[ Medical Implants ]
[ Medical Implants ]
A breakthrough in brain sensing
The human brain is complex. Understanding deep brain function usually requires the insertion of probes that frequently result in irreversible tissue damage. Current neural probes are made out of silicon, a brittle material that can shatter during placement. Carnegie Mellon engineering researchers have fabricated the first stainless steel neural probe that allows for customizable, highdensity neural recording, making brain readings much safer than before.
By Krista Burns, Carnegie Mellon University( CMU)
Prof. Maysam Chamanzar with a stainless neural probe
Over the last few decades, novel manufacturing and microfabrication processes have revolutionized neural probe technology. Based in large part on the adaptation of silicon as the material of choice, it has been possible to increase recording channel density using high-resolution lithography and microfabrication processes, and to add new functionalities such as optical stimulation, imaging and chemical sensing. While existing silicon probes work well in thin, shallow tissue, its brittleness limits deep brain maneuvering. By creating probes made out of stainless steel, researchers are able to navigate to the middle brain with minimal cortical tissue damage, enabling inter- and intraoperative neural recording for epilepsy localization and deep-brain-stimulation implantation. The team is led by Maysam Chamanzar, the Dr. William D. and Nancy W. Strecker Career Development Professor of Electrical and Computer Engineering.“ High-resolution electrophysiology requires long, compact, high-density probes that are inserted with minimal invasiveness,” explains Chamanzar.“ Current silicon neural probe technology has a low fracture toughness and runs the risk of breaking during surgery, leaving residue behind in the brain. By fabricating high-density probes out of stainless steel, we are able to increase the length of the probes while strengthening its toughness, which ultimately minimizes the risk of breakage.”
Customizable probes Currently used in biomedical implants such as prosthetics and coronary stents, stainless steel is biocompatible, resilient, and less brittle. Though its microfabrication has been historically limited, Chamanzar has found a way to manufacture these probes in a customizable way. These novel, customizable stainless steel neural probes, or steeltrodes, that are microfabricated using a multilayer process which enables high-density electrode integration is the focus of a paper published in Nature Communications. The team has demonstrated successful high-resolution neural recording from the auditory cortex of test subjects. One hurdle the team had to overcome was the micro- and nanofabrication process for stainless steel. In the case of silicon probes, the fabrication process has benefitted from decades of research and development in the Micro- / Nano-Electromechanical Systems( MEMS / NEMS) and Complementary Metal – Oxide – Semiconductor( CMOS) electronic industries. However, the same processes cannot be readily translated to stainless steel. By using a multilayer fabrication process that enables high-density electrode integration, as well as optional flexible cables, Chamanzar believes these probes can be manufactured in mass.“ The micro- and nanofabrication processing for stainless steel is quite challenging and comparatively underdeveloped and underexplored,” explains Chamanzar.“ Optimized scalable microfabrication and micromachining processes are necessary to leverage the excellent
42 Stainless Steel World April 2026 www. stainless-steel-world. net