Think about how a plastic lid on a take-out coffee cup can be molded into different shapes to fit snugly. Researchers at Pusan National University used a similar idea on a very tiny scale to make better “neural interfaces,” which are small devices that help doctors connect with nerves or parts of the brain. Their invention is called microelectrothermoforming (μETF), and it shapes flexible materials into 3D forms — like domes, wells, and triangles — that can fit perfectly against curved tissues such as the retina or the surface of the brain. Their study appears in the journal npj Flexible Electronics.
Neural interfaces, including microelectrode arrays (MEAs), play a significant role in recording brain activity and delivering targeted stimulation. However, most existing MEAs feature flat designs that make it difficult to maintain close contact with rounded tissues. Current solutions often require multiple manufacturing stages, adding complexity and limiting the range of shapes that can be produced.
Pusan National University researchers developed a novel microelectrothermoforming (μETF) technique to fabricate flexible microelectrode arrays (MEAs) with 3D structures. This one-step process improves electrode-neuron proximity, lowering stimulation thresholds and enhancing neural recording and stimulation precision for applications like artificial retinas and brain-computer interfaces.
The new μETF method addresses these issues by leveraging principles similar to plastic thermoforming, a process commonly used in everyday items like coffee cup lids.
“The idea for this study came from a simple observation of plastic lids on take-out coffee cups. I realized that this plastic-forming method could be applied at a microscopic level to create 3D structures for neural electrodes,”
To carry out the process, researchers heat a thin, flexible polymer sheet — specifically liquid crystal polymer (LCP) — that contains embedded microelectrodes. The heated sheet is pressed against a 3D-printed mold in a single fabrication step, producing elevated or indented shapes, such as wells or domes. This design allows the electrodes to fit closer to target neurons while maintaining electrical function.
In proof-of-concept testing, the team created a 3D MEA intended for use in artificial retinas for blind patients. Simulations and experiments indicated a 1.7-fold reduction in the level of electrical stimulation needed compared to conventional flat electrodes and a 2.2-fold improvement in spatial precision. “Our 3D structures bring the electrodes closer to target neurons, making stimulation more efficient and precise,” says Associate Professor Kyungsik Eom, a co-leader on the project.
While the team has initially focused on retinal stimulation, they suggest the method could prove useful in brain, spinal cord, and peripheral nerve applications. One potential area of interest is brain-computer interfaces (BCIs) designed to help paralyzed patients control external devices, such as robotic arms, by translating neural signals into physical actions.
Looking ahead, the researchers plan to refine the fabrication process and explore broader medical applications, as well as possible uses beyond neural interfaces, including wearable electronics and organ-on-a-chip systems.
While there are other 3D or flexible microelectrode technologies in development, μETF stands out because it achieves complex 3D structures in a single thermoforming step, potentially making neural interfaces both more effective and easier to manufacture at scale.
Reference
•Title of original paper: “Microelectrothermoforming (μETF): one-step versatile 3D shaping of flexible microelectronics for enhanced neural interfaces”
•Journal: npj Flexible Electronics
