Mass transfer strategies for MicroLED chip assembly: pick-and-place techniques and fluidic self-assembly methods

Micro light-emitting diode (MicroLED) displays possess exceptional advantages including rapid response speed, autonomous light emission, high contrast, and long service life. The technology is emerging alongside rapid advancements in wearable devices, virtual reality, augmented reality, and TV displays. Due to these strengths, MicroLED displays are widely recognized as the most disruptive and revolutionary next-generation display technology. However, the miniaturized characteristic of MicroLED chips poses significant challenges for efficiently, accurately, and cost-effectively transferring millions of these chips from the donor substrate to the receiver substrate. Over the past two decades, numerous innovative mass transfer strategies have been developed. These strategies aim to overcome the limitations of traditional transfer techniques. Such advancements are driving the commercialization of MicroLED displays. Herein, we review the development of mass transfer strategies for MicroLED chips and classify these strategies into two primary categories: pick-and-place technique and fluidic self-assembly method. The former is further classified based on different adhesion modulation mechanisms, while the latter is classified based on different driving forces. Furthermore, this review provides an in-depth analysis of the working mechanisms, along with a comprehensive evaluation of the advantages and disadvantages associated with specific strategies.