The progress significantly beyond the state-of-the-art concerns:
- 4D printed chemically crosslinked semicrystalline networks (publication n. 2). Several additive manufacturing techniques have been used for shape memory polymers. However, most 4D printing studies focus solely on irreversible shape memory effects (SME), limiting applications requiring reversible behavior. Notably, no research has explored the challenges of 4D fabrication via extrusion technology for structures with reversible two-way SME. Because of its cost-effectiveness, user-friendly nature, and wide availability of thermoplastic polymers, material extrusion can offer noteworthy advantages. We thus developed a novel 4D printing approach using extrusion technology (and in line UV crosslinking) to fabricate structures made of semi-crystalline polymer networks featuring the reversible two-way SME. These polymers are highly attractive, given their easy tailorability, excellent shape-memory performances, and fast responses to stimuli. Moreover, our systems are highly biocompatible and thus suitable for the biomedical field and, importantly, for the biological purposes of CoDe4Bio. Our achievement opens the floodgates to implement 4D printing via a cost-effective and user-friendly extrusion technology for developing dynamic structures to be used in a wide variety of applications also beyond the focus of CoDe4Bio.
- Design and manufacturing of self-folding gradient-based soft actuators (publication n. 7, awarded with an inside front cover). Using the same technology, we developed a novel approach to fabricate soft actuators based on semi-crystalline polymer networks, also proposing a theoretical model to predict bending. The proposed approach overcomes current approaches that generally rely on smart hydrogels, multiple materials, or pre-stretched systems to fabricate self-folding actuators. In fact, this approach simplifies the design and fabrication steps by achieving bending using a single material whose properties vary along the thickness of the structure. Moreover, it avoids the need for multi-material printers, adhesion issues typical of multi-material designs, limited mechanical properties of hydrogels, and additional setups for pre-stretch application.
- Development of a new approach for property tuning in semi-crystalline networks. This approach will offer a new way to optimize properties in semi-crystalline networks while avoiding relying on chemical modifications alone. We expect these experiments to provide the most comprehensive characterization of these materials.
- Flexible theoretical formulation for multi-phase semi-crystalline networks (publication n. 4). The model depicts an important contribution as the proposed formulation represents the first model with the capability to address the characterization of all crosslinked semi-crystalline polymer networks with two, or more, crystalline domains.
