FIGURE 3.

Gelation triggered by different calcium complexes. (A,B) Effect of water–oil flow rate ratio (Q_aqu/Q_oil) and acetic acid concentration on the formation of alginate microgels when (A) Ca-NTA and (B) Ca-EDTA were used as the crosslinker, respectively. White and black areas indicated complete crosslink and uncrosslink, respectively. If the gelation process can be achieved on-chip, solid-like hydrogel particles can be obtained. Otherwise, only liquid can be collected since the gelation of the droplets cannot be realized within the short time window, for which we considered them as uncrosslinked microgels. (C) Gelation time in different acid concentrations where Ca²⁺ ions were chelated in NTA or EDTA. (D) AutoCAD design of the microfluidic device for cell encapsulation. (E,F) Microscopic images of microchannels (E) for formation of alginate cell-laden microgels (F). White arrows indicate cells. (G,H) Effect of Ca-NTA on microgel size and cell distribution. (G) Size distribution of alginate microgels. (H) Cell distribution in the microgels follows the Poisson distribution. Scale bar is 100 μm (***p < 0.001).