Nanostructure-based touchless display responds to the sweat on the user’s finger

Nanostructure-Based Touchless Display Responds To Sweat-1

The age of touchscreens is nearing its end. At present, scientists are working to create innovative touchless displays which, while still relying on the ubiquitous finger-swipe, can operate without any actual contact. These touchless positioning interfaces (TPI), currently being developed by researchers at LMU Munish and Stuttgart’s Max Planck Institute for Solid State Research, are made up of specially-engineered nanostructures that are capable of changing their optical and electrical properties, every time the user’s finger comes near it.

Recently published in the Advanced Materials journal, the research aims at eliminating the common drawbacks of currently-available touchscreen controls, such as mechanical wear associated with prolonged use, and the risk of transmission of bacteria and viruses. Instead, the new technology uses an innovative approach, centered on our body sweat, to comprehend the user’s input, without needing any kind of physical contact. Basically a special type of humidity sensor, the contraption reacts to the perspiration of an incoming finger, converting it into a measurable electrical signal or a color change of the constitutive material.

The sensor is made up of nanostructures, which in turn contain a chemical substance called phosphatoantimonic acid. Comprised of phosphorous, antimony, oxygen and hydrogen atoms, this acid is known for its ability to absorb water and swell up. The increased moisture brings about a major change in the material’s physical properties. For instance, a rise in the stored water level actually causes its electrical conductivity to increase significantly. Since it exists as a crystalline solid at room temperatures, it could one day be used to create highly-interactive touchless interfaces. Speaking about the project, Pirmin Ganter, of the Max Planck Institute, said:

Because these sensors react in a very local manner to any increase in moisture, it is quite conceivable that this sort of material with moisture-dependent properties could also be used for touchless displays and monitors.

To further develop the technology, the researchers have built a photonic nanostructure, using microscopic sheets of the acid, which changes color upon exposure to moisture. In case of touchless displays, this distinct change in color would inform the user that his or her input has been successfully recognized and processed by the screen. To create a prototype of such a screen, the scientists sandwiched alternating layers of phosphatoantimonate nanosheets and titanium dioxide or silicon dioxide nanoparticles, into a thickness of around one millionth of a meter. The team explained:

The color of the nanostructure turns from blue to red when a finger gets near, for example. In this way, the color can be tuned through the whole of the visible spectrum depending on the amount of water vapor taken up… The reason for this lies in the storage of water molecules between the phosphatoantimonate layers, which makes the layers swell considerably. A change in the thickness of the layers in this process is accompanied by a change in the color of the sensor – produced in a similar way to what gives color to a butterfly wing or in mother-of-pearl.

One of the chief features, of the technology, is its swift reactivity. Unlike other touchless interfaces that often take up to few seconds to respond, the new contraption can react to even the slightest humidity changes in mere milliseconds. For it to replace today’s touchscreen displays, however, the technology would have to be optimized for mass production. At present, the scientists are trying to develop a special protective coating that would reduce mechanical wear, without effecting the material’s sensitivity. Researcher Bettina Lotsch added:

Ultimately, we could see touchless displays also being deployed in many places where people currently have to touch monitors to navigate.

Source: Max Planck Society / Advanced Materials

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