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This 3D printed door latch can be unlocked with a PIN code, yet doesn’t require electricity

Why it matters to you

3D-printed innovations like these may inspire the cheaper, simpler manufacturing of relatively complex devices.

You won’t find metamaterials in nature — in fact they may seem to defy its very laws. Consider the nanoscale wrinkles in wallpapers that can completely absorb sound. Or the light-bending particles that form the fabric of rudimentary invisibility cloaks. By experimenting with the shape, size, and arrangement of particles, engineers can create metamaterials that do seemingly impossible things.

Last September a team of researchers from Hasso Plattner Institute in Potsdam, Germany created 3D-printed objects with simple internal structures that could perform relatively complex functions. They called their door latches, pliers, and Jansen walkers “metamaterial mechanisms.”

“The field of metamaterials is an emerging and very interesting one,” Alexandra Ion, lead researcher and PhD student, told Digital Trends at the time. “Metamaterials can employ behavior that traditional materials cannot. We set out to explore this space and started by simply wondering if we can achieve, for example, rotation to implement a rotary knob.”

After developing a handle, Ion and her team realized that, by adding other cells through a custom metamaterial editing program that allows them to create rigid and shear blocks, they could attach a latch to their handle and create much more sophisticated systems.

This year they’ve added yet another feature: a PIN pad.

The PIN pad consists of a series of bistable springs, some of which are “locked” and other of which aren’t. By pressing the correct combination on the pad, the springs all switch to the unlocked position, allowing the handle and latch to turn.

“The goal of this work was to explore how we can create ‘materials that are machines’ at the same time,” Ion said of their metamaterial machines project.

Of course, these machines aren’t entirely practical. We certainly don’t recommend securing your home with them. Nonetheless, as Ion pointed out, the technology used to develop them could inspire cheaper and simpler manufacturing processes.

“These types of machines are very simple to fabricate, compared to the conventional manufacturing process of, for example, a door latch mechanism, which consists of many parts and requires assembly,” she said. “We envision that … doors can be 3D printed with the door latch mechanism already in place, in one single fabrication step.”