Structural colors are colors that result from the interaction of light with the physical structure of a material rather than from the chemical makeup of the material. In other words, they are created by the way light waves are scattered, reflected, or diffracted by microscopic structures within the material.

Structural colors can be found in many natural phenomena, such as the iridescent colors of peacock feathers, butterfly wings, and some beetle shells. These colors can also be artificially created in man-made materials using techniques such as thin-film interference, diffraction gratings, and photonic crystals.

Unlike pigments, which absorb certain colors and reflect others, structural colors are based on the physical arrangement of materials and are not dependent on the absorption of light. This means that they can appear different depending on the viewing angle or the angle of the light source. Additionally, structural colors can be very vivid and intense, and are often used in a range of applications, from cosmetics and textiles to security features on banknotes.

When it comes to designing and manufacturing products with structural colors using injection molding, there are several critical aspects to consider:

1. Mould Design: The mould used in injection moulding plays a crucial role in the final appearance and quality of the structural colour. The mould should be designed with a precise and consistent cavity surface to ensure the uniform deposition of the colour pigment onto the moulded part. The mould should also be polished to a high degree to achieve the required surface finish.
2. Material Selection: The material used for injection molding should be chosen carefully to achieve the desired structural color effect. Certain materials, such as polycarbonate, can be used to create iridescent effects, while other materials, such as ABS, are better suited for creating a metallic or pearlescent finish.
3. Pigment Selection: The pigment used to create the structural color should be chosen based on the desired effect and the material being used. Pigment concentration, size, and distribution can all affect the final color and appearance of the molded part.
4. Processing Conditions: The injection molding process must be carefully controlled to achieve consistent and reproducible results. Factors such as temperature, pressure, and injection speed can all affect the final appearance of the structural color.
5. Part Design: The design of the molded part itself can also affect the appearance of the structural color. The surface area and curvature of the part can affect the way light interacts with the color pigments, and should be optimized to achieve the desired effect.

Overall, the design and manufacturing of products with structural colours in injection moulding requires careful attention to detail and a thorough understanding of the principles of colour and material science. By taking these critical design aspects into consideration, it is possible to create high-quality products with striking and unique structural colours.