Scientists have created a material that could make the process of reading biological signals, from heartbeats to brainwaves, much more sensitive.

Organic electrochemical transistors (OECTs) are designed to measure signals created by electrical impulses in the body, such as heartbeats or brainwaves. However, they are currently only able to measure certain signals. A team led by researchers from Imperial College London in the UK has now created a material that measures signals in a different way to traditional OECTs, potentially paving the way for new biological sensor technologies.

Semiconducting materials can conduct electronic signals, carried by either electrons or their positively-charged counterparts, known as holes. Holes in this sense are the absence of electrons – the spaces within atoms that can be filled by electrons.

Electrons can be passed between atoms but so can holes. Materials that use primarily hole-driven transport are called 'p-type' materials, and those that use primarily electron-driven transport are called 'n-type' materials.

"These materials might be able to detect abnormalities in sodium and potassium ion concentrations in the brain, responsible for neuron diseases such as epilepsy."Alexander Giovannitti, Imperial College London

An 'ambipolar' material is a combination of both types, allowing the transport of holes and electrons within the same material, leading to potentially more sensitive devices. However, it has not previously been possible to create ambipolar materials that work in the body.

At the moment, the most sensitive OECTs use a material that can only transport holes. Electron transport is not possible in these devices because n-type materials readily break down in water-based environments like the human body.

But in a paper published in Nature Communications, the team report the first ambipolar OECT that can conduct both electrons and holes with high stability in water-based solutions. The team overcame the seemingly inherent instability of n-type materials in water by designing new structures that prevent electrons from engaging in side-reactions that would otherwise degrade the device.

These new devices can detect the positively-charged sodium and potassium ions that play a critical role in the firing of neurons, particularly in the brain. In the future, the team hope to be able to create materials tuned to detect particular ions, allowing the monitoring of ion-specific signals.

"Proving that an n-type organic electrochemical transistor can operate in water paves the way for new sensor electronics with improved sensitivity," said lead author Alexander Giovannitti, a PhD student under the supervision of Iain McCulloch in the Department of Chemistry and Centre for Plastic Electronics at Imperial. "It will also allow new applications, particularly in the sensing of biologically-important positive ions, which are not feasible with current devices. For example, these materials might be able to detect abnormalities in sodium and potassium ion concentrations in the brain, responsible for neuron diseases such as epilepsy."

This story is adapted from material from Imperial College London, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.