System Bits: Oct. 1

Origami-shaped antennas, bendable ceramics with a memory for shape.


Origami-Shaped Antennas
A Georgia Tech-led research team is working to develop a unique approach to making extremely compact and highly efficient antennas and electronics based on principles derived from origami paper-folding techniques to create complex structures that can reconfigure themselves by unfolding, moving and even twisting in response to incoming electromagnetic signals.

The structures could be made from a number of different materials, such as paper, plastics and ceramics. Sophisticated inkjet printing techniques would deposit conductive materials such as copper or silver onto the antenna elements to provide signal receiving and other capabilities.

Further, several potential activation mechanisms would allow the origami-shaped antennas to rapidly unfold in response to various incoming signals including the harvesting of ambient electromagnetic energy in the air, and the use of chemicals that produce movement in ways that mimic nature.

The result will be powerful, ultra-broadband capabilities in a diminutive antenna measuring only a couple of centimeters when folded. Commercial and military applications for such antennas could include many types of communications equipment, as well as wireless sensors, smart skin — sensors for structural health monitoring, portable medical equipment, electronics mounted on vehicles or flying/space platforms, agricultural sensors, and cognitive electronics that adjust to ambient conditions in real time.

Ceramics that bend without breaking
Ceramics are not known for their flexibility as they tend to crack under stress but researchers from MIT and Singapore said they’ve found a way around that problem; for very tiny objects, at least. The team has developed a way of making minuscule ceramic objects that are not only flexible, but also have a memory for shape. When bent and then heated, they return to their original shapes.

Shape-memory metals and some polymers, which can bend and then snap back to their original configurations in response to a temperature change, have been known since the 1950s, but not in ceramics.

In principle, the molecular structure of ceramics should make shape memory possible, the researchers said, but the materials’ brittleness and propensity for cracking has been a hurdle. The key to shape-memory ceramics, it turns out, was thinking small.

The researchers accomplished this in two ways. First, they created tiny ceramic objects, invisible to the naked eye. Then, they concentrated on making the individual crystal grains span the entire small-scale structure, removing the crystal-grain boundaries where cracks are most likely to occur.

Those tactics resulted in tiny samples of ceramic material — samples with deformability equivalent to about 7% of their size, whereas most things can only deform about 1%. Normal ceramics can’t even bend that much without cracking.

While a micrometer is pretty tiny by most standards, it’s actually not so small in the world of nanotechnology. As such, these materials could be important tools for those developing micro- and nanodevices, such as for biomedical applications.

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