Manufacturing Process for Non-Adhesive Super-Soft Vocal Fold Models

Our research aims at improving the manufacturing process of synthetic vocal folds. Such models can be used in basic phonetic and voice research, in medical research, and to create models of the human vocal tract that produce speech like human beings. Synthetic vocal fold models are usually made of multiple layers of soft silicone with different degrees of softness.

They correspond to the properties of human vocal fold tissue. The technologies used to make these models include computer edit design, 3D printing, and silicone casting. Highly diluted silicone vocal fold models have reduced quality due to stickiness and rapid aging.

This decreases the reproducibility of research using these models. This protocol addresses the issue of vocal fold stickiness. We have reversed the order of producing the silicon layers in our fabrication process.

We started with the helium layer. This allowed us to create a very soft causal layer from diluted silicone without causing the epithelium layer to become sticky, In a 3D printing program, load the STL files to generate G-code files and select the preferred 3D printer. For supplementary coating file two and supplementary coating file five, use polylactate acid or polycarbonate as printing material.

For supplementary coating file one, use a tough polylactate acid or polyethylene terephthalate glycol. Next, load supplementary coating file two and set layer height to one millimeter over profile presets. Load supplementary coating file five and set layer height to one millimeter.

Now load supplementary coating file one and set layer height to 0.2 millimeters. Set the infill value to 100%and the print pattern to zigzag. Set the build plate adhesion category to skirt.

Slice the supplementary file one. View the layered 3D model and export the G-code to a USB stick. Print the parts on the 3D printer.

After printing, clean the parts and remove excess brim or printing errors. Collect components required for manufacturing vocal fold and mold assembly. Smooth the inner contact surfaces with sandpaper.

To create a vocal body layer, collect vocal fold positive, vocalis mold cap, vocalis mold main part, vocalis mold hole, primary silicone, release agent, and thinner. Apply the release agent to the inside surfaces of all the mold parts. Assemble the main part and cap of the mold over the positive.

Then place the mold package in the designated pot. Ensure the hole in the positive for pouring the silicone faces upwards and the mold has a stable footing on a flat surface. Prepare six grams of primary silicone mixture with three parts of thinner.

To prevent bubble formation, vacuum the mixture in a vacuum chamber at a minimum of 1 bar sub pressure. Carefully pour the vacuumed silicone mixture into the mold cavity, filling the surrounding areas of the mold pot to prevent the thin silicone mixture from sinking through the mold joints. After curing for one day, remove the mold, including the positive from the pot.

Remove the silicone between the mold and the pot. Now carefully remove the lid starting from the back of the positive. Then remove the main body of the mold.

Using a scalpel or a side cutter, carefully remove the excess silicone from the mold. Assemble the two mold parts and place them in the hull. Coat the inner walls of the molds with a release agent and allow them to air dry.

Prepare a secondary silicone mixture without thinner. Vacuum the mixture in a vacuum chamber at 1 bar sub pressure to prevent bubble formation. Pour the silicone mixture into the mold and swirl it around until all interior surfaces are coated with silicone.

Secure the mold over a grate and allow the silicone to cure. Turn the mold over and let excess silicone drain out. Prepare four grams of primary silicone mixture with five parts of thinner.

To prevent bubble formation, vacuum the silicone mixture in a vacuum chamber. Pour the silicone mixture into the mucosa mold prepared with epithelial silicone. Tilt the mold to cover the interior surfaces of the epithelial silicone with a thin layer of oil.

Carefully insert the positive with the vocal body into the mold. If necessary, secure the positive with a clamp. Fill the mold with a silicone mixture for the casting of the vocalis layer.

After 24 hours of curing, remove the mold from the shell. Then starting with the rear section, open the mold and remove the main part of the mold. Remove the vocal fold model from the mold.

Carefully remove the excess silicone from the vocal body. Finally, wash the vocal body surface and allow it to dry.