Members of the project team show the metamaterial designs in the wearable sensor network. Left to right: doctoral student Xi Tian, research fellow Pui Mun Lee, and senior author John Ho. (National University of Singapore)
17 July 2019. A new type of smart fabric can dramatically improve connectivity between wearable sensors and mobile devices compared to current wireless networks. A team of engineers and materials scientists at National University of Singapore describe their discoveries in today’s issue of the journal Nature Electronics (paid subscription required).
Researchers led by electrical and computer engineering professor John Ho are seeking to improve the efficiency and privacy of wearable electronic sensor networks, used increasingly to monitor vital signs and other indicators of a person’s health. Current technologies like Bluetooth can transmit signals wirelessly over a short distance, but they radiate the signals in all directions within range of a receiving device. Thus much more power is needed to transmit the signal than is needed to simply reach the receiver. Broadcasting the signal also raises risks of intercepting the data, which for health-related apps should be kept private.
Ho and colleagues from the university’s Institute of Health Innovation and Technology developed an alternative method of transmitting wearable data. Their process adds commercially-available conductive materials to fabrics worn by individuals that can transmit data in a more focused manner. These conductive fabrics, say the authors, make it possible to transmit data from sensors simultaneously to multiple receiving devices in a wireless body network, much more efficiently and privately than today’s broadcast signals.
The researchers created this network from metamaterials, composite materials with added properties not found in natural materials. In this case, the metamaterials are conductive flexible polymers fabricated into a design resembling a long comb, with radio frequency signals traveling as surface waves over the teeth of the comb. The comb strips are attached to fabrics, with a conductive layer underneath. Bluetooth or Wi-Fi signals from wearable sensors are sent through this network to receiving devices, rather than out in space searching for a nearby receiver. In this way, signals require much less power to reach their targets and are kept close to the body, within 10 centimeters.
The result, says Ho in a university statement, is a dramatic reduction in power needed for transmitting data from wearable sensors. “This innovation allows for the perfect transmission of data between devices at power levels that are 1,000 times reduced,” notes Ho. “Or, alternatively, these metamaterial textiles could boost the received signal by 1,000 times which could give you dramatically higher data rates for the same power.” The efficiency gained from these metamaterials may also make it possible to transmit power for wearable sensors through this network rather than building power sources into the sensors.
The researchers say the metamaterials are inexpensive and can be cut from rolls with lasers. Once added to fabrics with adhesives, the metamaterials can be laundered, dried, and folded with other clothing, while retaining their conductive properties. In addition, no changes are needed in smartphones or other receiving devices to connect to these whole body networks.
The university filed for a provisional patent on the technology and is seeking commercial partners. “We envision that endowing athletic wear, medical clothing, and other apparel with such advanced electromagnetic capabilities,” says Ho, “can enhance our ability to perceive and interact with the world around us.”
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