Facile and scalable generation of fluorescent microspheres using a microfluidic electrojetting device

Facile and scalable approaches for preparing fluorescent microspheres are indispensable tools in material science due to their immense potential for reducing the tedious conditional trial-and-error experiments for every single material. In this study, we propose a microfluidic method based on oscillating electric field (OEF)-induced electrojetting to fabricate size-controllable fluorescent microspheres embedded with various fluorescent substances. Briefly, an oscillating electric field is used to manipulate the size and productivity of highly uniform droplets; the size of droplets can be adjusted by simply varying the intensity and frequency of the electric field over a range of near three orders of magnitude. Subsequently, ultraviolet (UV) irradiation is used to solidify the droplets to fabricate fluorescent microspheres. To demonstrate the universality of the proposed method in different types of fluorescent substances, we use fluorescein sodium (FS), green fluorescent protein (GFP), and CdTe quantum dots (QDs) to synthesize fluorescent microspheres. The prepared microspheres show narrow size distribution (average coefficient of variation below 2.1%) and intense fluorescence emission. Overall, the proposed method is a novel and facile approach for synthesizing fluorescent microspheres, showing great promise for the preparation of polymer, functionalized and other materials with potential applications in various fields of biomaterials and biochemical assays.