Scottish researchers have developed light sensitive sensors that could be used to control prosthetic limbs

Photodetectors for better control of artificial limbs

Wearable sensors detecting muscle contractions developed by Scottish researchers could help amputees gain better control over prosthetic limbs.

Developed by a team from the University of St Andrews, the device consists of a light source and four photodetectors made from semiconducting polymers arranged and assembled as a flexible bandage.

During their experiments, the researchers proved the detectors can measure the differences between the scatter of the light from a relaxed and contracted fibrous muscle.

If the muscle contracts, the scatter of the light drops as the muscle fibres move farther apart. The information can then be passed in the form of a photocurrent onto a robotic arm which then carries out the action in accordance with the state of the muscle.

"Wearable sensors are important for continuous monitoring of health and our approach offers the advantages of being non-invasive, lightweight, flexible and simple to make,” said Professor Ifor Samuel, who leads the team behind the invention at St Andrews University’s School of Physics and Astronomy.

"By using light we avoid needles that would be needed to make electrical contact. The muscle movements are detected directly by the optical sensor, providing a simple interface to control a prosthetic limb."

The research, described in the latest issue of the Advanced Materials journal, paves the way for future low-cost disposable optical sensors that would make the lives of amputees more comfortable. Currently, prosthetic limbs can be controlled by electrical sensors which could cause electromagnetic interference and even trigger immune system reactions.

"This sensor can distinguish between different types of contractions and can add extra functionality to active prosthetics, enabling natural movements of the limbs, which is not possible with currently available techniques," said Dr Ashu Bansal, a member of the research team.

The study was funded by the Engineering and Physical Sciences Research Council (EPSRC) and the Medical Research Council (MRC).

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