What chemical materials are used in the epoch-making brain-computer interface?

On February 20, American entrepreneur Musk said that after his brain-computer interface company "Neuralink" completed the first human brain device implantation surgery, the first subject "seems to have fully recovered with no adverse reactions. The subject can move the mouse on the computer screen just by thinking." This experiment is undoubtedly of great significance to mankind. By implanting electrodes, chips and other devices into the human brain, a communication and control channel connecting the human brain with external devices is established, thereby achieving the purpose of directly controlling external devices with brain bioelectric signals or regulating brain activity with external stimuli. This will provide strong guarantees for future human-computer interaction and provide new directions for solving some medical problems.

Simply put, a brain-computer interface can connect the human brain to external devices, so that neural signals can be collected by sensors and converted into electrical signals, etc., and the ideas that the brain thinks or tries can be output from electronic devices in the form of text, etc., to achieve information exchange between the brain and the machine. There are two types of brain-computer interfaces: invasive and non-invasive. Invasive means that the patient implants electrode sensors into the cerebral cortex under the skull through a craniotomy, with the skull serving as the interface location for information conversion. Non-invasive means that the sensor is attached to the outside of the patient's skull or scalp, and electrical signals are captured through stimulation and chemical sensor signals are analyzed to achieve brain-computer transmission of information.

Brain-computer interfaces enable high-throughput information exchange between the human brain and external mechanical devices. For more than 50 years, neurophysiologists and chemists have been using various electrodes and sensor materials to study brain activity, many of which are common in the field of chemical research. Now, we will briefly sort out the applications of some chemical materials in brain-computer interface technology and analyze why they have attracted attention in this field.

Carbon Nanomaterials

Carbon nanomaterials can be divided into zero-dimensional carbon materials fullerenes and nanodiamonds, one-dimensional carbon materials carbon nanotubes, and two-dimensional materials graphene. The main reason for the application of these materials in brain-computer interfaces is that carbon materials are biocompatible and non-toxic, providing superior charge injection capabilities and high conductivity, enabling high-throughput electrode interfaces to improve signal recording quality and stimulation efficiency. The lightweight, porosity, flexibility, conductivity and stability of carbon nanoframes make them useful tools for neural tissue engineering and can enhance the flexibility of electrodes. A research team at the University of Melbourne selectively deposited chemically modified nanodiamonds on carbon fiber microelectrodes as sensors for intra-brain neural stimulation, high-quality neuronal signal recording and neurotransmitter detection.

Hydrogel

Hydrogel is a typical soft and wet material with a unique three-dimensional hydrophilic network structure that is friendly to human tissue. Hydrogels are widely studied and used due to their unique mechanical properties, biocompatibility, ionic conductivity, and structural designability. Hydrogels can provide a good carrier for a variety of inorganic nanomaterials, thereby constructing composite materials with better performance. Hydrogels with good conductivity, stretchability, stimulus responsiveness, and high toughness can be used for wearable sensors, brain-computer interface electrodes, etc. By collecting and analyzing EEG signals, brain-computer interfaces provide access to a large amount of real-time brain information, including brain activity and mental state. Wang Weiwei's research team at Tianjin University has successfully developed a flexible electrode based on an elastomer-hydrogel composite that can efficiently detect EEG signals and is used in brain-computer interface research.

Organic electrochemical transistors

Organic electrochemical transistors are semiconductor materials with excellent ionic and electronic conduction properties. Ion-electron interactions make them an interactive interface between biology and electronics. They can directly sense changes in the concentration of electrons and holes generated by electrochemical reactions, thereby achieving highly sensitive signal detection. This makes it a feasible solution for building brain-computer interface systems. Peng Huisheng's team at Fudan University combined carbon nanotube fibers with organic semiconductor materials to prepare flexible, implantable fiber-shaped organic electrochemical transistors that can achieve stable detection of trace changes in chemical substances in the body and show good biocompatibility and stability. Thanks to the excellent capture of bioelectronic chemical reaction signals, the device can detect hydrogen peroxide, glucose, dopamine, glutamate, etc. in the human body, showing high sensitivity and stability. Brain immunofluorescence experiments showed that no inflammatory response was found to the device, and the safety performance was good.

Brain-computer interface is a scientific technology with epoch-making research significance, but the research risks it faces still need to be taken seriously, and the safety and device stability need to be verified over time. At present, my country's research in this field should actively keep pace with the international community, and there will be broad research space in the future.

(Mo Zunli is a professor and doctoral supervisor at Northwest Normal University, and Lv Wenbo is a master's student at Northwest Normal University)