Researchers develop new materials for brain-computer interfaces

Recently, the flexible electronics research team led by Professor Lan Wei of the School of Physical Science and Technology of Lanzhou University has developed a capacitive ion diode based on molybdenum oxide electrode, and the related results were published in the international journal Advanced Materials with the title of “Biocompatible Supercapacitor Diode with Enhanced Rectification Ability for Ion/Electronic Coupled Logic Operations”.

Molybdenum oxide-based capacitive ion diode for human-computer interaction Photo courtesy of the research group

In recent years, brain-computer interface technology has developed rapidly, but there is still a certain gap in the practical level of two-way communication distance between the human brain and the computer, which is mainly due to the fact that the human brain and the computer use two different signal transmission media, ion and electron, respectively. Ion-electron coupling devices can realize the organic combination of ion transport and electron transfer in the same circuit, thus providing a possible medium for information transfer between biological systems and electronic devices. However, in order to truly realize the information interaction between biological systems and electronic devices, it is also necessary to design and develop devices with logic computing functions to complete the transmission, processing and feedback of information. Capacitive ion diode (CAPode) is a new class of electrochemical functional devices based on supercapacitors, which is considered to be the most promising basic component for building ion-electron coupling circuits. However, the current research of capacitive ion diodes is still in its infancy, limited to some problems of electrode materials and electrolytes themselves, existing capacitive ion diodes still have the problems of low rectification ratio (~10), low specific capacitance (< 80F g-1), poor stability, poor biocompatibility and high manufacturing cost, which cannot meet the practical requirements.

Due to the dense two-dimensional layered crystal structure and negatively charged interlaminar ion transport channel of molybdenum oxide material, the molybdenum oxide electrode exhibits a double ion screening effect of size and charge on electrolyte anions and cations. This unique synergistic ion sieving effect allows the molybdenum oxide working electrode to exhibit an ultra-high rectification ratio of 136, which is an order of magnitude higher than existing systems. At the same time, combined with the charge storage mechanism of intercalated pseudocapacitance and the optimally matched electrolyte system, the molybdenum oxide electrode exhibits a high specific capacitance of 448 F g-1 and excellent cycle stability of up to 20,000 cycles. Such excellent rectification characteristics and electrochemical performance enable the capacitive ion diode to work efficiently and stably in two types of logic operation circuits: AND and AND. In addition, molybdenum oxide and related component materials have good biocompatibility, which makes the constructed capacitive ion diode show great potential in the field of brain-computer interface based on ion-electron coupling circuit in the future. (Source: China Science News, Wen Caifei, Faisha)

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