Due to the complexity of creating mechanical designs and the spatial constraints of the implanted sites, it is still challenging to understand three-dimensional (3D) brain networks by recording surface and intracortical sections of brain signals. However, existing methods for studying neurons in animal brains to better understand human brains all have limitations, from being too invasive to not detecting enough information.

A recently created pop-up electrode device could collect more detailed data about individual neurons and their interactions with each other while lowering the risk of brain tissue injury. This device, created by scientists at Pennsylvania State University, is a foldable and flexible 3D neural prosthesis.

The device enables the 3D mapping of complex neural circuits with high spatiotemporal dynamics from the intracortical to cortical region. It can map the 3D neural transmission through advanced designed four flexible parts, penetrating shafts and surface electrode arrays in one integrated system.

Scientists noted, “In addition to the unique design that appears in three dimensions after being inserted into the brain, their device also uses a combination of materials that have not been used in this particular way.”

“In particular, they used polyethylene glycol, a material that has been used before, as a biocompatible coating to create stiffness, which is not a purpose for which it has been used before.”

The device must be rigid so that it can be inserted into the brain. It also needs to be flexible once it’s in the brain. So scientists used a biodegradable coating that provides a rigid outer layer on the device. This stiff layer dissolves once the device is in the brain, restoring its initial flexibility.

Co-corresponding author Ki Jun Yu of Yonsei University in the Republic of Korea said: “Putting together the material structure and geometry of this device allows us to get input from the brain to study 3D neuron connectivity.”

Huanyu Cheng, James L. Henderson, Jr. Memorial Associate Professor of Engineering Science and Mechanics, said: “We demonstrate the potential capabilities to identify correlations of neural activities from the intracortical region to cortical regions through continuous monitoring of electrophysiological signals. We also took advantage of the device’s structural properties to record synchronized signals from single spikes which are elicited by unidirectional total whisker stimulation.”

“In addition to animal studies, some applications of the device use could be surgeries or treatments for diseases where you may not need to remove the device, but you want to make sure the device is biocompatible over a long period of time.” . It is beneficial to design the structure as small, soft and porous as possible so that it can penetrate brain tissue and use the device as a scaffold to grow on top of it, leading to a much better recovery. We also want to use biodegradable material that dissolves after use.”

Scientists now look forward to iterating on the design to make it useful not only for gaining a better understanding of the brain, but also for surgery and disease treatments.

Magazine reference:

  1. Lee, JY, Park, SH, Kim, Y. et al. Foldable three-dimensional neural electrode arrays for simultaneous brain interface of the cortical surface and intracortical multilayers. npj Flex Electron 6, 86 (2022). DOI: 10.1038/s41528-022-00219-y