3D-Printed, Bioinspired and Tunable Strain-Stiffening Structures as a Candidate for Cell Studies and Tissue Engineering

2-photon-polymerization (2PP) based 3D printing is a technique that enables the fabrication of highly complex micro- and nanostructures with high spatial control in all three dimensions. Therefore, 2PP direct laser writing gives rise to structures mimicking the microenvironment of cells and their extracellular matrix (ECM), which is highly interesting for the field of cell studies, tissue engineering and biomedical applications.<br/>One very important property of cells, ECM and soft tissues like tendons, skin, muscles or ligaments is the nonlinear strain-stiffening behavior: They become stiffer with an increasing strain, leading to a J-shaped curve in the stress-strain diagram. We mimicked this mechanical phenomenon by developing a metamaterial, that increases its stiffness at a certain strain rate by simple design features. The obtained structure has a highly nonlinear, adjustable, rate-independent and reversible strain-stiffening behavior that can be implemented into various elastic materials and hence is not material depended. Changes in geometry affect the point of stiffening as well as the initial and final stiffness of the material. In addition, the strain-stiffening mechanics can also be used in complex three-dimensional arrangements like sheets, tubes or 3D networks. [1]<br/>In this work, we now study the miniaturization of our metamaterial. Using 2PP direct laser writing with different materials ranging from hydrogels to acrylate-based materials and silicones, allows us to study our design in the micron range. We evaluate the 3D printed structures in the means of shape accuracy, size limitations, force range and their stability in 3D. Materials, which we found very promising are hydrogels and highly elastic resins. By using materials which moreover allow cell adhesion, the behavior of cells can be studied. In future, our design will be used to study the mechanosensing and mechanotransduction of cells in a 3D network, that truly resembles the mechanics of soft tissue and the ECM.<br/><br/>References:<br/>1. Taale, M.; Schmidt, M.; Taheri, F.; Timmermann, M.; Selhuber-Unkel, C. A Minimalistic, Synthetic Cell-Inspired Metamaterial for Enabling Reversible Strain-Stiffening. Advanced Materials Technologies 2023, 8 (11). https://doi.org/10.1002/admt.202201441.