Body sensors signal 'new wave' healthcare

High-tech systems that allow doctors to monitor illnesses and injuries remotely are a step closer thanks to latest research. It could have a massive effect on the future of this field of healthcare.

The use of such compact, wireless and power-efficient body sensors — or biosensors — attached to the body for health monitoring is not new.

But antennas that enable such devices to be linked together efficiently on a patient’s body without wires are at present too uncomfortable to wear for long because they need to be large to maximise the strength of the signal being received.

They can be reduced in size but this leads to the antenna being less efficient, meaning that the battery powering the device has to be recharged more frequently.

Now, experts in antennas and bioelectromagnetics at Queen’s University Belfast (QUB) — with funding from the Engineering & Physical Sciences Research Council — have developed novel types of antenna that get around these limitations.

Bioelectromagnetics is the study of how living organisms interact with electromagnetic waves.

“Britain leads the world in the development of wearable communications including WBAN [wireless body area network] antennas,” said Dr William Scanlon who is heading the Queen’s University project in Northern Ireland. He believes it could change the way that a range of illnesses, injuries and conditions are monitored.

The university work could revolutionise the way patient care is provided, making unnecessary visits for tests and check-ups a thing of the past.

Instead, biosensors could gather data — on heart rate, respiration, posture, walk and so on — transmitting this information by radio signal to a control unit also on the patient’s body. The data could then be accessed by doctors via the internet or mobile phone, for example.

These types of antenna are the first in the world deliberately to harness what scientists call the 'creeping wave' effect.

With a conventional on-body antenna, most of the signal is transmitted either away from the patient or inwards, where it is absorbed by the patient’s body that weakens the signal.

The rest of the signal hugs the skin’s surface and 'creeps' around the body where it is picked up by the control unit.

But only a small amount of the signal behaves in this creeping way and thus its overall strength has to be increased to allow enough of it to reach the control unit.

Although traditional antenna designs can be used, they are physically large and typically protrude up to four centimetres from the body surface for the frequency bands used by systems such as Wi-Fi. Reducing the size leads to poor system efficiency.

The antennas developed at QUB solve these problems. They are specifically designed to accentuate the creeping wave effect by maximising the signal radiated to the antenna’s side, rather than inwards and outwards. They are up to 50 times more efficient than previously available designs of the same dimensions.

Because of the lower power requirement resulting from this step, the team has antenna thickness from 34 mm to less than 5 mm thickness for its new patch antenna, for example.

As a result, the antennas can be fitted almost anywhere on the patient without causing significant inconvenience and are sufficiently low profile to be incorporated into clothing or worn as part of a wound dressing.

The antenna design could unlock the full potential of emerging WBAN technology. A WBAN is a group of biosensors attached to different parts of a patient’s body.

Patients wearing a WBAN could carry on their normal lives and the doctor remotely monitoring the data gathered by the network would contact them to arrange appointments when needed.

WBANs also have many potential applications in other fields, such as monitoring the heartbeat, respiration and movement of firefighters as they tackle a blaze.

A key role in the research is being played by a specially designed reverberation chamber at QUB where the performance of wearable antennas can be studied under 'live' conditions and with unprecedented accuracy.