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Fig. 1 Julie Russell/LLNL
Lawrence Livermore National Laboratory scientists and engineers combed mechanical computing with 3D printing to create “sentient” materials that respond to changes in their surroundings, even in extreme environments. Pictured, from left, are LLNL researchers Julie Jackson Mancini, Logan Bekker, Andy Pascall, and Robert Panas.

Researchers 3D Print Mechanical Logic Gates

The gates could be useful in rovers sent to hostile environments such as Venus, as well as in low-power computers intended to survive nuclear or electromagnetic pulse blasts.

Engineers and scientists from the Lawrence Livermore National Laboratory and the University of California, Los Angeles are 3D printing mechanical logic gates, the basic building blocks of computers that can performing any kind of math calculations.
These 3D-printed logic gates could be used to build just about anything, researchers said, embedded into any type of architected material and programmed to react to its environment by physically changing shape without the need for electricity. This would make them useful in areas of high radiation, heat, or pressure.

“If you embedded logic gates into material, that material could sense something about its environment,” says lead researcher Andy Pascall. “It’s a way of having a responsive material—we like to call it a sentient material—that could have complicated responses to temperature and pressure.”

Mechanical logic gates, while are not as powerful as typical computers, could prove useful in rovers sent to hostile environments such as Venus, or else in low-power computers intended to survive nuclear or electromagnetic pulse blasts that would destroy electronic devices, researchers said.

A series of mechanical logic gates are 3D printed using the Large Area Projection Microstereolithography (LAPµSL) method.

In a Venusian rover, Pascall said scientists could build controls so if the rover got too hot, the material could open its pores to let in more coolant without the need for electricity. The devices also could be used in robots sent that explore damaged nuclear reactors (e.g., Fukushima).

“The design is not limited in scale,” Pascall says. “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 device has built-in flexure gates that let the part bend and move. The flexures also act switches. They are chained together and, when stimulated, trigger a cascade of configurations that can be used to perform mechanical logic calculations without external power.

The gates work using displacement, taking in an external binary signal from a transducer (such as a pressure pulse or pulse of light from a fiber optic cable) and performing a logical calculation. The result is translated to movement, creating a domino effect throughout all the gates that physically changes the shape of the device.

The flexures’ buckling action lets the structure to preprogrammed or store information with no need for an auxiliary energy flow, Panas says, making them well-suited for environments with high radiation, temperature, or pressures. The logic gates could collect temperature readings in vaccines or foods and notify when certain thresholds have been reached

“We see this as simple logic being put into high-volume materials, potentially getting readings in places where you can’t normally get data,” Panas says.

The sub-micron gates were made using a 3D printing process called two-photon stereolithography. It has a laser that scans within a photocurable liquid polymer and cures and hardens where the laser shines.

The printed structure was deformed using different lasers that act as optical tweezers. These lasers were also used to actuate the switches.

The design was driven by computationally modeling the gates’ buckling behavior, and although they were designed in two dimensions, Pascall said he would like to move to 3D. Pascall hopes the technology can be used to design secure, personalized control systems, and said plans are to release the design as open-source. The technology also could be a teaching tool for students who could print logic gates using commercial 3D printers and learn how computers work, he added.

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