What are the requirements for silicone as a 3D printing material?

What are the requirements for silicone as a 3D printing material?
In terms of material performance
Flowability: For liquid silicone, it needs to have appropriate flowability during the printing process. If it is too thin, the material may flow during printing and cannot be accurately formed. If it is too thick, it is difficult to extrude from the print nozzle, affecting the smooth progress of printing. For example, silicone resin used for photocuring 3D printing needs to maintain good photocuring performance at low viscosity so that it can be quickly cured and formed under the action of light.
Curing characteristics: Silicone usually needs to be cured by light, heat or chemical methods. As a 3D printing material, it requires a moderate curing speed. Too slow curing will make the printing efficiency low, and when printing multi-layer structures, the uncured material may deform or collapse; too fast curing may cause the nozzle to be blocked during printing, or the bonding between layers may not be strong. For example, silicone cured by ultraviolet light needs to have good sensitivity to ultraviolet light and can be cured in a short time.
Flexibility and strength: According to the different application scenarios of printed products, silicone needs to have corresponding appropriate flexibility and strength. For example, silicone used to make soft robot grippers must be highly flexible and able to withstand a certain gripping force to ensure that it will not be easily torn or damaged during use; when used in some structures that require support, silicone needs to have a certain hardness and compressive strength.
Thermal stability: Silicone should have good thermal stability and be able to maintain stable performance within a certain temperature range. If a high temperature environment is involved during the printing process, or the printed product will be used under high temperature conditions, silicone with poor thermal stability may deform, discolor, and perform poorly. For example, 3D printed silicone parts used in electronic devices need to be able to withstand the heat generated by the operation of electronic products.
Biocompatibility: If silicone is used in the medical field, such as making prostheses, medical models or implants, it must have good biocompatibility, be non-toxic, non-irritating, non-immunogenic, etc., and will not have adverse effects on human tissues. For example, silicone used to print prosthetic pads must be in long-term contact with human skin, and biocompatibility is a crucial indicator.