Fig. 1. Schematic diagram of neural probe using laser as light source, optical fiber as optical signal transmission channel, and metal electrode wire as electrical signal channel^[18]

Fig. 2. Schematic illustration of the fabrication of integrated probe. (a) Design of prefabricated bars for composite materials^[34]; (b) schematic diagram of hot stretching process principle^[35]; (c) preparation of a typical hydrogel probes^[34]; (d) schematic diagram of femtosecond laser micromachining process^[36]

Fig. 3. Schematic diagram of the multifunctional probe prefabrication and the application of a living mouse. (a) Schematic diagram of fabrication of optical fiber probe precast; (b) electrophysiological signals at 2 days, 1 week, 1 month, and 2 months after the probe was implanted in the mPFC of mice and subjected to synchronous photogenetic stimulation^[27]

Fig. 4. Schematic diagram of the preparation of an all-polymer neural probe and its good biocompatibility.(a) Fabrication and thermal stretching of prefabricated rods including recording electrodes, optical waveguides, and microfluidic channels; (b) confocal microscope images of glial scar formation and blood-brain barrier breach around the implanted probe and stainless steel microwires at 1 month respectively (scale bar is100 μm)^[37]

Fig. 5. The adaptive bending stiffness of hydrogel hybrid probes and its high matching with mechanical properties of nerve tissue. (a) Description of the concept of adaptive bending stiffness; (b) Mises stress distribution of stainless steel, silica, PC fibers, and hydrogel hybrid probes in brain tissue during lateral micromotion^[34]

Fig. 6. Schematic diagram of the design of LOEF and the demonstration of its light leakage. (a) Three functions of LOEF; (b) schematic diagram of the principle of light leakage by laser ablation of the micro-window; (c) different light leak intensity from a pattern of a single, 1×10, and 2×10 micro-windows (from right to left); (d) image of fluorescent nanobeads in gelatin surrounding the LOEF showing the spatial distribution of light leak^[30]

Fig. 7. Schematic diagram of the multifunctional neural probe to simplify optogenetic experiments. (a) Schematic comparison of two-step operation performed by photogenetic experiment and one-step operation performed by multifunctional fiber probe; (b) schematic illustration of simultaneous viral delivery, optical stimulation and electrical recording in mPFC of mice with fiber probe; (c) integration of fiber probe photoelectric function with microfluidic channels^[34,37]