A Sweater That Doubles as a Wi-Fi Booster? Researchers' Knitting Promises Smart Future Clothing
"Communities of knitters can come up with ingenious ways to integrate aesthetics and functionality into a sweater," says Nanfang Yu.
Researchers at Columbia University, North Carolina State University, and the City University of New York are looking to turn scarves and throws into functional antennas — showing off a low-cost flat-knitting platform capable of delivering soft antennas, perhaps one day leading to, in the lead researcher's words, "a sweater that can double as a Wi-Fi signal booster."
"The float-jacquard knitting technique used for making our textile metasurfaces is exactly the same technique that my mother used to make sweaters for me," project lead and corresponding author Nanfang Yu, associate professor of applied physics and applied mathematics, explains. "I still remember a purple sweater I wore as a kid that had a row of white cats across the chest; I remember that when I inspected the inner side of the sweater, I saw white parallel yarns — the floats."
Float-jacquard knitting is nothing new — as anyone with a Fair Isle sweater in their wardrobe will attest — but the novelty of the team's approach is in using it not for aesthetic purposes to to create functional metasurfaces with off-the-shelf metallic and dieletric yarns, on commercially-available knitting machines. To prove the concept, the team built two prototypes: a metasurface lens and a vortex-beam generating device, both functionalized during production of the fabric without requiring any separate processing — making them, the researchers say, low-cost and easily scalable.
To prove their functionality, the team used the prototype fabric metalens to both transmit and receive signals, while the vortex-beam generator delivered a transmission beam with a corkscrew-shaped wavefront — desirable, the researchers explain, as it can carry information independently of a traditional planar wavefront carrier, doubling the throughput of a given communications channel. In both cases, the antennas worked as expected — and withstood repeated folding, rolling, and even washing.
"It's important to stress that these devices were fabricated using commercially available off-the-shelf yarns and leveraging established fabrication techniques," Yu notes. "I am almost certain that communities of knitters can come up with ingenious ways to integrate aesthetics and functionality into a sweater — a sweater that can double as a Wi-Fi signal booster."
The team's work has been published in the journal Advanced Materials under closed-access terms.