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. 2022 Sep 15;122(22):16839–16909. doi: 10.1021/acs.chemrev.1c00798

Figure 2.

Figure 2

The variety of microgel structures for N = 2. We classify the structures in terms of overall topology (“engulfing” vs “Janus”) and dimensionality (0D, 1D, 2D, 3D) for the case of two (N = 2) different hydrogel phases A and B (or a hydrogel and another immiscible phase such as oil or gas) suspended in the external phase C (typically cell culture medium). (A) (a–c) pNIPAAM core–shell beads. Scale bars 100 μm. Adapted with permission from ref (63). Copyright 2010 American Chemical Society. (d–f) ETPTA, gelatin, and alginate–chitosan porous beads, respectively. Scale bars 200 μm. Adapted with permission from refs (64−66), respectively. Copyright 2015 American Chemical Society, 2013 Wiley, and 2018 Wiley, respectively. (g–h) Cross-sectional view of alginate core–shell fibers and hollow fibers, respectively. Scale bars 200 μm. Adapted with permission from ref (67). Copyright 2018 Nature Publishing Group. (i) Alginate fibers engulfing aqueous droplets. Scale bar 300 μm. Adapted with permission from ref (68). Copyright 2021 American Chemical Society. (j) Cross-section of an alginate ribbon with multiple hollow cores. Scale bar 100 μm. Adapted with permission from ref (69). Copyright 2016 Wiley. (k) Alginate sheet. Scale bar 2 mm. Adapted with permission from ref (70). Copyright 2018 Royal Society of Chemistry. (l) Fluorescent alginate sheet. Scale bar 500 μm. Adapted with permission from ref (59). Copyright 2012 Wiley. (m) Porous alginate membrane. Scale bar 100 μm. Adapted with permission from ref (71). Copyright 2016 American Chemical Society. (n) Close-packed norbornene-modified hyaluronic acid (NorHA) microbeads suspended in PBS. Scale bar 200 μm. Adapted with permission from ref (72). Copyright 2019 Wiley. (o) Porous gelatin scaffold with gradient in pore size. Scale bar 500 μm. Adapted with permission from ref (54). Copyright 2019 Wiley. (p) Extrusion 3D-printed alginate fibers. Scale bar 500 μm. Adapted with permission from ref (73). Copyright 2017 Elsevier. (q) Cross-section of wet-spun cell-laden alginate fibers. Scale bar 50 μm. Adapted with permission from ref (74). Copyright 2018 Elsevier. (B) (a–d) Alginate beads. Scale bars 500, 100, 200, and 200 μm, respectively. Adapted with permission from refs (75−78), respectively. Copyright 2015 Royal Society of Chemistry, 2018 Wiley, 2013 American Institute of Physics, and 2020 Wiley, respectively. (e–g) Alginate Janus fibers. Scale bars 200 μm. Adapted with permission from ref (79 and 80). Copyright 2020 Wiley and 2014 Wiley. (h) GelMa fiber. Scale bar 1 mm. Adapted with permission from ref (81). Copyright 2019 The Royal Society of Chemistry. (i) Alginate fiber. Scale bar 800 μm. Adapted with permission from ref (82). Copyright 2011 Nature Publishing Group. (j,k) Alginate sheets. Scale bars 500 μm. Adapted with permission from refs (59 and 83), respectively. Copyright 2012 Wiley and 2013 Elsevier, respectively. (l) Granular sheet made of GelMa microrods arranged into a macroscale stripe pattern. Scale bar 2 mm. Adapted with permission from ref (84). Copyright 2017 Wiley. (m) pNIPAAM granular sheet. Scale bar 500 μm. Adapted with permission from ref (85). Copyright 2020 Nature. (n,o) Aginate and PEGDA sheets, respectively. Scale bars 500 μm. Adapted with permission from refs (59, 86, and 87), respectively. Copyright 2012 Wiley and 2016 American Association for the Advancement of Science. (p) 3D scaffold made of annealed PEG beads. Scale bar 200 μm. Adapted with permission from ref (50). Copyright 2019 Wiley. (q) 3D-printed hydrogel droplets stabilized by lipids. Scale bar 100 μm. Adapted with permission from ref (88). Copyright 2021 The Authors. (r) Rolled alginate sheet. Scale bar 500 μm. Adapted with permission from ref (59). Copyright 2012 Wiley. (s) Stacked alginate sheets. Scale bar 500 μm. Adapted with permission from ref (59). Copyright 2012 Wiley.