Researchers at Penn State University have developed a method to create 3D-printed soft electrodes that can conform to an individual brain surface to provide more accurate patient-specific tracking of biophysical signals in the brain. The study, published in Advanced Materials, details a new technique to create neural interfaces that improve upon current stiff methods to more closely conform to the complex structure of the brain.
“Each person has a different brain structure, depending on their height, weight, age, sex and more,” said Tao Zhou, PhD, Wormley Family Early Career Professor and corresponding author of the study. “Despite this, we try to fit neural interfaces onto brains like they have identical structures. This motivated us to create electrodes that are tailored for each individual, based on the structure of their brain.”
The new electrodes are created using hydrogel, a water-rich material that has properties similar to brain tissue, and built in a honeycomb-like internal structure to help balance flexibility and strength. These soft electrodes, dubbed HiPGE for honeycomb-inspired printable gel electrodes, are fabricated using a 3-D printing method called direct ink writing, which allows for precise shaping at very small scales. The honeycomb design reduces stiffness allowing the electrodes to stretch and conform to the brain’s ridges and grooves without damaging brain tissue.
To individualize the design process, a patient would first have an MRI scan, which is used to create detailed simulations of each brain scanned. The simulations inform the how to create the shape of each electrode so it aligns with the patient’s specific cortical folds. The team then 3D prints both the electrode and a model of the brain to test how closely the device fits. In experiments involving 21 human brain models, the printed electrodes demonstrated improved conformity compared to traditional designs.
“The unique gyral patterns of the human brain demand patient-specific neural interfaces to achieve precise neuromodulation, mitigate adverse tissue responses, and optimize therapeutic efficacy and safety,” the researchers wrote, noting that conventional rigid electrodes “exhibit limited conformability to the brain’s heterogeneous cortical topography,” resulting in “poor electrode-tissue contact, signal loss, and foreign body responses.”
To evaluate HiPGE performance and biological compatibility, the researchers conducted 28-day in vivo tests in rat models. Results from the tests showed that electrodes maintained stable function for the entire the testing period and did not trigger an immune response. The flexible electrodes also provided consistent and accurate readings of electrical and physiological signals in the brain.
Prior research has studied soft-material neural interfaces, but customization to individual gyral patterns has been limited. The introduction of a combined imaging, modeling and printing design workflow has solved this limitation by enabling electrodes to be tailored at the patient level.
The researchers wrote that the folded structure of the brain “creates a unique ‘fingerprint’ for each brain.” They also noted that current rigid devices can lead to “signal degradation due to scar formation,” and can create instability caused by the mismatch between the stiff neural interface materials and soft brain tissue.
Clinically, the improved contact between electrode and brain tissue could provide more reliable monitoring of neural activity, an important improvement for diagnosing and managing neurological conditions. Better signal fidelity could enhance applications such as brain-computer interfaces, neuroprosthetics, and neuromodulation therapies. The soft, conformable design may also reduce complications associated with long-term implantation, including inflammation and tissue damage.
“This tailored design ensures robust electrode-tissue integration, minimizing mechanical mismatch and improving signal fidelity during in vivo neural activity recording,” the researchers wrote. They added that studies “confirmed HiPGE’s biocompatibility, revealing no significant immune response or structural disruption to brain tissue.”
Future research will seek refine the technology for specific disease monitoring and exploring its use in clinical settings. They also aim to optimize the devices for targeted neurological conditions, which could inform the development of more precise and individualized care strategies.
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