3D printed objects use backscatter to communicate using Wi-Fi

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University of Washington researchers claim to have created 3D plastic objects and sensors that can not only collect useful data, but also communicate with other WiFi-connected devices.

According to the team, using CAD models being made available to the public, anyone will be able to create objects using commercially available plastics that can communicate wirelessly with other smart devices. Examples suggested by the team include a battery-free slider that controls music volume and a water sensor that sends an alarm when it detects a leak.

“Our goal was to create something that just comes out of a 3D printer at home and can send useful information to other devices,” said electrical engineering doctoral student Vikram Iyer. “But the big challenge is how do you communicate wirelessly with WiFi using only plastic? That’s something that no one has been able to do before.”

To produce such objects, the team employed backscatter techniques that allow devices to exchange information. In this instance, some functions normally performed by electrical components were replaced with mechanical motion activated by springs, gears, switches and other parts that can be 3D printed.

Backscatter systems use an antenna to transmit data by reflecting radio signals emitted by a WiFi router or other device. Information embedded in those reflected patterns can be decoded by a WiFi receiver. In this case, the antenna in the 3D printed object is made of a conductive printing filament that mixes plastic with copper.

Physical motion triggers gears and springs elsewhere in the 3D printed object that cause a conductive switch to intermittently connect or disconnect with the antenna and change its reflective state. Information is encoded by the presence or absence of the tooth on a gear. Energy from a coiled spring drives the gear system and the width and pattern of gear teeth control how long the backscatter switch makes contact with the antenna, creating patterns of reflected signals that can be decoded by a WiFi receiver.

The researchers 3D printed several different tools that could sense and send information successfully to other connected devices – a wind meter, a water flow meter and a scale. They also 3D printed WiFi input ‘widgets’, such as buttons, knobs and sliders that can be customised to communicate with other smart devices.

By using a 3D printing filament that combined plastic with iron, the team also took advantage of magnetic properties to encode static information in 3D printed objects – which, according to the team, could range from barcode identification for inventory purposes or information about the object that tells a robot how to interact with it.