3-D printed plastic sensors connect to Wi-Fi
The researchers’ goal was to be able to 3D print wireless sensors, input widgets, and objects that can communicate with smartphones and other Wi-Fi devices without the need for batteries or electronics. With that in mind, they developed a toolkit for wireless connectivity that can be integrated with 3D digital models and fabricated using commercially available desktop 3D printers and plastic filament materials.
“Our goal was to create something that just comes out of your 3-D printer at home and can send useful information to other devices,” says Vikram Iyer, co-lead author of a paper on the project and UW electrical engineering doctoral student. “But the big challenge is how do you communicate wirelessly with Wi-Fi using only plastic? That’s something that no one has been able to do before.”
The 3D printed objects are made of conductive printing filament that mixes plastic with copper. To enable them to communicate, the researchers used backscatter techniques, whereby an antenna embedded in the objects reflects radio signals emitted by a Wi-Fi router to encode information that is able to be then “read” by the Wi-Fi receiver in a receiving device, such as a phone or computer.
Functions normally performed by electronic components were replaced by mechanical motion activated by springs, gears, switches, and other parts that can be 3-D printed. Physical motion — such as pushing a button, liquid flowing out of a bottle, turning a knob, or removing an item from a weighted tool bench — triggers gears and springs elsewhere in the 3-D printed object, causing a conductive switch to intermittently connect or disconnect with the antenna and change its reflective state.
The shape of the gears and the speed at which they move control how long the backscatter switch makes contact with the antenna, creating patterns of reflected signals that can be decoded by a Wi-Fi receiver.
“As you pour detergent out of a Tide bottle, for instance, the speed at which the gears are turning tells you how much soap is flowing out. The interaction between the 3-D printed switch and antenna wirelessly transmits that data,” says the paper’s senior author Shyam Gollakota, an associate professor in the Paul G. Allen School of Computer Science & Engineering. “Then the receiver can track how much detergent you have left and when it dips below a certain amount, it can automatically send a message to your Amazon app to order more.”
The researchers 3-D printed several different tools that were able to sense and send information successfully to other connected devices, including a wind meter, a water flow meter, and a scale. They also 3-D printed Wi-Fi input widgets such as buttons, knobs, and sliders that can be customized to communicate with other smart devices in the home and enable an ecosystem of “talking objects” that can seamlessly sense and interact with their surroundings.
The researchers also experimented with a different type of 3-D printing filament that combines plastic with iron, leveraging magnetic properties to invisibly encode static information in 3-D printed objects. This, they say, could be used in applications ranging from barcode identification for inventory purposes or providing information about an object that tells a robot how to interact with it.
“It looks like a regular 3-D printed object but there’s invisible information inside that can be read with your smartphone,” says Justin Chan, Allen School doctoral student and co-lead author of the paper.
For more, see “3D Printing Wireless Connected Objects.”
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