Over the past decade, a major trend in electronics has been the development of sensors, displays, and smart devices that are seamlessly integrated onto the human body. Most of these wearable devices are singularly connected to a user's smart phone and transmit all data via Bluetooth or Wi-Fi signals. But as consumers wear more wearable devices, and as the data they transmit increases in sophistication, more innovative connection methods are being sought.

Researchers from the National University of Singapore (NUS) have invented a new way for wearable devices to interconnect. They have incorporated conductive textiles into clothing to dynamically connect several wearable devices at once. This “wireless body sensor network” allows devices to transmit data with 1,000 times stronger signal than conventional technologies, meaning the battery life of all devices is dramatically improved. Wireless networks of these wearable devices on a body have future applications in health monitoring, medical interventions, and human-machine interfaces.

NUS researchers Tian Xi, Lee Pui Mun, and John Ho show their smart textiles.
From left: PhD student Mr Tian Xi, Research Fellow Dr Lee Pui Mun and Assistant Professor John Ho, together with seven NUS researchers, took a year to develop the 'smart' textiles.

Almost all body sensors, such as smart watches, connect to smartphones and other wearable electronics via radio waves, which radiate outward in all directions. This means most of the energy is lost to the surrounding area. This method of connectivity drastically reduces the efficiency of the wearable technology as most of its battery life is consumed in attempting the connection.

Assistant Professor John Ho and his team from the Institute for Health Innovation & Technology (NUS iHealthtech) and the NUS Faculty of Engineering wanted to confine the signals between the sensors closer to the body to improve efficiency. Their solution was to enhance regular clothing with conductive textiles known as metamaterials. Rather than sending waves into surrounding space, these metamaterials are able to create “surface waves” that glide wirelessly around the body on the clothes. This means the signal’s energy between devices is held close to the body rather than spread in all directions. Hence, the wearable electronics use much less power than normal, and the devices can detect much weaker signals.

"This innovation allows for the perfect transmission of data between devices at power levels that are 1,000 times reduced. 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," explained Assistant Professor Ho. In fact, the signal between devices is so strong that it’s possible to wirelessly transmit power from a smartphone to the device itself, opening the door for battery-free wearable devices.

Crucially, this signal boost does not require any changes to either the smartphone or the Bluetooth device; the metamaterial works with any existing wireless device in the designed frequency band.

This inventive way of networking devices also provides more privacy than conventional methods. Currently, radio waves transmit signals several meters outward from the person wearing the device, meaning that personal and sensitive information could be vulnerable to potential eavesdroppers. By confining the wireless communication signal to within 10 centimeters of the body, Ho and his team have created a more secure network.