Researchers and engineers at Massachusetts Institute of Technology (MIT) are using 3D printing to develop soft, flexible brain electrodes using a conductive polymer liquid material. MIT engineers are working on monitoring brain activity with soft neural implants that will conform to the brain’s contours and not aggravate the area.
The current brain implants, usually metal, tend to cause irritation and the build up of scar tissue, with the team’s polymer electronics these issues could be avoided. The softer, safer and faster flexible polymer electronics could also be used to stimulate neural regions to help with the symptoms of epilepsy, Parkinson’s disease, and severe depression.
A recent published study by the team lead by Xuanhe Zhao, a professor of mechanical engineering and of civil and environmental engineering, has discussed how the team developed the flexible conducting polymers.
“These polymer solutions are easy to spray on electrical devices like touchscreens,” comments Hyunwoo Yuk, a graduate student in Zhao’s group at MIT. “But the liquid form is mostly for homogenous coatings, and it’s difficult to use this for any two-dimensional, high-resolution patterning. In 3D, it’s impossible.”
The paper introduces the 3D printable conducting polymer ink solution that uses polystyrene sulfonate thickened with nanofibers to be more like toothpaste so it can be 3D printed. “Initially, it’s like soap water,” Zhao states. “We condense the nanofibers and make it viscous like toothpaste, so we can squeeze it out as a thick, printable liquid.”
The team was able to successfully print with the conductive “toothpaste” into a stable pattern and used it to create a soft, rubbery electrode, which they implanted in the brain of a mouse, as a proof of concept. “We hope by demonstrating this proof of concept, people can use this technology to make different devices, quickly,” adds Yuk. “They can change the design, run the printing code, and generate a new design in 30 minutes. Hopefully, this will streamline the development of neural interfaces, fully made of soft materials.”
“The beauty of a conducting polymer hydrogel is, on top of its soft mechanical properties, it is made of hydrogel, which is ionically conductive, and also a porous sponge of nanofibers, which the ions can flow in and out of,” comments Baoyang Lu, a co-author on the study. “Because the electrode’s whole volume is active, its sensitivity is enhanced.”
Essop, Anas, et al. “MIT Engineers Use Conducting Polymers to 3D Print Soft and Flexible Brain Implants.” 3D Printing Industry, 21 Apr. 2020, 3dprintingindustry.com/news/mit-engineers-use-conducting-polymers-to-3d-print-soft-and-flexible-brain-implants-170956/.