HMN 2026: How Spinal cord stimulator stays rigid for surgery, then softens inside the body

What if chronic diseases, which are difficult to treat with medicine alone, could be managed with electricity? As “neuromodulation”—a technology that restores bodily balance by sending signals directly to nerves—gains attention, a Korean research team has brought this possibility one step closer to reality.

A new kind of spinal implant

A research team led by Professor Sung-Min Park (Department of IT Convergence Engineering, Mechanical Engineering, Electrical Engineering, and Graduate School of Convergence Science and Technology) and Dr. Sunguk Hong (Department of Mechanical Engineering) at POSTECH (Pohang University of Science and Technology) has developed a spinal cord stimulator that remains rigid during insertion but softens upon contact with bodily fluids.

The findings are published in npj Flexible Electronics.

Chronic diseases like hypertension and diabetes are often attributed to lifestyle or genetics. However, recently, the medical community has increasingly recognized “neural imbalance” as a fundamental cause. This is why neuromodulation—restoring the body’s regulatory functions by sending electrical signals directly to nerves—is emerging as a powerful alternative to traditional drug therapy.

The core component of neuromodulation is the neural interface that attaches closely with nerves. The challenge has been a paradox: the device must be rigid enough to accurately pass through the narrow spinal canal during insertion, yet soft enough to mimic surrounding nerve tissue once placed.

The research team’s solution is “transformation.” By applying a variable stiffness structure using a water-soluble “sacrificial layer,” the device is designed to remain rigid during insertion and soften within minutes upon contact with bodily fluids.

Much like a hard medicinal capsule dissolves in the stomach to release its contents, this device reacts to its environment to change its physical state. Once softened, the device conforms closely to the spinal cord and moves naturally with the neural tissue.

Liquid metal for stable signals

The team also improved the method of electrical transmission. Instead of “solid metals,” which can cause unstable signals as resistance changes with body movement, the researchers utilized liquid metal. Liquid metal maintains its electrical properties even when its shape changes, allowing for stable signal transmission in dynamic environments.

Furthermore, they succeeded in reducing costs. Traditional neural interfaces are expensive due to high-cost semiconductor processes and the use of gold materials. However, the team significantly lowered manufacturing costs by using liquid metal and laser processing technologies.

Testing in animals and future uses

When attached to the spinal cords of rats to regulate the sympathetic nervous system, the device successfully reduced blood pressure and stably recorded sensory signals triggered by painful stimuli to the paw. This confirmed its potential as a “bidirectional neural interface” capable of both electrical stimulation and signal measurement.

The applications of this technology are vast. It could provide new options for patients who face limitations or side effects from drug treatments, including epilepsy and depression via vagus nerve stimulation, hypertension and paralysis rehabilitation via spinal cord stimulation, and overactive bladder via tibial nerve stimulation.

Professor Sung-Min Park, who led the study, said, “This is a neural interface technology that combines mechanical and electrical performance alongside the convenience required in clinical settings,” adding, “It is noteworthy for its potential to evolve into an intelligent neuromodulation system for treating chronic diseases.”

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