While rigid neural interfaces can read brain activity and stimulate it quite well, these devices end up damaging the soft brain tissue they come in contact with. Moreover, the body ends up attacking these implants and forming protective layers around them that quickly degrade the electrodes.
“Imagine you have a bowl of Jell-O, and you insert a rigid plastic fork into the bowl and move it around,” said Carnegie Mellon’s Christopher J. Bettinger. “It’s going to damage the Jell-O, producing defects and irreversible structural changes. That situation is analogous to inserting a rigid electronic probe into soft tissue such as someone’s brain. It’s a combination of what we call micro-motion and mechanics, which work together to not only damage the brain, but also compromise the function of the implanted sensor.”
Now Bettinger and his team at Carnegie Mellon University, working with colleagues at University of Pittsburgh, are reporting on new, hydrogel-based electrodes that can stick to brain tissue and closely match the organ’s softness and pliability. The electrodes are able to stimulate nearby neurons while mostly avoiding injuring cells in the vicinity and avoiding initiating the body’s defensive responses.
Some details about the material from the study abstract in Advanced Functional Materials:
Here, a strategy to fabricate an ultracompliant MEA is described based on aqueous‐phase transfer printing. This technique employs redox active adhesive motifs in hygroscopic polymer precursors that simultaneously form hydrogels through sol–gel phase transitions and bond to materials in the underlying microelectronic structures. Specifically, in situ gelation of four‐arm‐polyethylene glycol‐grafted catechol [PEG‐Dopa]4 hydrogels induced by oxidation using Fe3+ produces conformal adhesive contact with the underlying MEA, robust adhesion to electronic sub‐structures, and rapid dissolution of water‐soluble sacrificial release layers. MEAs are integrated on hydrogel‐based substrates to produce free‐standing ultracompliant neural probes, which are then laminated to the surface of the dorsal root ganglia in feline subjects to record single‐unit neural activity.
Study in Advanced Functional Materials: Ultracompliant Hydrogel‐Based Neural Interfaces Fabricated by Aqueous‐Phase Microtransfer Printing…