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Table 5 External gelation with off-chip introduction of cross-linkers

From: Preparation of alginate hydrogel microparticles by gelation introducing cross-linkers using droplet-based microfluidics: a review of methods

References Hu et al., 2012 [20] Zhang et al., 2020 [59] Present review
Droplet generation Na-alginate 1.5 wt% 0.006–1 wt% 0.006–1 wt%
Continuous fluid N-decanol DMCa DMCa
Use of surfactant Span 80 NO NO
Geometry Flow-focusing Cross-flowing Cross-flowing
Microfluidic material Glass chip Fluoropolymer tubing and junctions Fluoropolymer tubing and junctions
External gelation by introducing Na-alginate and cross-linkers off-chip during collection Number of phases or steps 2 phases - 1 collection bath 1 phase - 1 collection bath 2 phases - 2 successive collection baths
Description of phases or steps Phase 1 CaCl2 (15 wt%) in n-decanol CaCl2
(0.1–1 wt%)
Step 1 DMC and evaporation of DMC
Phase 2 Ba (CH3COO)2 (15 wt%)
in water and glycerol
Step 2 CaCl2 (0.5–10 wt%) in water
Surfactant Span 80 NO NO
  1. aContinuous and dispersed fluids partially miscible