Microfluidic Brain‐on‐a‐Chip: From Key Technology to System Integration and Application

As an ideal in vitro model, brain‐on‐chip (BoC) is an important tool to comprehensively elucidate brain characteristics. However, the in vitro model for the definition scope of BoC has not been universally recognized. In this review, BoC is divided into brain cells‐on‐a‐ chip, brain slices‐on‐a‐chip, and brain organoids‐on‐a‐chip according to the type of culture on the chip. Although these three microfluidic BoCs are constructed in different ways, they all use microfluidic chips as carrier tools. This method can better meet the needs of maintaining high culture activity on a chip for a long time. Moreover, BoC has successfully integrated cell biology, the biological material platform technology of microenvironment on a chip, manufacturing technology, online detection technology on a chip, and so on, enabling the chip to present structural diversity and high compatibility to meet different experimental needs and expand the scope of applications. Here, the relevant core technologies, challenges, and future development trends of BoC are summarized. Somatic cells contributed by donors (human, rodent, primate) can be reprogrammed into induced pluripotent stem cells or neurons, and brain tissue/slice directly extracted from donors can be used as culture on a chip. The entire stage of neural development can be demonstrated on a chip.