2.2. Blink Model

The fabrication and assembly of the previous iteration of the blink model have been described in a previous study [24] (Video S1, Supplementary Materials). In brief, the eyeball was fabricated using a combination of 3D-printing and molding techniques. For this study, the front surface of the eyeball was coated with a silicone material (Alumilite High Strength 3 Silicone Rubber, Polytek Development Corp., PA, USA) to limit the absorption of the dye. The eyelid was made from a polyvinyl alcohol (PVA) material, which has been described previously [24]. The eyeballs, lower eyelid, and collection unit were printed using a hydrophobic UV-polymerizable resin on an SLA (stereolithography) printer (Photon S, Anycubic, Shenzhen, China) to ensure water-sealed parts. The collection unit was designed to allow the tear film to flow from the eyeball into the wells. The entire system, shown in Figure 1, was housed inside a chamber to maintain a stable humidity during the experiment. A schematic diagram of the collection unit is shown in Figure 2.

Design and assembly of the blink model. The downward motion of the eyelid spreads a simulated tear solution, which is supplied through the tubing that is attached to the eyelid support, over the eyeball, and a contact lens. The flow-through fluid is then collected in the collection unit located beneath the eyeball.

The collection unit allows the fluid to flow from the lower eyelid into the tray located beneath the eyeball.