from the University of California, Los Angeles (UCLA) have drawn inspiration from the original computers and their building blocks to 3D print mechanical logic gates. These, the researchers say, could be used like LEGO to “build just about anything.”
In other words, the 3D printed logic gates could be embedded into a number of structured materials and programmed to react in certain ways, changing physical shape when exposed to certain environmental stimuli without the need for electricity or electronic circuits.
“Certain electric applications are limited, whereas with this system, the material could completely reconfigure itself,” explained lead researcher Andy Pascall. “If you embedded logic gates into material, that material could sense something about its environment. It’s a way of having a responsive material; we like to call it a ‘sentient’ material—that could have complicated responses to temperature, pressure, etc. The idea is it’s beyond being smart. It’s responding in a controlled, precise way.”
In terms of specific applications, the 3D printed logic gates could be used in space-bound rovers to help them stand up to challenging environments. For instance, if a rover on Venus got too hot, the sentient material could be programmed to open its pores to allow more coolant in. The material could also be used in low-power computers built to survive nuclear or electromagnetic pulse blasts and in robots used to collect information on nuclear reactors.
“The nice thing about our design is it’s not limited in scale,” Pascall added, reemphasizing that the material could be used in just about anything. “We can go down to an order of several microns up to as big as you need it to be, and it can be rapidly prototyped. This would be a difficult task without 3D printing.”
The 3D printed material relies on a specially designed flexure gate structure, designed by LLNL research engineer Robert Panas, assistant professor of mechanical aerospace and engineering at UCLA Jonathan Hopkins and summer student Adam Song. The flexures, which provide flexibility and movement to the material, function similarly to switches; they are chained together and when an environmental stimuli is applied, a “cascade of configurations” are triggered which perform mechanical logic calculations.
As the researchers explain, the gates work because of displacement and use an external binary signal from a transducer to perform a logical calculation. When the signal—such as a pressure pulse or pulse of light—is applied, the reaction translates into movement, creating a domino effect throughout the logic gates that changes the shape of the printed part.
“Many mechanical logic designs have substantial limitations and you run into fanciful designs that could not be fabricated,” Panas said. “What we’re doing is using these flexures, these flexible elements that are 3D printed, which changes how the logic structure can go together. We eventually realized we needed a displacement logic setup (to transfer information). Surprisingly, it actually worked.”
The action achieved by the triggered flexures enables the structure to be preprogrammed or to store information without any external energy. This makes them well suited for challenging environments, such as those with high radiation, temperature or pressures. The 3D printed logic gates could therefore be used to collect temperature readings in vaccines or foods, or be integrated into bridges to collect structural loading data.
The 3D printed logic gates were printed at LLNL using a two-photon stereolithography process. “Once the structure was printed, we then deformed it in place using different lasers that act as optical tweezers,” Hopkins added. “We then actuated the switches using those optical tweezers as well. It’s a revolutionary new approach for making these materials at the micro-scale.”
Excitingly, the researchers plan to make their design plans open source in the near future. A study detailing the research was recently published in the journal Nature Communications.