3D printed objects interact with WiFi sans electronics

In this backscatter system an antenna embedded in a 3D printed object reflects the radio signals emitted by a regular WiFi router.
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University of Washington engineers have developed 3D printed plastic objects that are able to connect to WiFi – without electronics.

University of Washington engineers have developed 3D printed plastic objects that are able to connect to WiFi – without electronics.

The team of engineers are making CAD models that will be accessible to the public. 3D-printing enthusiasts will be able to use these models to create objects out of commercially available plastics that are able to wirelessly communicate with other smart devices. These include an attachment for a laundry soap bottle that will sense when the soap is running low, and automatically order more.

Other objects include a battery-free slider that controls music volume, a button that automatically orders more cornflakes from an online store, or a water sensor that sense an alarm to a phone when it detects a leak.

“Our goal was to create something that just comes out of your 3D printer at home and can send useful information to other devices,” said co-lead author and UW electrical engineering doctoral student Vikram Iyer.

But to do this, the researchers had to figure out how it is possible for objects using only plastic to communicate wirelessly with WiFi.

The team employed backscatter techniques that allow devices to exchange information. They replaced some functions normally performed by electrical components with mechanical motion activated by springs, gears, switches and other parts that can be 3D printed.

In this backscatter system, an antenna embedded in a 3D printed object reflects the radio signals emitted by a regular WiFi router. The information embedded in those reflected patterns can then be “read” by the WiFi receiver in a phone, computer or other device.

In this case, the antenna is contained in a 3D printed object made of 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. The use of gears of different speeds allow the encoding of digital data, with binary data indicated 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.

For example, a 3D printed attachment on a laundry liquid bottle includes gears which turn when soap flows out of the bottle. The speed of the gears turning indicate the amount of soap flowing out, and the 3D printed switch in the attachment works to wirelessly transmit the data. The receiver then tracks the amount of detergent used, calculates the amount left, and when it dips below a fixed amount, sends a message to order more.

The team also 3D printed plastic scroll wheels, sliders and buttons that can wirelessly interact with computers, phones and other WiFi-connected devices, and demonstrated how to use the magnetic properties of some 3D printed materials to invisibly encode static data in the objects above, which could be useful for inventory tracking or to help robots interact with them.