(174az) Flexible and Adaptable Neural Array Biosensors with Liquid Metal Microfluidic Channels

A neural array is a human-machine interface device that detects and collects neural signals, known as action potentials, generated by neurons. Implantable neural arrays are promising biosensors for accurately recording electrophysiological signals from brains. While extensive research has been conducted on neural array development, long-term implantation for disease diagnosis remains challenging because the neural array biosensors’ configurations are limited, and the conventional materials are mostly rigid. In this study, we present flexible and adaptable neural arrays using liquid metal electrodes for the first time. A flexible neural array is fabricated by two-photon 3-D printing technology, allowing for customizable designs ranging from micrometer to nanometer size. Therefore, neural arrays developed in this study can be tailored by two-photon 3D printing technology. Furthermore, gallium (Ga), a liquid at body temperature, is utilized to freely create microfluidic channels in flexible two-photon 3D-printed structures. Since gallium remains liquid and flexible at the body temperature, the entire device, after fabrication, becomes flexible upon implantation in the body. Hence, this flexibility reduces the mechanical mismatch between the tissue and the array, enabling long-term implantation and stable tracking of the neural signals. After generating microfluidic Ga channels, poly(3,4-ethylenedioxythiophene) doped with tetrafluoroborate (PEDOT:BF₄) is electrochemically deposited onto the gallium electrode surface to reduce the interfacial impedance and enhance electrochemical performances. This novel neural array device exhibits significantly improved interfacial impedance compared to the conventional neural arrays, ranging from 1 to 10 KΩ. Consequently, this novel method of the development of the customizable neural array paves the way for the advancement of next-generation human-machine interface devices. Moreover, the device’s flexibility and the results of outstanding mechanical and electrochemical performances indicate its promising application as a human-machine interface device for chronic implantation.