In previous articles, we explored the realm of smart textiles and their distance from achieving the elusive invisibility cloak seen in Harry Potter and fictional characters such as the Predator alien. However, a recent development suggests that a Chinese scientist may have brought us closer to J.K. Rowling’s fantastical fabric. The inventor asserts that, someday, an invisibility cloak could become a fashionable wardrobe accessory for everyone. How was this breakthrough achieved?
How an invisibility cloak works
The fundamental principle behind an invisibility cloak is to manipulate light rays, directing them in a manner that reaches objects positioned behind the cloak. Essentially, the aim is to bend light, as conventional reactions involve either light absorption, obscuring the background, or light reflection, illuminating and revealing the object. Three primary approaches are explored for achieving invisibility:
- Metamaterials: A theoretical method involves using metamaterials—materials intentionally designed with electromagnetic properties that are not naturally occurring. These materials can bend or deflect light around an object, rendering it invisible to the naked eye.
- Optical Manipulation: Other research delves into manipulating light using lenses or optical devices to bend it around an object, effectively rendering it invisible.
- Camouflage Techniques: A third option utilizes cameras and projectors to create the illusion of invisibility. Cameras capture an image, and projectors reproduce it from the other side, creating the appearance of transparency.
Donghua University invisibility cloak
At a recent scientific conference in Shanghai, Professor Chu Junhao from Donghua University unveiled what appears to be the most realistic invisibility cloak to date. During the demonstration, he described it as a sheet featuring multiple rows of cylindrical convex lenses. Each lens can compress objects parallel to it, causing light refraction. Consequently, the image is fragmented into millions of identical particles, rendering them indistinguishable to the human eye. Junhao asserts that this technology is poised to “change our lives.”
To witness the technology in action, you can check out a video uploaded to X that showcases its capabilities. Initially, the researcher’s legs are visible through the panel but become blurred. When two individuals turn him, the researcher and his captors vanish, revealing the scene’s background.
Magic! Chu Junhao, academician of the Chinese Academy of Sciences, demonstrated “invisibility”. pic.twitter.com/qNESHCVvPK
— Zhang Heqing (@zhang_heqing) October 30, 2023
A brief history of invisibility in ten milestones
Invisibility technologies, though prominent in books and fiction like H.G. Wells’ “The Invisible Man,” the Star Trek series, and previously mentioned examples, have been subjects of scientific exploration for decades. While not as striking as the developments by Donghua University’s team, recent years have witnessed crucial milestones in advancing invisibility cloaks. Here are some significant moments:
- 2006: Duke University researchers in the USA reveal the first cloak, albeit limited to two dimensions and functioning solely with microwaves.
- 2007: The British Army experiments with an “invisible” tank employing a blend of cameras and projectors to create a fictitious image, concealing the vehicle.
- 2008: The University of California conducts initial trials with metamaterials, altering the direction of visible and infrared light to achieve invisibility effects.
- 2010: Nature reports two scientists working on a metamaterial derived from calcite crystals that could enable cost-effective invisibility.
- 2011: The University of Texas demonstrates advancements in invisibility using carbon nanotubes.
- 2012: Duke University achieves another breakthrough: its invisibility system can completely obscure objects as small as a few centimeters.
- 2013: The University of Texas refines its invisibility technology, achieving effectiveness with a material only 0.15 mm thick.
- 2014: The University of Rochester successfully renders small objects of a few centimeters invisible, irrespective of the observer’s position.
- 2015: A U.S. National Science Foundation scientist wins the Waterman Award for crafting metamaterials capable of masking three-dimensional objects.
- 2019: A Canadian company specializing in camouflage clothing unveils Quantum Stealth, a paper-thin material utilizing lenticular lenses capable of concealing soldiers and vehicles.
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