Recent progress of electroactive interface in neural engineering

Abstract

Neural tissue is an electrical responsible organ. The electricity plays a vital role in the growth and development of nerve tissue, as well as the repairing after diseases. The interface between the nervous system and external device for information transmission is called neural electroactive interface. With the development of new materials and fabrication technologies, more and more new types of neural interfaces are developed and the interfaces can play crucial roles in treating many debilitating diseases such as paralysis, blindness, deafness, epilepsy, and Parkinson's disease. Neural interfaces are developing toward flexibility, miniaturization, biocompatibility, and multifunctionality. This review presents the development of neural electrodes in terms of different materials for constructing electroactive neural interfaces, especially focus on the piezoelectric materials‐based indirect neuromodulation due to their features of wireless control, excellent effect, and good biocompatibility. We discussed the challenges we need to consider before the application of these new interfaces in clinical practice. The perspectives about future directions for developing more practical electroactive interface in neural engineering are also discussed in this review. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement

Materials and Structural Designs for Neural Interfaces

“…Pt, gold (Au), iridium (Ir), and indium tin oxide are the most used materials for neural interfaces due to their biocompatibility and corrosion stability to fluid . However, their intrinsic impedance causes the acquisition of neural signals with a low SNR.…”

“…Second is a faradaic charge transfer based on electrochemical reactions with direct charge transfer, such as oxidation and reduction at the tissue-electrode interface (Figure 1g). 27,28 Capacitive charge transfer occurs based on a simple electrical capacitor called an EDL capacitor as a high-dielectric constant oxide. This capacitor is formed due to the redistribution of ions at the tissue−electrode interface.…”

“…Pt, gold (Au), iridium (Ir), and indium tin oxide are the most used materials for neural interfaces due to their biocompatibility and corrosion stability to fluid. 28 However, their intrinsic impedance causes the acquisition of neural signals with a low SNR. The most persuasive strategies to overcome this electrochemical limitation include increasing the contact areas of the electrode while maintaining the size of the electrode.…”

“…First is a capacitive charge transfer based on the charging/discharging of EDL without direct charge transfer at the tissue–electrode interface (Figure f). Second is a faradaic charge transfer based on electrochemical reactions with direct charge transfer, such as oxidation and reduction at the tissue-electrode interface (Figure g). , …”

“…Likewise, CSC is a factor that represents the amount of charge stored in a neural stimulation electrode . Since the size and materials of the electrodes used in the neural stimulation are limited, it is essential to have an improved CSC.…”