In recent years, stimuli-responsive hydrogels have gained tremendous interest in designing complex smart 4D materials for applications ranging from biomedicine to soft electronics that can change their properties on demand over time. However, at present, a hydrogel’s response is often induced by merely a single stimulus, restricting its broader applicability. The controlled hierarchical assembly of various hydrogel building blocks, each with a tailored set of mechanical and physicochemical properties as well as programmed stimulus response, may potentially enable the design and fabrication of multi-responsive polymer parts that process complex operations, like signal routing dependent on different stimuli. Since inter-connection stability of such building blocks directly accompanies the transmission of information across building blocks and is as important as the building property itself to create complex 4D materials, we provide a study on the utility of an inter-crosslinking mechanism based on UV-induced 2,3-dimethylmaleimide (DMMI) dimerization to inter-connect acrylamide-based and N-isopropylacrylamide-based millimeter-sized cubic building blocks, respectively. The resulting dual-crosslinked assemblies are freestanding and stable against contraction–expansion cycles in solution. In addition, the approach is also applicable for connecting microfluidically fabricated, micrometer-sized hydrogel spheres, with the resulting assemblies being processable and mechanical stable, likewise resisting contraction–expansion in different solvents, for instance.

The soft colloidal probe (SCP) assay is a highly versatile sensing principle employing micrometer-sized hydrogel particles as optomechanical transducer elements. We report the synthesis, optimization, and conjugation of SCPs with...

Controlled electrocoalescence of droplet pairs containing fast-gelling hydrogel precursors is highlighted as a versatile method for processing reactive species into well-defined uniform microgels as well as a special type of anisotropic microgels with a tunable curvature via droplet microfluidics.

With the rise of particle‐based material systems in life and materials sciences over the past years, high‐throughput microfluidics has gained tremendous interest as a simple fabrication method for large quantities of tailored emulsions and microparticles. Here, we present the fabrication of microfluidic systems that combine parallelized droplet formation with sequential droplet splitting by 3D printing via projection‐microstereolithography for large‐scale production of water‐in‐oil emulsions and polymer microparticles. The process of droplet splitting is investigated in a 3D‐printed single‐channel, flow‐focusing device and then integrated into a microfluidic system with N = 3 × 20 parallelized channels with individual channel cross‐sections of 60 μm. The arrangement of the integrated functional microfluidic elements is evaluated for different orientations to the 3D printing direction. Furthermore, emulsion droplet size adjustment for flow‐focused and parallelized microfluidic systems is studied. For a proof‐of‐concept, the 3D‐printed microfluidic system is used to fabricate water‐in‐oil emulsions and fluorescently labeled, thermally crosslinked poly(acrylamide) microparticles. With that, our platform provides a straightforward and time‐efficient path toward microgel production in the size range of 140–170 μm on a milliliter‐per‐hour scale combining droplet formation parallelization and three integrated droplet splitting stages.