Rotary Structural Color Spindles from Droplet Confined Magnetic Self-Assembly

Structural colors materials are profoundly explored owing to their fantastic optical properties and widespread applications. Development of structural color materials bearing flexible morphologies and versatile functionalities is highly anticipated. Here, a droplet-confined, magnetic-induced self-assembly strategy for generating rotary structural color spindles (SCSPs) by fast solvent extraction is proposed. The as-prepared SCSPs exhibit an orderly close-packed lattice structure, thus appearing brilliant structural colors that serve as encoding tags for multiplexed bioassays. Besides, benefitting from the abundant specific surface area, biomarkers can be labeled on the SCSPs with high efficiency for specific detection of analytes in clinical samples. Moreover, the directional magnetic moment arrangement enables contactless magnetic manipulation of the SCSPs, and the resultant rotary motions of the SCSPs generates turbulence in the detection solution, thus significantly improving the detection efficiency and shortening the detection time. Based on these merits, a portable point-of-care-testing strip integrating the rotary SCSPs is further constructed and the capability and advantages of this platform for multiplexed detection of tumor-related exosomes in clinical samples are demonstrated. This study offers a new way for the control of bottom-up self-assembly and extends the configuration and application values of colloidal crystal structural colors materials.