Stretchable hologram displaying multiple images

Stretchy holograms can switch between images

Image credit: American Chemical Society

Researchers at the University of Pennsylvania have found a method for projecting holograms that switch between different images as the materials used to generate them are stretched.

While a photograph records an image with a lens, a hologram is a recording of a light field. As they contain data about the light flowing in every direction within a certain space, they can be used to display 3D images.

Star Wars-style video holograms are still a long way away from replacing Skype as an everyday mode of communication, but thanks to research carried out at the University of Pennsylvania, a new technique for creating shifting holograms brings them closer to reality.

Professor Ritesh Agarwal and his team, based at the university’s department of materials science and engineering, created these moving holograms using metasurfaces.

Metasurfaces are ultra-thin, nanostructured surfaces which can be designed with an almost unlimited range of properties, including the ability to project holograms. They have been used by scientists in previous studies to create striking 3D and multi-colour holograms.

The University of Pennsylvania researchers had already created their own metasurface by embedding gold nanorods in a stretchy silicone film of polydimethylsiloxane, and Professor Agarwal wanted to understand how stretching this surface would cause a holographic image to change.

Using computational simulations, the team calculated the extent to which a holographic image expands as the material being used to generate it is stretched, and how far the image plane moves from its starting position.

Based on these models and experiments, they created computer-generated holograms composed of two to three images.

As their metasurface was stretched, they found that one image appears after another. They demonstrated this by creating a pentagon hologram in the material’s relaxed state. This was replaced with a square as the material was stretched, then a triangle. As the material was stretched, the image also became larger.

According to the researchers, who report their findings in the latest issue of Nano Letters, the technology could have applications in virtual reality, reconfigurable optical communications and flat displays.

3D holograms are beginning to be used to simulate the presence of a public figure at an event, such as in concerts and during the run-up the the French presidential election.

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