Microfluidic assembly of photonic colloidal structures

Over the last three decades, colloidal photonic structures have attracted intense interest because of their unique light manipulation properties. These distinct light manipulation characteristics, combined with the potential applications in novel optical devices, have promoted the development of colloidal photonic structure materials in many practical applications, including the fields of photonics, optics, optoelectronics, displays, biological analysis, and organ-on-a-chip. Therefore, the preparation of colloidal photonic structures with desired features and functions is worth investigating, particularly in industrial scale. After decades of development, microfluidic has emerged as a powerful tool in the fields of chemosynthesis, bioanalysis, drug development, organ-on-a-chip, and especially in materials preparation. With a well-designed microfluidic system, colloidal photonic structures with complex structures, controllable properties, and functions can be achieved. In this article, research progress on colloidal photonic structures derived from microfluidic assembly is discussed. Microfluidic techniques and parameters that affect the self-assemble process are first outlined. Then, the overall review on colloidal photonic structures synthesized via microfluidic assembly is presented, containing spherical and non-spherical colloidal photonic structures. After that, applications of microfluidic assembled colloidal photonic structures are listed, with emphasis on the field of biomedical engineering, such as bioanalysis, cell culture, and organ-on-a-chips. Finally, the current status, challenges, and outlook for future development are summarized