In brain-computer interfaces (BCIs) and other neural implant systems, electrodes serve as the critical interface and are core sensors linking electronic devices with biological nervous systems. Most currently implanted electrodes are static: Once positioned, they remain fixed, sampling neural activity from only a limited region. Over time, they often elicit immune responses, suffer signal degradation, or fail entirely, which has hindered the broader application and transformative potential of BCIs.
In a study published in Nature on September 17, a team led by Prof. LIU Zhiyuan, Prof. XU Tiantian and Assoc. Prof. HAN Fei from the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences, along with Prof. YAN Wei from Donghua University, reported a soft, movable, long-term implantable fiber electrode called "NeuroWorm," marking a radical shift for bioelectronic interfaces from static operation to dynamic operation and from passive recording to active, intelligent exploration.
The design of NeuroWorm is inspired by the earthworm's flexible locomotion and segmented sensory system. By employing sophisticated electrode patterning and a rolling technique, the researchers transformed a two-dimensional array on an ultrathin flexible polymer into a tiny fiber approximately 200 micrometers in diameter.
This miniature NeuroWorm integrated up to 60 independent signal channels along its length, resembling a highly sophisticated sensory highway. Crucially, the tip of the fiber was equipped with a small magnetic module, enabling wireless steering of the implanted device via external magnetic fields. With this setup, NeuroWorm effectively recorded high-quality spatiotemporal signals in situ while being steered within the brain or along muscle tissue as needed.
To validate NeuroWorm's ability to navigate within muscle fascia, the researchers implanted it through a minimally invasive, half-centimeter incision in a rat and then used external magnets to guide its daily movement across muscle surfaces. X-ray images showed the biomimetic motion, which resembles a microscale bionic worm gliding smoothly between tissue layers. During the seven-day post-implantation period, the device demonstrated the capability to relocate across various positions while concurrently capturing clear and stable electromyographic (EMG) signals from all channels. This functionality effectively realizes dynamic and precise monitoring with the principle of "measurement on demand at targeted locations."
The researchers implanted a single NeuroWorm in a rat's leg muscle for over 43 weeks, during which it continuously and stably recorded EMG signals. The fibrotic encapsulation thickness was less than 23 micrometers, much thinner than the 451 micrometers typically observed with conventional rigid electrodes. In addition, the researchers navigated the NeuroWorm through a rabbit's brain, guiding it from the cortex into subcortical regions while capturing high-quality neural signals throughout its trajectory. These examples underscore the device's biocompatibility and long-term stability.
This study provides a solution to enable noninvasive repositioning of implants via magnetic guidance, potentially eliminating surgeries due to drift or misplacement. NeuroWorm offers a smarter, more soft, and less invasive platform for long-term, multisite neural monitoring with potential applications in BCls, smart prosthetics, epilepsy mapping, and the management of chronic neurological disorders.
