Microfluidic production of biopolymer microcapsules with controlled morphology

J Am Chem Soc. 2006 Sep 20;128(37):12205-10. doi: 10.1021/ja0635682.


We report a microfluidic approach to generating capsules of biopolymer hydrogels. Droplets of an aqueous solution of a biopolymer were emulsified in an organic phase comprising a cross-linking agent. Polymer gelation was achieved in situ (on a microfluidic chip) by diffusion-controlled ionic cross-linking of the biopolymer, following the transfer of the cross-linking agent from the continuous phase to the droplets. Gelation was quenched by collecting particles in a large pool of cross-linking agent-free liquid. The structure of microgels (from capsules to gradient microgels to particles with a uniform structure) was controlled by varying the time of residence of droplets on the microfluidic chip and the concentration of the cross-linking agent in the continuous phase. We demonstrated the encapsulation of a controlled number of polystyrene beads in the microgel capsules. The described approach was applied to the preparation of capsules of several polysaccharides such as alginate, kappa-carrageenan, and carboxymethylcellulose.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Capsules
  • Hydrogels / chemical synthesis
  • Hydrogels / chemistry*
  • Microfluidics / methods*
  • Microscopy, Atomic Force
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Polysaccharides / chemical synthesis
  • Polysaccharides / chemistry*
  • Polystyrenes / chemistry*


  • Capsules
  • Hydrogels
  • Polysaccharides
  • Polystyrenes