Templating Techniques to Form Porous Hydrogels

Methods to create highly controlled microporous hydrogels have also recently been investigated [78-81]. This technique relies on sphere-templating — or more generally, colloidal-crystal templating — in which a monodisperse spherical porogen is assembled into a packed bed as shown in Fig. 4.4. The hydrogel precursor solution is then infused into the voids between the packed porogen. Crosslinking the hydrogel into a solid skeleton followed by removal of the porogen generates microporous hydrogels with well-defined spherical, interconnected voids that can allow passage of cells through the material. Void space is controlled by the size and shape of the porogen, while the size of interconnected pores can be controlled by sintering the porogen prior to introducing the polymer solution [82]. Sphere-templated hydrogels made of pHEMA [79, 80], PEG [81], or polyacrylamide [78] have been demonstrated using spherical porogens made from polymethylmethacrylate (PMMA) [79-81], or polystyrene [78].

Fig. 4.4 Dense packing of porogen particles creates a template structure that can be infused with a hydrogel precursor. Following crosslinking, the porogen can be dissolved to generate a hydrogel structure with highly controlled and regular pore structures. Photo courtesy of Vicki Colvin
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