Johannes Homa

Lithography-based ceramic manufacture (LCM) of auxetic structures: present capabilities and challenges

Auxetic metamaterials are known for having a negative Poissons ratio (NPR) and for displaying the unexpected properties of lateral expansion when stretched and densification when compressed. Even though a wide set of micro-manufacturing resources have been used for the development of auxetic metamaterials and related devices, additional precision and an extension to other families of materials is needed for their industrial expansion. In addition, their manufacture using ceramic materials is still challenging. In this study we present a very promising approach for the development of auxetic metamaterials and devices based on the use of lithography-based ceramic manufacturing. The process stands out for its precision and complex three-dimensional geometries attainable, without the need of supporting structures, and for enabling the manufacture of ceramic auxetics with their geometry controlled from the design stage with micrometric precision. To our knowledge it represents the first example of application of this technology to the manufacture of auxetic geometries using ceramic materials. We have used a special three-dimensional auxetic design whose remarkable NPR has been previously highlighted.

Lithography-Based Ceramic Manufacturing: A Novel Technique for Additive Manufacturing of High-Performance Ceramics

Albeit widely established in plastic and metal industry, additive manufacturing technologies are still a rare sight in the field of ceramic manufacturing. This is mainly due to the requirements for high performance ceramic parts, which no additive manufacturing process was able to meet to date.The Lithography-based Ceramic Manufacturing (LCM)-technology which enables the production of dense and precise ceramic parts by using a photocurable ceramic suspension that is hardened via a photolithographic process. This new technology not only provides very high accuracy, it also reaches high densities for the sintered parts. In the case of alumina a relative density of over 99.4 % and a 4-point-bending strength of almost 430 MPa were realized. Thus, the achievable properties are similar to conventional manufacturing methods, making the LCM-technology an interesting complement for the ceramic industry.

Tissue Engineering Scaffolds for Bone Repair: General Aspects

Hard tissue repair is a very relevant and challenging area for the emerging fields of tissue engineering and biofabrication due to the very complex three-dimensional structure of bones, which typically include important variations of porosities and related mechanical properties. The need of porous and rigid extra cellular matrices, of structural integrity, of functional gradients of mechanical properties and density, among other requirements, has led to the development of several families of biomaterials and scaffolds for the repair and regeneration of hard tissues, although a perfect solution has not yet been found. Further research is needed to address the advantages of different technologies and materials for manufacturing enhanced, even personalized, scaffolds for tissue engineering studies and extra cellular matrices with outer geometries defined as implants for tissue repair, as the niche composition and 3D structure play an important role in stem cells state and fate. The combined employment of computer-aided design, engineering and manufacturing (also CAD-CAE-CAM) resources, together with rapid prototyping procedures, working on the basis of additive manufacturing approaches, allows for the efficient development of knowledge-based functionally graded scaffolds for hard tissue repair in a wide range of materials and following biomimetic approaches. In this chapter we present some design and manufacturing strategies for the development of knowledge-based functionally graded tissue engineering scaffolds aimed at hard tissue repair. A complete case of study, linked to the development of a scaffold for tibial repair is also detailed to illustrate the proposed strategies.