Feb 23, 2017 | By Benedict

A group of researchers from the Hasso Plattner Institute in Germany has devised a technique for 3D printing "digital mechanical metamaterials" that can be used to create complex devices such as combination locks. The metamaterials contain special spring-loaded cells that can trigger signals.

Back in September, we reported on the work of a group of researchers at the Hasso Plattner Institute in Potsdam, Germany, who had developed an incredible 3D printing technique for creating mechanical structures. Their research involved 3D printing single-part structures consisting of hundreds of unique “cells” that would deform in precise ways when pressurized, allowing the entire printed structure to behave like a multi-part mechanical device. One example of their work was a door handle and latch system made of a flexible plastic; when the handle of the system was twisted, the flexible cells would deform in a way that moved the latch inwards, opening the door.

Four of the nine researchers on that project have now returned with a new research paper that adds an entirely new element to the amazing 3D printable metamaterials first demonstrated last year. Specifically, the researchers have introduced a new type of cell that can send a digital mechanical signal using an embedded bistable spring. When triggered, this embedded spring discharges, with the resulting impulse triggering one or more neighboring cells, resulting in signal propagation. This means that 3D printed devices made with the special metamaterials can now incorporate “simple logic functions” in addition to basic mechanics. Or, in practice: that clever handle and latch system made last year can now be locked and unlocked with a combination code.

The cornerstone of this new research is the so-called bit cell incorporated into the 3D printed metamaterial structures. These bit cells, carefully engineered by the Hasso Plattner researchers, each contain a bistable spring, which allows them to take on two discrete states: tense, prior to being triggered; and relaxed, after being triggered. Each of these cells has an input and output port, allowing it to receive and pass on the trigger signal. Arranging a number of these bit cells in a line therefore allows the researchers to create a signal propagation mechanism.

The researchers have demonstrated the huge potential of this technology with a combination lock, turning the handle and latch system of the previous project into a piece of advanced machinery. To do so, the researchers created a complex system of 82 bit cells that can evaluate an inputted combination, triggering the unlocking mechanism if the code is correct or preventing the door from opening if incorrect. “To implement logic functions, we need to go beyond merely transmitting signals to also evaluating signals, which we achieve by blocking them,” the researchers explain. “In the combination lock, we block signals for wrong digit inputs so that the door stays blocked.”

These new digital mechanical metamaterials aren’t just for 3D printed locks, either. As with the project from last year, the Hasso Plattner researchers have developed a custom voxel-style editing software that can be used to model 3D printed mechanical structures with precisely controllable cells, including spring-loaded bit cells. All the hard work is taken care of by the software: users can simply input various logical functions, which can then be converted into precise 3D printable cell arrangements that implement that function.

In the first video below, which was uploaded last week by the Hasso Plattner Institute, the researchers demonstrate how the digital mechanical metamaterials are used in the 3D printed combination lock. The second video shows the deforming metamaterial mechanisms from the original 2016 project.

The four authors of the 2017 research paper “Digital Mechanical Metamaterials” were Alexandra Ion, Ludwig Wall, Robert Kovacs, and Patrick Baudisch.

 

 

Posted in 3D Printing Materials

 

 

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