LAUSR

Abstract Aqueous microdroplets are of significant interest in biological fields, while the employment of water-in-oil (w/o) emulsion and lack of spatial control precluded its widespread application. Herein a novel microfluidic approach is developed to generate water-in-water (w/w) microdroplets embedded in hydrogel microfibers. Aqueous two phase system (ATPS) is applied to generate w/w droplets, and alginate is introduced to continuous phase to form microfibers, which offers spatial restriction and manipulation possibility to droplets. The size and pattern of aqueous droplets can be precisely controlled, and immobilization within hydrogel fiber facilitates easy manipulation and observation. The microdroplets surrounded by hydrophilic environment can act as a cell-cell interaction model, and their potential for biological and environmental applications are demonstrated by long-term culture of encapsulated cells and water remediation of Bacillus subtilis.