Umbrella valves are designed to open and close based on the pressure of fluid (either liquidor gas) within a system. They work on a simple principle: when the pressure on the input side exceeds the pressure on the outlet side, the valve opens, and when the pressure on theoutlet side exceeds the input side, the valve closes.

Designing an umbrella valve involves several factors:

1. Material Choice: The material of the valve must be compatible with the fluid that it will handle. For example, silicone is often chosen due to its flexibility, heat resistance, and biocompatibility, which is essential for medical applications. However, other materials maybe used depending on the application.

2. Dimensions: The dimensions of the valve, including the size of the opening and the thickness of the umbrella, should be appropriate for the flow rate and pressure. The valve size will also be determined by the space constraints of the device or system in which it is being used.

3. Sealing Mechanism: The sealing surface or "seat" of the umbrella valve is crucial. It must form a perfect seal when closed to prevent any backflow. It should also open easily when pressure is applied to ensure proper fluid flow.

4. Opening Pressure: This refers to the pressure required to open the valve. lt will depend on the thickness and flexibility of the umbrella material, the size of the valve, and the application's needs.

5. Flow Rate: The design must accommodate the required flow rate of the system in which it will be used

6. Operating Conditions: The design of the valve must take into account the operating conditions, including temperature, pressure, and potential exposure to chemicals or other corrosive substances.

7. Lifecycle Requirements: The expected lifespan of the valve and the maintenance or replacement schedule should be considered. Silicone valves are often chosen for theirdurability and longevity.

To create an umbrella valve, a detailed design is usually created first, often with the help of computer-aided design (CAD) software. The design is then prototyped using appropriate materials. The prototype valve can be tested under different conditions to ensure it meets all the required specifications before mass production.

Given the technical nature of valve design, it is often carried out by engineers or technical professionals with experience in fluid dynamics and material properties. It is important to ensure that all considerations have been accounted for and that the final product meets all safety and performance standards.