More sensitive sensor introduced – capable of better detecting subtle signals like brainwaves, heartbeats, and more

Researchers from Imperial College London have announced the creation of a material that overcomes the limits of today’s organic electrochemical transistors (OECTs), a technology designed to measure signals created by electrical impulses in the body (e.g. brainwaves, heartbeats, etc.).

While the new material measures signals differently than OECTs, the team believes the two can be used in complementary circuits, thereby opening a host of possibilities for new biological sensor technologies.

For those unfamiliar, semiconducting material can conduct electrical signals carried by either electrons or holes (the positively charged counterparts to electrons). In this sense, holes are basically the absence of electrons. 

Now, electrons and holes can be passed between atoms. Materials that use primarily hole-driven transport are referred to as ‘p-type’ materials, while those that primarily use electron-driven transport are called ‘n-type’ materials. 

There is also a material referred to as ‘ambipolar’, which is the combination of both types — that is, it allows the transport of holes and electrons within the same material. The use of such material in test and measurement scenarios has led to more sensitive readings; however, it has not been possible to create ambipolar materials that can work in the body. 

Currently, the most sensitive OECTs use a ‘p-type’ material; electron transport has not been possible since n-type materials break down in water-based environments like the human body.

So, with all of this now being understood, what the team introduced is an ambipolar OECT that can conduct holes and electrons in water-based solutions. Their work was published in Nature Communications . 

The researchers overcame the instability of n-type materials in water by designing new structures which prevent electrons from engaging in side-reactions, as this would lead to a degradation of the device itself. 

The new device can detect positively charged sodium and potassium ions, which are considered important for neuron activities in the body, especially in the brain. Looking ahead, the team hopes to create materials tuned to detect specific ions, as this would allow for ion-specific signals to be detected.

“Proving that an n-type organic electrochemical transistor can operate in water paves the way for new sensor electronics with improved sensitivity,” says lead author Alexander Giovannitti, a PhD student under the supervision of Professor Iain McCulloch, from 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.” 

Via Imperial College London