A team of Chinese and Japanese researchers has developed a groundbreaking brain implant electrode array that is thinner than a human hair, as soft as brain tissue and capable of maintaining high-performance neural recordings for up to 18 months.
The innovation, which could significantly advance brain-computer interface technology, demonstrated exceptional durability and biocompatibility during animal trials, overcoming one of the biggest challenges facing long-term neural implants.
The research was led by Xu Xiaomin of Tsinghua University’s Shenzhen International Graduate School, alongside Takao Someya of the University of Tokyo and Li Xiaojian of the Shenzhen-Hong Kong Institute of Brain Science under the Chinese Academy of Sciences.
Their findings were published in the peer-reviewed journal Proceedings of the National Academy of Sciences (PNAS) and later highlighted by China Science Daily.
Addressing a Long-Standing Challenge
Brain-computer interfaces rely on implanted electrodes to capture neural signals, but conventional devices are typically made from rigid metals such as platinum or platinum-iridium alloys. While highly conductive, these materials are significantly stiffer than brain tissue, often causing inflammation, scarring and a gradual decline in signal quality over time.
To overcome this problem, the researchers developed a new material known as Conductive Hydrogel with Interfacial Percolation (Chip), which combines the flexibility of soft tissue with the conductivity of traditional metals.
According to the research team, the hydrogel achieved a record electrical conductivity of 2,512 Siemens per centimetre, making it the most conductive hydrogel ever reported.
Ultra-Thin, High-Density Design
Using advanced microfabrication techniques, the team created a 128-channel electrocorticography (ECoG) electrode array measuring just nine micrometres in thickness.
The implant features a channel density of 853 channels per square centimetre—more than ten times greater than previous hydrogel-based electrode designs.
Researchers said they overcame the common problem of hydrogel swelling by developing a specialised fabrication process that maintained the material’s structural stability while enabling high-precision patterning.
Successful Long-Term Animal Trials
To test the implant’s durability, researchers implanted the device into five rabbits and monitored neural activity for more than 550 days.
Throughout the trial period, the implant consistently delivered stable recordings, with signal quality remaining above 94 per cent of its original performance.
The material also showed remarkable mechanical resilience, maintaining stable electrical properties after undergoing 1,000 stretching cycles at 30 per cent strain—the maximum deformation typically experienced by brain tissue.
Laboratory tests involving porcine brain tissue further demonstrated that the implant could adhere gently to the brain’s surface and be removed without causing tissue damage.
Potential Future Applications
Histological examinations conducted after 16 weeks revealed minimal inflammation around the implanted devices, confirming their long-term compatibility with biological tissue.
The researchers believe the technology could pave the way for safer, longer-lasting brain implants for medical treatments, neurological research and future brain-machine interfaces.
They noted that the fabrication techniques developed during the study could also expand the use of advanced hydrogels in a wide range of bioelectronic devices, bringing scientists closer to achieving seamless integration between the human brain and digital systems.
