Fraunhofer Institute for Applied Polymer Research (IAP) and NMI Natural and Medical Sciences Institute have jointly developed a patent-pending biomimetic tissue substitute that uses 3D printing as its structural backbone, and is now ready for industrial translation.
The material, developed under the PolyKARD project, addresses one of biomedical engineering’s most persistent challenges: replicating the nonlinear mechanical behavior of natural tissue. Structures like the pericardium flex under light load and stiffen sharply under pressure, a response conventional polymers can approximate at one end, but not both. This new multilayer design does both.
Structure as the Solution: How the Material Works
The tissue substitute is built from three distinct layers at Fraunhofer IAP’s Potsdam Science Park, each contributing a specific function. A dense polyurethane acrylate polymer film forms the base. On top of it, a wavy metastructure is deposited via 3D printing. and this is the layer that governs mechanical behavior. As the material is stretched, the waves elongate, keeping the structure pliable. Beyond a defined strain threshold, stiffness increases sharply, closely mirroring the nonlinear stress-strain response of natural pericardial tissue.
The third layer is electrospun collagen, produced through a proprietary process developed at the NMI. Its quality is continuously monitored using specialized enzymatic and non-invasive spectroscopic analyses, ensuring the biological interface meets the standard required for cell interaction.
Studies with human skin fibroblasts and epithelial cells confirmed that the fiber network’s three-dimensional morphology actively supports cell adhesion and growth, while cytotoxicity testing revealed no adverse cellular effects.
“The results show that technical materials and biological functionality can be specifically engineered and combined into biomimetic materials,” says Dr. Hanna Hartmann from the NMI. “This opens up new possibilities for the development of biohybrid implants. That is why we have now jointly filed a patent for this tissue substitute.”
From Pericardium to Platform: Broad Application Potential
While the pericardium served as the primary reference tissue for this development, the material concept is not application-specific. The same multilayer architecture, tunable metastructure, polymer base, bioactive surface, can be adapted for artificial blood vessels, stent grafts, dura mater substitutes, and artificial skin. For medical device companies, this represents a configurable platform rather than a single implant solution.
“Our development has reached a stage where it can be translated into concrete applications,” explains Dr. Wolfdietrich Meyer. “The next step is to collaborate with industrial partners to realize specific products and bring them to market-ready applications.”
The Long Search for Tissue That Behaves Like Tissue
Replicating soft tissue mechanics in 3D printed materials has been an active research front for years. Most approaches address biological compatibility or geometric customization in isolation, but matching the nonlinear mechanical signature of natural tissue, where flexibility and stiffness coexist across different strain ranges, has proven far more elusive.
For instance, research from Texas A&M University‘s Department of Biomedical Engineering identified that conventional hydrogels used in bioprinting lack sufficient structural stability and tissue-specific functions, and that ideal bioinks must simultaneously extrude into stable 3D structures, protect cells during printing, and provide an environment that can remodel into the target tissue, a combination no standard formulation had achieved.
That gap between material and biology, however, is increasingly being closed through geometry rather than chemistry. At the University of Minnesota, researchers demonstrated that by controlling filament geometry at the voxel scale, adjusting print-line height and spacing, they could tune stiffness ratios to match real human tissue, achieving anisotropy comparable to skin without changing the base material.
The Fraunhofer IAP and NMI approach lands directly in this context. By embedding the stiffening response into the printed wavy metastructure rather than the polymer itself, the team effectively decouples mechanical behavior from material choice, making the design logic transferable across tissue types and applications without reformulating from scratch.
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Featured image shows the material consists of three layers: a polymer film made of polyurethane acrylate, a 3D printed wavy metastructure, and electrospun collagen. Photo via Fraunhofer Institute.
