This sensor adapts its shape and can closely adhere to cortical surfaces, allowing users to record neural signals and stimulate specific brain regions via low intensity ultrasound waves.
"Previous research on brain sensors that contact the brain surface struggled with accurately measuring brain signals due to the inability to conform tightly to the brain's complex folds," Donghee Son, supervising author for the study, told Tech Xplore.
"This limitation made it difficult to precisely analyse the entire brain surface and accurately diagnose brain lesions. While a brain sensor previously developed by Professor John A. Rogers and Professor Dae-Hyeong Kim addressed this issue to some extent due to its extremely thin form, it still faced challenges in achieving tight adhesion in regions with severe curvature."
The sensor previously developed by Professors Rogers and Kim was found to collect more precise measurements on the brain's surface. Despite its promise, this sensor presented various limitations, such as failing to adhere to surfaces of the brain that had a larger curvature, as well as the proneness to slipping from its original attachment point due to micro-motions in the brain and the flow of cerebral spinal fluid (CSF).
These observed challenges limit its potential use in medical settings, as they reduce its ability to consistently measure brain signals in target regions for prolonged periods of time. As part of their study, Son and his colleagues set out to develop a new sensor that could overcome these limitations, adhering well to curved brain surfaces and thus enabling the reliable collection of measurements for extended time periods.
"The new sensor we developed can tightly conform to highly curved brain regions and adhere firmly to the brain tissue," said Son. "This strong adhesion allows for long-term and precise measurement of brain signals from targeted areas."
The sensor developed by Son and his colleagues, dubbed ECoG, adheres securely to brain tissue without forming any voids. This can significantly reduce the noise originating from external mechanical movements.
"This characteristic is particularly important in enhancing the effectiveness of epilepsy treatment through low-intensity focused ultrasound (LIFU)," said Son. "While it is well-known that the ultrasound can help minimise epileptic activity, the variability in patient conditions and the differences between individuals have posed significant challenges for tailoring treatments to each patient."
The shape-morphing and cortex-adhesive brain sensor developed by Son and his colleagues comprises three main layers. These include a hydrogel-based layer that can bond with tissue both physically and chemically, a self-healing polymer-based layer that can change its shape to match the shape of the surface below it, and a stretchable, ultrathin layer containing gold electrodes and interconnects.
The can attach to brain tissue securely while also adapting its shape to fit tightly onto brain surfaces, irrespective of their level of curvature minimising the vibrations produced by external ultrasound simulation. This could allow doctors to precisely measure the waves in their patients' brains both under normal conditions and during ultrasound simulation.
So far, the new sensor developed by Son and his colleagues has been tested on living and awake rodents. The findings collected were highly promising, as the team was able to precisely measure brain waves and control seizures in the animals.
The researchers eventually plan to scale the sensor, building on their design to create a high-density array. After it passes clinical trials, this upgraded sensor could diagnose and treat epilepsy or other neurological disorders while potentially paving the way for more effective prosthetic technologies.
