Active devices and systems for closed-loop neuromodulation.

Neuromodulation has become a central topic in neuroscience and biomedical engineering, as it provides powerful means to interrogate and regulate neural activity and offers promising therapeutic strategies for a wide range of neurological disorders. Conventional neuromodulation approaches predominantly rely on electrode-based electrical stimulation or remote physical stimuli, including optical, chemical, magnetic, and ultrasound-based methods, to influence neuronal excitability and neural circuit dynamics. Recent advances in neuromodulation involve microsystem engineering, nanotechnology, and genetically enabled techniques such as optogenetics. They have achieved increasingly precise and versatile control over neural systems with high spatial and temporal resolution. Owing to their intrinsic capability for integrated sensing, signal amplification, and adaptive regulation, active devices are particularly well suited for system-level implementations of neuromodulation. This review summarizes recent advances in active devices for neuromodulation, with a particular emphasis on their functional roles in neural regulation. By discussing different material platforms and device architectures, this review further provides insights into the rational design of next-generation neural interface systems.