How NEO Makes the Battery-Free Epidural BCI

Despite being lesser known than its American and Australian counterparts, NEO remains one of my favourite BCI systems because of its design. Developed by Tsinghua University and Neuracle Technology, it solves two problems that constrain every other fully implantable neural interface.

First, it achieves minimal surgical invasiveness while remaining fully reversible. NEO's electrodes sit epidurally, outside the dura mater. This means no breach of the cerebrospinal fluid space, no penetrating arrays that trigger scarring, and no direct tissue damage. The implant can be removed without harming the brain.

Second, its power supply mechanism is appealing. There is no battery. An external coil on the scalp delivers power through near-field induction to receiver coils embedded in the skull. This eliminates degradation from charge cycles, removes the need for replacement surgeries, and enables theoretically unlimited device lifetime.

For all its conservatism, NEO achieves remarkable clinical results. A 54-year-old patient with complete C4 spinal cord injury achieved over 90% grasping accuracy across nine months of unsupervised home use. A second patient demonstrated decoder stability for over six months without recalibration.

NEO's published documentation is limited to two preprints and news coverage, and I have refrained from speculating or making inferences from published neuroengineering literature.

System Architecture

NEO consists of four implanted components and one external component.

Two flexible electrode strips are positioned over the right sensorimotor cortex, connected to a titanium package embedded in the skull. The electrodes measure 3.2 mm in diameter with 8 mm center-to-center spacing (Liu et al., 2024). These dimensions are large compared to micrometer-scale contacts in intracortical arrays, but necessary to maintain signal quality across the dural barrier.

Flexible ribbon adaptors route signals from each electrode strip to the titanium package embedded in the skull. This package, coin-sized at 25 mm diameter, contains the amplification electronics, analog-to-digital converters, and receiver coils for wireless power and data transmission. Hermetic sealing protects the electronics from the body and the titanium integrates directly with surrounding bone over time (Liu et al., 2024).

During use, an external transmitter coil attaches magnetically to the scalp directly above the implanted package. This external unit delivers power through inductive coupling and receives neural data wirelessly (Liu et al., 2024). When the user removes the external coil, the implant sits dormant with no battery drain and no activity.

Electrode Arrays

Neuracle Technology, headquartered in Changzhou with offices in Beijing, serves as NEO's manufacturing partner (Yicai Global, 2024). The electrodes are made of platinum-iridium alloy and the system is sealed with medical silicone (Liu et al., 2024) (Yao et al., 2025). Detailed fabrication methods have not been published.

Titanium Package and Electronics

The titanium package measures approximately 25 mm in diameter and embeds into a 3-4 mm deep groove machined into the skull, where it is fixed using bone screws (Liu et al., 2024). This positions the receiver coil close to the scalp for efficient power coupling.

NEO uses a titanium alloy package, though the specific alloy has not been disclosed (Liu et al., 2024). The system operates at a 1 kHz sampling rate, receives power through near-field inductive coupling, and transmits neural data via Bluetooth (Liu et al., 2024) (Yao et al., 2025). Beyond these parameters, detailed specifications of NEO's internal electronics have not been published.

The NEO preprints describe "electrode adaptors" connecting the electrodes to the implant and lead wires routed via micro-tunnels drilled through the skull (Yao et al., 2025). Specific feedthrough technology and interconnect construction have not been detailed.

Wireless Power and Data

The defining feature of NEO's architecture is battery-free operation. Near-field inductive coupling delivers power wirelessly through the intact scalp and skull (Liu et al., 2024) (Yao et al., 2025). The system uses separate pathways for power delivery (inductive coupling) and data transmission (Bluetooth) (Liu et al., 2024).

The implantable portion consists of a 25 mm-diameter titanium alloy package containing the electronics and a coil, sealed with medical silicone (Liu et al., 2024). The external coil attaches magnetically to the scalp to couple with the implanted coil for power transfer.

Specific design parameters, including coil specifications, operating frequency, power transfer efficiency, and data transmission rates, have not been disclosed.

Surgical Procedure

The first NEO implantation occurred on October 24, 2023 at Xuanwu Hospital in Beijing (Xinhua News Agency, 2024) (Global Times, 2024). Professor Hong Bo's team at Tsinghua University proposed the principle and design of minimally invasive BCI in 2013, spending ten years developing the system before human trials (Tsinghua University, 2024) (Medical Xpress, 2024).

NEO electrodes are placed unilaterally over the sensorimotor cortex. In the published cases, eight Pt-Ir electrodes (in two sets of four) were positioned epidurally over the hand area of the right sensorimotor cortex, covering primary motor cortex (M1) and primary somatosensory cortex (S1) (Yao et al., 2025).

The titanium implant is embedded on the outer surface of the skull, with electrode leads routed via micro-tunnels drilled through the bone to the epidural space (Yao et al., 2025).

Placement is guided by preoperative functional MRI and CT imaging. Activation regions from fMRI are projected onto a 3D cortical model to simulate electrode positioning, while CT images determine skull thickness suitable for the titanium implant. The surgical plan is transferred to a neuronavigation system to guide the procedure (Liu et al., 2024).

Decoder calibration required less than 10 minutes using a block design paradigm alternating between imagined grasping and resting. Both patients were discharged within approximately 10 days of surgery and continued rehabilitation training at home.

Clinical Results

NEO's first patient was a 54-year-old male with complete C4 spinal cord injury (AIS-A grade) resulting from a car accident 14 years earlier. While classified as a complete injury, the patient retained limited right arm function allowing constrained forearm movement, though hand motor function was absent (Liu et al., 2024). The system was implanted on October 24, 2023 at Xuanwu Hospital in Beijing. A second patient was implanted at Tiantan Hospital in December 2023 (Yao et al., 2025).

Performance

Over nine months of home use, the first patient achieved an average grasping detection F1-score of 0.91 and 100% success rate in object transfer tests (Liu et al., 2024). Overall grasping accuracy exceeded 90% (Xinhua News Agency, 2024). The system enabled daily activities including eating and drinking with a pneumatic glove driven by decoded neural signals.

Stability

For the first patient (Xuanwu Hospital), stable performance was documented over 9 months. The second patient (Tiantan Hospital) demonstrated neural recording stability for over 18 months, with decoder performance maintained for more than six months without recalibration (Yao et al., 2025).

Safety

Both patients were discharged within approximately 10 days of surgery and resumed home-based rehabilitation. Published reports indicate successful outcomes, though formal safety data with explicit complication rates have not been published. The epidural approach keeps electrodes on the dural surface without penetrating brain tissue.

References

1. Liu, D., et al. (2024). Reclaiming hand functions after complete spinal cord injury with epidural brain-computer interface. medRxiv. doi:10.1101/2024.09.05.24313041
2. Yicai Global, . (2024). Neuracle Technology and NEO brain-computer interface development. [Link]
3. Yao, R., et al. (2025). Fine grained two-dimensional cursor control with epidural minimally invasive brain-computer interface. medRxiv. doi:10.1101/2025.10.06.25337264
4. Xinhua News Agency, . (2024). Chinese scientists make breakthrough in brain-computer interface technology. [Link]
5. Global Times, . (2024). Chinese scientists make breakthrough in BCI-assisted rehabilitation trial, `showing higher safety than Musk's Telepathy'. [Link]
6. Tsinghua University, . (2024). Minimally invasive brain-computer interface may help those with tetraplegia restore hand functions. [Link]
7. Medical Xpress, . (2024). Minimally invasive brain-computer interface may help those with tetraplegia restore hand functions. [Link]