Verowhite

An Objet30 Prime (Stratasys, Ltd., Eden Prairie, MN, USA) 3D printer was used to produce the 10 mandibular models with MJ technology. The chosen materials were a white photopolymer resin VeroWhite (Stratasys, Ltd., Eden Prairie, MN, USA) and a water-soluble support material SUP706 (Stratasys, Ltd., Eden Prairie, MN, USA). The software Objet Studio Software v. 9.2.11.6825 (Stratasys, Ltd., Eden Prairie, MN, USA) was adjusted to the following printing settings with a tray material high-speed (HS), glossy surface option and a layer thickness of 28 microns. The model was positioned in the upper left corner of the built platform. The printing time was 12 h and 14 min. Subsequently, post-processing was required to remove the water-soluble supporting structures with a WaterJet Station (Stratasys, Ltd., Eden Prairie, MN, USA).

All 3D-printed molds were designed and drawn using the computer-aided design (CAD) software, Solidworks. Each HF-like extension on the molds was 500 μm in diameter and 4 mm in length. The molds with varying hair densities (19, 81, 255 HFs per cm²) were 3D-printed using Objet24 3D-Printer (Stratasys) which uses a UV-curing material VeroWhite (Stratasys). 3D skin constructs were generated in six-well-plate transwell inserts similar to the method described previously^{39 (link)}. The dermal compartment was prepared by adding 4 mL of type I collagen matrix containing 1.25 × 10⁵ fibroblasts per ml into the transwell inserts and polymerized around the 3D-printed HF molds placed on top of the gel at 37 °C for 30 mins. After complete polymerization, the molds were removed and 100 μl of DPC cell suspension at a density to give 3000 DPCs per microwell was added on top of the gel (e.g. 7 million cells per ml for 255 HF per cm²). The constructs were cultured overnight in DMEM with 10% FBS for aggregate formation, after which 1 million KCs were added on top of the gel. The constructs were maintained in low calcium epidermilization medium^{39 (link)} submerged for 1–3 weeks.

To validate the depth estimation and to show its possibilities and limitations, an eye model (scale 1:1) incorporating an interchangeable fundus was designed and realized (Fig. 1). The scale was chosen to realistically mimic the geometry of the human eye, especially the anterior parts starting with the cornea. This is a crucial factor in terms of strong reflections and disturbing stray light by the interaction of illumination and imaging light. To avoid low-contrast images due to overlaying reflections and stray light in the imaging path, the separation of illumination and imaging at these parts of the eye is necessary.
The fundus had a radius of 10 mm and papilla excavations of 0.2, 0.4, 0.8, and 1.0 mm, respectively (Fig. 2). The eye model’s total length was 24.25 mm. The cornea was a custom, uncoated N-BK7 lens (outer radius 7.707 mm, inner radius 8.886 mm, and thickness 1.5 mm). The lens was an uncoated achromat (AC127-19, Thorlabs GmbH, Munich, Germany). The lens mount, housing, and fundus were printed with a 3D printer (Objet30 Prime, Stratasys Ltd., Eden Prairie, USA) with a resolution of $25\mu \mathrm{m}$ . The material used was white plastic (VeroWhite™, Stratasys Ltd., Eden Prairie, USA). The fundus models were also painted with red acrylic lacquer (Molotow™, Feuerstein GmbH, Lahr, Germany), and vessels were drawn with a thin brush by a professional artist.