Publication
Many biological materials possess well-defined structures across many length scales and exhibit combinations of mechanical properties that remain unmatched in synthetic materials. Such an example of a biological material is the marine mussel byssus, which combines functionality and processability with high toughness and stiffness. This combination of properties serves as an inspiration for the design of a wide variety of novel materials. Most synthetic materials, such as hydrogels, are fabricated in bulk, where the overall composition can be tuned. Micrometer-sized control over the composition is achieved by formulating hydrogels as granular systems. However, it remains difficult to abruptly change the composition of hydrogels on a µm or even sub-µm level. In this thesis, I establish approaches to control the composition of hydrogels on 100s of nm to a few µm length scales. This is achieved by exploiting polymer phase separation within emulsion drops and bulk hydrogels. To control the structure on the micrometer length scales, I tune the size of the microparticles. The mm-size scale structure is controlled by exploring direct ink writing (DIW)-based 3D printing. I investigate the influence of porous microgels on the overall mechanical properties of load-bearing hydrogels. I subsequently functionalize the pores with a second polymer network that can be ionically reinforced to increase the stiffness. To add functionality to the material, I produce temperature-responsive porous microfragments that can be processed into soft-responsive actuators. Last, I develop porous hydrogels utilizing a bulk approach. I functionalize the pores with a second polymer that is confined by the surrounding matrix. The osmosis-driven swelling of the resulting structured hydrogels is harnessed for their reversible strengthening and stiffening. I illustrate the applicational potential of microstructured hydrogels by using them as soft actuators. Finally, the thesis concludes with key findings and a perspective for future research advancing the field of microstructured hydrogels and their potential future applications. To summarize, I successfully fabricated microstructured hydrogels by exploiting water-based phase separations that allow local control of the structure in granular and bulk systems across multiple length scales. The work of this thesis contributes to designing the microstructure of hydrogels, thereby opening new avenues to add functionalities to them.