Efficient neuro-modulation chips to advance a new era of brain-computer interfaces

Researchers have developed a novel high-voltage 8-channel neural stimulation chip capable of exponential waveform output, achieving 98% output power efficiency and advanced charge-balancing capabilities. Published in Neuroelectronics, this breakthrough has the potential to improve neural modulation and brain-machine interface devices, ensuring safer and more effective treatments for neurological conditions.

Neural modulation offers significant promise in treating conditions like Parkinson's disease, epilepsy, and motor dysfunction resulting from spinal injuries. However, delivering electrical stimulus to neurons requires precise control to avoid tissue damage while maintaining high efficiency. Addressing this challenge, Professor Biao Sun from Tianjin University and Associate Professor Xu Liu from Beijing University of Technology, in collaboration with researchers from Tianjin University of Traditional Chinese Medicine and Southern University of Science and Technology, have developed a state-of-the-art 8-channel neural stimulation chip that enhances both safety and power efficiency in neural modulation systems.

“This chip design marks a critical advancement in neural modulation,” explains Professor Biao Sun. “With 98% power efficiency and a robust charge-balancing mechanism, this device safely stimulates neurons without causing harmful tissue damage, even in high-voltage applications.”

The newly developed chip delivers exponentially decaying currents, which are more power-efficient than traditional constant-current stimulators. Its 30-volt output stage ensures compatibility with high-impedance electrodes, which are common in modern neural stimulation applications. Lead researcher Xu Liu emphasizes, "The exponential waveform output significantly boosts efficiency and charge transfer, overcoming the challenges posed by high-impedance electrodes."

A major challenge in neural stimulation is charge imbalance, which can lead to ion imbalance and tissue damage. The team addressed this by integrating a dual-slope control scheme and an active charge-balancing circuit into each channel, reducing residual charge to less than 3 nC during each stimulation cycle.

The chip, fabricated using 180-nm BCD CMOS process technology with a core area of 13.25 mm², underwent extensive testing. Led by Shenjun Wang, Lin Zheng, and Xue Zhao from Tianjin University of Traditional Chinese Medicine, the team demonstrated that the stimulator effectively triggers action potentials and induces muscle contractions. Their measurements confirmed stable, multi-cycle outputs without residual charge accumulation.

In animal experiments, the chip successfully stimulated the vagus and sciatic nerves of anesthetized rats, showing its ability to induce precise motor responses without tissue damage. These tests, conducted in collaboration with Professor Hao Yu and Liuyang Zhang from the Southern University of Science and Technology, validated the device's performance in a biological setting.

“This chip has the potential to significantly impact the development of brain-machine interface systems and other biomedical devices,” says Professor Hao Yu. “Its high power efficiency and charge-balancing capabilities could lead to safer and more effective treatments for a wide range of neurological conditions.”

In addition to medical applications, the techniques in chip design could inspire innovations in industrial settings requiring precise electrical stimulation, such as advanced prosthetics or bioelectronic devices.

The neural stimulation chip achieves exceptional performance, with 98.1% power efficiency at a 20V output and a charge imbalance as low as 2.9 nC. It operates effectively at up to 30V, ensuring compatibility with high-impedance electrode-tissue interface and offering both exponential and constant-current stimulation modes. “This design might set a new standard for power efficiency and safety in neural stimulation,” notes Professor Biao Sun.

While the team acknowledges the need for further refinement in capturing complex neural interactions, this study represents a critical step toward more efficient and safer neural treatments.

This paper“An 8-Channel High-Voltage Neural Stimulation IC Design with Exponential Waveform Output” was published in Neuroelectronics. 

Liu X, Lu Z, Li J, Zhao X, Zheng L, et al. An 8-channel high-voltage neural stimulation IC design with exponential waveform output. Neuroelectronics 2024(1):0001, https://doi.org/10.55092/neuroelectronics20240001.