A team of biomedical engineers have developed a fully flexible light sensor that precisely detects changes in the body's electrical signals.
For people living with cardiac or neurological conditions, monitoring organ activity is an important part of diagnosis and treatment. But existing technology relies heavily on electrically based systems that often require a network of electrodes to be attached directly to the organ site.
Now, a team of UNSW engineers from UNSW School of Biomedical Engineering have developed a fully flexible 'optrode' - an optical sensor that converts the body's electrical signals directly into light signals. Designed to mimic the softness of human tissue, the device demonstrated a 98.4% viability rate, paving the way for safer and less invasive long-term monitoring technologies.
The research team, who published their latest findings in npj Flexible Electronics , says the new sensor, which has only been tested on animals so far, could transform how the human body is mapped by delivering clearer and more precise insights into electrical activity.
"Bioelectronic implants are devices that can be placed in the body to monitor electrical signals from organs like the heart and brain. They help doctors track changes and patterns in a person's health over the short and long term," says first author of the paper, Dr Reem Almsari from UNSW School of Biomedical Engineering.
"They're usually made of rigid materials like silicon and metal and because our internal organs are soft and constantly moving, this mechanical mismatch often leads to tissue damage, scarring, and even the body 'rejecting' the implant.
"They also rely on metal wires that can break when bent or pick up a lot of electrical 'noise' from the environment, compromising data quality.
"Our new sensor overcomes these challenges and marks a major leap forward in the next generation of implantable bioelectronics."
New material, new design
The researchers replaced rigid, brittle components with soft high-performance polymers, which are materials engineered to safely interact with the body. This also includes a specialised conductive polymer that stays functional even after being bent 10,000 times.
Sandwiched in the middle is a layer of highly sensitive liquid crystals that can pick up amplitudes, or the magnitude, of a signal at the sub millivolts - similar to levels produced from the brain and heart.
"We engineered this system so that the crystals orientate their angle depending on the amplitude of the applied signal - for example, a brain signal," says Dr Almasri.
"Using light signals, it measures the percentage of change and converts it into quantifiable optical outputs."
Unlike traditional sensors, this device doesn't need local electronics or bulky wires at the tissue site to work, making it immune to electrical interference - a major issue in current bioelectronic devices.
"Amplifiers can help reduce electrical interference and improve signal quality at the site. However, they are often bulky and can generate heat around the surrounding tissue, potentially limiting the system's performance," says Dr Almasri.
"Once you reduce the size of the electrode, it becomes harder to seperate the signal from background electrical noise.
"In our technology, we can scale the sensor down to tens of microns - about half the width of a human hair - without losing signal quality or introducing any extra electrical noise."
Non-toxic to the body
The researchers also tested how well the flexible optrodes can live in cell cultures, examining if the cells still remain healthy, grow normally and safely function without any harm. They found no signs of toxicity or contamination.
"Our in vitro tests showed the optrode did not affect cell growth and viability when compared with silicon controls, which are widely used in current biomonitoring devices," says Dr Reem Almasri.
"As silicon is thicker and more rigid than our device, it can potentially restrict or inhibit cell growth to a greater extent."
Next steps
With support from the Tyree Foundation Institute of Health Engineering (IHealthE) at UNSW, the team behind the research is actively accelerating the commercialisation of the technology through their spin-out company, Sevren Pty Ltd , which was founded by Prof. Nigel Lovell and Prof. Francois Ladouceur from UNSW School of Biomedical Engineering.
Despite validating the sensor capability through animal testing, further in vivo studies are a critical next step to improve the signal resolution.
Beyond the heart and brain, this technology could be adapted for monitoring the gut, muscles, or even individual cells.
"We want to expand the bandwidth of the signal beyond 10 Kilohertz to capture the firing of individual neurons," says Dr Almasri.
"There's also opportunity to also improve the alignment of the liquid crystals. If we increase the sensitivity of the device, we could detect signals at the micron level."
This work was supported by a National Intelligence Discovery Grant, an Australian Research Council Discovery Grant, and an NHMRC Ideas Grant.
