A MetaSense joystick

3D-Printing Complex Sensors And Controls With Metamaterials

If you’ve got a mechatronic project in mind, a 3D printer can be a big help. Gears, levers, adapters, enclosures — if you can dream it up, a 3D printer can probably churn out a useful part for you. But what about more complicated parts, like sensors and user-input devices? Surely you’ll always be stuck buying stuff like that from a commercial supplier. Right?

Maybe not, if a new 3D-printed metamaterial method out of MIT gets any traction. The project is called “MetaSense” and seeks to make 3D-printed compliant structures that have built-in elements to sense their deformation. According to [Cedric Honnet], MetaSense structures are based on a grid of shear cells, printed from flexible filament. Some of the shear cells are simply structural, but some have opposing walls printed from a conductive filament material. These form a capacitor whose value changes as the distance between the plates and their orientation to each other change when the structure is deformed.

The video below shows some simple examples of monolithic MetaSense structures, like switches, accelerometers, and even a complete joystick, all printed with a multimaterial printer. Designing these structures is made easier by software that the MetaSense team developed which models the deformation of a structure and automatically selects the best location for conductive cells to be added. The full documentation for the project has some interesting future directions, including monolithic printed actuators.

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Optical Microscope Resolves Down To 40 Nanometers

Optical microscopes depend on light, of course, but they are also limited by that same light. Typically, anything under 200 nanometers just blurs together because of the wavelength of the light being used to observe it. However, engineers at the University of California San Diego have published their results using a hyperbolic metamaterial composed of silver and silica to drive optical microscopy down to below 40 nanometers. You can find the original paper online, also.

The technique also requires image processing. Light passing through the metamaterial breaks into speckles that produce low-resolution images that can combine to form high-resolution images. This so-called structured illumination technique isn’t exactly new, but previous techniques allowed about 100-nanometer resolution, much less than what the researchers were able to find using this material.

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Swiss Cheese Metamaterial Is An Analog Computer

If you have had trouble with ordinary calculus, you may not be pleased to hear about “photonic calculus” — a recent idea from [Nader Engheta] of the University of Pennsylvania. The idea is that materials with certain properties could manipulate an electromagnetic wave in a way to solve a specific mathematical equation. [Engheta] proposed this idea back in 2014 and recently announced that he and his team have a demonstration device that proves the concept. The analog computer is about twice the size of an airplane’s tray table and made of CNC-shaped polystyrene. It solves Fredholm integral equations of the second kind.

The analog computer uses microwaves for the input and the polystyrene acts as a dielectric full of air holes. The team likens its structure to that of Swiss cheese. The shape is generated through an inverse design process which builds the shapes from known solutions to the equations. That means a particular set of shapes will do one specific equation. The equation could, for example, model the sound volume in a concert hall. You can encode certain parameters in the input wave and the output would specify the volume at different locations. However, a change to the actual equation would require a new set of plastic pieces.

The computation is very fast. Using microwaves, the answer comes out in a few hundred nanoseconds — a speed a conventional computer could not readily match. The team hopes to scale the system to use light which will speed the computation into the picosecond range. Creating a new optical analog computer could be similar to how we burn a CD or DVD today.

Analog computers predate digital ones by a lot. We really want to build one like [Bill Schweber’s]. Then again, we wouldn’t mind finding a Donner 3500 at a hamfest, either.

3D Printed Key-Code Is Plastic Digital Logic

3D printers are great for creating static objects, but if you’re clever, it’s possible to print functional devices. If you’re absolutely brilliant you can go far beyond that, which is the case here. This door handle with a key-code lock does it all with 3D printing using mechanism designs that look like alien technology. This is just one application of a much more interesting mechanical digital logic they’re developing (PDF).

Working from the [Hasso-Plattner-Institut], the research team is focusing on metamaterials as mechanisms in and of themselves. The crux of this lock is a series of bistable springs that — if the correct code is entered — will trigger in series to unlock the door. The project builds on the grid of shearing cells seen in the door handle we featured last year. It happens quickly in the video, but the intricate cascade of the handle unlocking is a treat to witness.

It’s a fascinating show of mechanical design. The common elements of digital electronics are all present: set or unset bits, logic gates, propagation issues, the whole works. But there are added challenges in this system, like the need for special cells that can turn the logic chain by 90 degrees and split the signal into more than one part.

This signal splitting is seen in the upper right (bifurcation) and leads into what is in effect an amplifier. The locking bolt must be moved twice the distance of a normal cell, so a dual-cell input is necessary to offset the loss of force from the incoming smaller cells. Cognitively we understand this, but we’re still trying to gain an intuitive sense of the amplifer mechanism.

One thing’s for sure, the overall concept is far cooler than this admittedly awesome door lock mechanism. The paper is worth your time for a deep dive. It mentions their design editor software. You can play with it online but we don’t think it’s been updated to include the new logic cells yet.

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