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Medical sensors' potential for industry

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A REVOLUTIONARY type of sensor device that will allow doctors to monitor patients' hearts without even touching them could also soon be used to test carbon composite aircraft parts and microchips for defects more accurately and easily, thanks to new research by the inventors.

A team at the University of Sussex, southern England, has already successfully developed laboratory prototypes for these applications using electric potential sensor (EPS) equipment.

Similar devices that measure magnetic fields already exist. EPS offers a non-invasive way of measuring the lesser-explored electric fields that are present wherever there is electrical activity, including in the human body.

The EPS monitor gives precise readings of electrical activity of the heart without the need to connect the patient to equipment via pads and wires. A reading can be taken from the tip of a finger or remotely - a heartbeat can even be detected from up to a metre away in the laboratory.

"This contrasts with conventional ECG detectors where a highly conductive connection is required," said the research team's Dr Robert Prance. "We have implemented an ambulatory ECG system comprising wrist-mounted sensors and wireless transmission of the ECG. We have also developed a 2D [two-dimensional] sensor array that is capable of mapping the electrical signal from the heart across the chest.

"The sensitivity of these probes is now at a level to allow their use in the detection of brain signals [EEG], evoked responses, nerve fibre signals and muscle signals [EMG]. We are able to detect alpha and beta rhythms in the brain, as well as the alpha-blocking phenomenon, and also the optical muscle signal generated when the eye is moved [EOG]. In all cases, we require no resistive contact with the skin, or removal of body hair."

The researchers' aim is to simplify the procedure for acquiring high quality signals. The monitor is not commercially available yet and will be subject to patent licensing and further clinical trials in the near future.

The team from the Centre for Physical Electronics & Quantum Technology in the Department of Engineering & Design - Dr Prance, Dr Christopher Harland and Dr Helen Prance - has recently been awarded funding of 762,000 pounds by the UK's Engineering & Physical Sciences Research Council (EPSRC) to investigate many areas for which EPS technology could be adapted, including other aspects of medical science, aviation, microchip manufacture and the automotive industry.

The four-year project, which follows on from a million-pound EPSRC-funded basic technology research programme, will involve setting up pilot schemes with other scientists and businesses to develop a range of specific prototypes and test them.

Dr Prance added: "The funding enables the centre to consolidate research activity in a wide range of areas and to engage with appropriate academic and commercial partners. It is our belief that this non-contact technology will form the basis for new imaging instruments which will impact on both research and routine monitoring in many areas of science and technology."

The same technology has also been adapted to test for faults in microchip circuitry and even in stainless steel, carbon fibre composites and aircraft parts. EPS technology could also help to enhance MRI scanning techniques in hospitals.

The generic electric potential sensor was created and patented by the Sussex University team. As part of their programme they have already improved radically the overall performance of individual sensors - that is, in terms of noise level, input impedance and bandwidth.

The sensors can be used individually and in array format for imaging applications - either at the sub-micron level or on a much larger spatial scale, typically for application to non-destructive testing of materials or geophysical surveying.

The ultra-high input impedance electric potential sensors are suitable for characterising the structural properties of both conductors and insulators. To show this, the team has constructed a three-axis scanning instrument, which incorporates one of the sensors, to allow the non-destructive evaluation of faults and defects in metal structures.

The technology has also detected strain faults in metal bars prior to failure, simulated corrosion pits in both steel and aluminium samples and faults in steel and aluminium welds.

The researchers have demonstrated that their technology is particularly applicable to both composite materials and ceramics, where conventional methods such as eddy current testing are less effective. In particular, they are investigating the use of EPS devices to study delaminations in carbon composite materials and defects in brittle, powder-based alloys, as used in the machining industry.

One area of development for electric potential sensors is a scanning microscope system. This has been used to image the electrical signals within a high-speed digital circuit, the conduction paths in an integrated circuit and the dielectric properties of materials.

The team has also detected the time delay of a pulse propagated through saline, as a precursor to the study of conduction mechanisms in biological cells. The microscope can be set up with an 8-element linear array of sensors for faster data acquisition.

The Sussex group includes physicists, engineers and computational scientists. In addition to the EPS programme, they are also developing room-temperature induction magnetometer systems that can equal the magnetic field sensitivity of cryogenic Squid (superconducting quantum interference device) magnetometers.

London Press Service



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