Minnetronix, the St. Paul-based contract manufacturer of electromechanical components and devices for other medical technology companies, has raised a $20 million stake from a big health care investor to help bring to market its first proprietary product.

Altaris Capital Partners, a New York equity firm, has acquired a minority position in Minnetronix, which is being announced Tuesday. The firm has $1.3 billion invested in health care concerns.

"We've developed technologies large and small, largely for other companies, and we see a growing need for innovative technologies in underserved areas that tend to be overlooked because they aren't multibillion-dollar markets," said Minnetronix CEO Rich Nazarian. "We believe this is an important business niche, and the investment … will help us accelerate our mission to develop and deliver devices that benefit patients and the physicians who care for them."

Minnetronix, an employee-owned company with 200-plus workers that had more than $60 million in revenue in 2015, said the investment by Altaris is the first outside equity it has raised since its founding 20 years ago.

Minnetronix is working on its Cerebrospinal Fluid Treatment Platform, a device used to filter red blood cells and other foreign bodies out of cerebrospinal fluid around the brain and spinal cord after a ruptured aneurysm.

Quickly filtering out cells that shouldn't be in the fluid after an aneurysm ruptures is thought to improve patient outcomes and shorten hospital stays by reducing another complication called vasospasm, or narrowing of the cerebral arteries, that may lead to permanent disability or death, the Minnetronix website says.

The treatment is aimed at stopping the bleeding, cleansing the blood, restoring normal flow and relieving the pressure on the brain.

The Cerebrospinal Fluid Treatment Platform, now being previewed with doctors and clinics, offers a tailored process for a proprietary treatment and return of cerebrospinal fluid called "neurapheresis."

The company hopes to enter clinical trials this year and commercialize what could be the first of several possible applications by 2017-18.

Minnetronix says neurapheresis works more efficiently than typical gravity-dependent drains in removing degraded red blood cells and their released cytotoxic byproducts.

"We're in a fairly 'under-innovated' space," said Chief Financial Officer Phil Ankeny.

"There's so much medical device investment in cardiovascular and orthopedics," Ankeny said. "In neurology, the physicians are thrilled to see this. There's real patient need and we're learning the platform we're developing has other potential uses, derivative products, than what envisioned."

Chief Operating Officer Jeremy Maniak said the technology is disruptive, in that it fills an unmet need. "Doctors try to manage the patients and keep them in the hospital for a long time … run images on them … and it can occur over 10-14 days. Our ultimate vision is a better outcome for patients, run them through therapy for a day or two and then send them home rather than being in the hospital and treatment for $4,000 a day."

Staff Writer Joe Carlson contributed to this report