The stereolithography (SLA) process and its methods are introduced in this chapter. After establishing SLA as pertaining to the high-resolution but also high-cost spectrum of the 3D printing technologies, different classifications of SLA processes are presented. Laserbased SLA and digital light processing (DLP), as well as their specialized techniques such as two-photon polymerization (TPP) or continuous liquid interface production (CLIP) are discussed and analyzed for their advantages and shortcomings. Prerequisites of SLA resins and the most common resin compositions are discussed. Furthermore, printable materials and their applications are briefly reviewed, and insight into commercially available SLA systems is given. Finally, an outlook highlighting challenges within the SLA process and propositions to resolve these are offered.

Bone regeneration requires porous and mechanically stable scaffolds to support tissue integration and angiogenesis, which is essential for bone tissue regeneration. With the advent of additive manufacturing processes, production of complex porous architectures has become feasible. However, a balance has to be sorted between the porous architecture and mechanical stability, which facilitates bone regeneration for load bearing applications. The current study evaluates the use of high resolution digital light processing (DLP) -based additive manufacturing to produce complex but mechanical stable scaffolds based on β-tricalcium phosphate (β-TCP) for bone regeneration. Four different geometries: a rectilinear Grid, a hexagonal Kagome, a Schwarz primitive, and a hollow Schwarz architecture are designed with 400 μm pores and 75 or 50 vol% porosity. However, after initial screening for design stability and mechanical properties, only the rectilinear Grid structure, and the hexagonal Kagome structure are found to be reproducible and showed higher mechanical properties. Micro computed tomography (μ-CT) analysis shows <2 vol% error in porosity and <6% relative deviation of average pore sizes for the Grid structures. At 50 vol% porosity, this architecture also has the highest compressive strength of 44.7 MPa (Weibull modulus is 5.28), while bulk specimens reach 235 ± 37 MPa. To evaluate suitability of 3D scaffolds produced by DLP methods for bone regeneration, scaffolds were cultured with murine preosteoblastic MC3T3-E1 cells. Short term study showed cell growth over 14 d, with more than two-fold increase of alkaline phosphatase (ALP) activity compared to cells on 2D tissue culture plastic. Collagen deposition was increased by a factor of 1.5–2 when compared to the 2D controls. This confirms retention of biocompatible and osteo-inductive properties of β-TCP following the DLP process. This study has implications for designing of the high resolution porous scaffolds for bone regenerative applications and contributes to understanding of DLP based additive manufacturing process for medical applications.

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Functional 3D components such as perfusion channels and mechanical actuation elements at cellular length scales can support cell survival and tissue maturation in tissue modeling devices. These advanced requirements call for increasingly complex materials and 3D fabrication methods. Here, a high‐resolution dual‐material 3D printing concept is developed, where distinct materials are produced locally by orthogonal chemical reactions depending on the illumination wavelength. A tough, stiff epoxy network results from cationic polymerization in UV light, while a soft and diffusion‐open hydrogel forms by free‐radical polymerization initiated by blue light. Thus, dual‐exposure allows for selection of material properties in every voxel, while retaining the 3D design flexibility associated with stereolithography. This enables single‐process fabrication of devices integrating mechanically stable chip‐to‐world interconnects and compliant, diffusion‐open perfusable channel components of 150 µm in width and height, while also allowing structural and mechanical feature dimensions down to 60 µm. A perfusion chip capable of creating a stable uniaxial chemical gradient by passive dye diffusion through hydrogel sections, and a negative Poisson ratio structure based on the interplay between stiff rotators and compliant hinges, are manufactured as proof‐of‐concept microdevices. Lastly, week‐long culture of hydrogel‐encapsulated human liver cells demonstrates the cytocompatibility of both materials.