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. Credit: Carnegie Mellon College of Engineering
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.
Now, Carnegie Mellon engineering researchers have fabricated the first stainless steel neural probe that allows for customizable, high-density neural recording, making brain readings much safer than before.
The team's work is published in the journal Nature Communications.
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 and 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 their toughness, which ultimately minimizes the risk of breakage."
Currently used in biomedical implants such as prosthetics and coronary stents, stainless steel is biocompatible, resilient, and less brittle. Credit: Carnegie Mellon College of Engineering
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 (steeltrodes) are microfabricated using a multilayer process enabling high-density electrode integration. 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 benefited 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 material and mechanical properties of stainless steel to design miniaturized biomedical devices such as high channel density neural probes with micron-scale features on stainless steel. Our devices are robust, reusable, customizable, and can be produced at scale."
In the future, the team hopes that neurosurgeons will be able to use multiple stainless steel probes on a patient in order to generate a more comprehensive recording of brain activity. Credit: Carnegie Mellon College of Engineering
This breakthrough is particularly important, both as a diagnostic tool and also as an intervention tool for patients with brain disorders such as epilepsy, Parkinson's Disease, and schizophrenia.
Zabir Ahmed, who worked on this project as part of his Ph.D. thesis at Carnegie Mellon University, is excited about the great potential of this platform technology, even beyond neural interfacing.
"Beyond creating robust stainless steel neural probes for clinical use, I'm excited that this work introduces a novel planar microfabrication process directly on steel," says Ahmed. "This manufacturing process could lead to a new class of resilient devices that integrate multiple functionalities on steel, which can be useful for a wide range of applications."
In addition to microfabrication on stainless steel, the team has also optimized post-fabrication processing and packaging.
"Designed for seamless integration, our packaging method works effortlessly with commercial stimulation and recording systems—making it easy for researchers and medical professionals to readily adopt our stainless steel devices," says Ibrahim Kimukin, a research scientist in Chamanzar's lab
"This research represents a step-change in how we can interface with the brain, achieving high-resolution recording and stimulation using robust, clinically scalable materials," said Vishal Jain, a research scientist in Chamanzar's lab. "I'm thrilled to have contributed to the design and validation of this technology, which bridges the gap between research-grade precision and real-world translational potential."
Outside the clinic, the probes also fill an important gap for neuroscience research. According to co-author Tobias Teichert, associate professor of psychiatry and bioengineering at the University of Pittsburgh, hand-made laminar electrodes have much lower density and can cost significantly higher.
"The design of these steeltrodes is an amazing advancement because they provide much higher channel count and density, yet at the same time, they can be mass produced at a fraction of the cost," says Teichert.
In the future, the team hopes that neurosurgeons will be able to use multiple stainless steel probes on a patient in order to generate a more comprehensive recording of brain activity.
"Using steeltrodes, one day we will be able to record neural activity across multiple areas of the brain with high resolution and minimal damage to the brain tissue," explains Chamanzar. "This crosshatch of neural recordings will change the diagnosis and treatment of brain diseases."
Publication details
Zabir Ahmed et al, Robust minimally-invasive microfabricated stainless steel neural interfaces for high resolution recording, Nature Communications (2026). DOI: 10.1038/s41467-025-67681-w
Provided by Carnegie Mellon University Electrical and Computer Engineering
