A team of researchers, led by IMB-CNM-CSIC and ICN2, has developed a graphene-based bidirectional neural interface that can simultaneously record and modulate brain activity, overcoming a longstanding limitation in neurotechnology. The device combines graphene solution-gated field-effect transistors (gSGFETs) with nanoporous reduced graphene oxide (rGO) microelectrodes in a single, flexible platform, enabling both high-sensitivity monitoring and effective stimulation.
Neural interfaces are already used clinically to treat neurological disorders, but most current systems remain unidirectional. They typically deliver stimulation using fixed parameters, without the ability to adapt in real time to ongoing brain activity. Even in systems that can both stimulate and record, performance is often constrained - particularly when it comes to detecting very low-frequency signals, which are increasingly recognized as important biomarkers. The newly reported device addresses these challenges by integrating two complementary graphene technologies.
Graphene transistors (gSGFETs) provide high-fidelity recording capabilities, including sensitivity to infraslow brain activity and local field potentials. Unlike conventional electrodes, these transistors enable multiplexed operation and extend recording bandwidth toward very low frequencies. However, their limited charge injection capacity makes them unsuitable for stimulation. To overcome this, the researchers incorporated nanoporous rGO microelectrodes, which offer high charge-injection capacity for focal electrical stimulation. By combining these elements monolithically using scalable cleanroom microfabrication techniques, the team created a fully flexible neural probe that leverages the strengths of both components within a single device.
A key technical challenge was avoiding interference between stimulation and recording. In previous approaches, electrical stimulation pulses often introduced artifacts that masked or distorted neural signals. In this work, the hybrid architecture was specifically designed to preserve signal integrity during operation. As Dr. Anton Guimerà explains, "integrating both transistors and electrodes makes bidirectional communication more sensitive and precise. The results showed that monitoring brain activity, including ultra-low frequency activity, is not affected by modulation. For this reason, we can say that the device is able to listen and speak."
Performance was evaluated both in saline and in vivo, with experiments conducted in mouse models at University College London. The results show that the recording capability - including detection of infraslow activity- is maintained during simultaneous stimulation. This confirms that the device can operate in true bidirectional mode without compromising signal quality.
The system builds on earlier milestones from the same collaboration, including a 2018 demonstration of graphene-based implants capable of recording extremely low-frequency brain signals, and subsequent advances in nanoporous graphene electrodes. These developments have been supported by a long-standing partnership between IMB-CNM-CSIC and ICN2, and have contributed to the creation of INBRAIN Neuroelectronics, a spin-off focused on clinical translation.
By enabling simultaneous, artifact-free recording and stimulation, the new platform opens the door to adaptive neuromodulation strategies that respond dynamically to brain activity. In particular, the ability to monitor and act on infraslow signals could support the development of more precise, patient-specific therapies for neurological disorders.
