Smart thermos cups incorporate environmentally friendly materials in the following ways:

1. **Food-grade Stainless Steel**: Smart thermos cups widely use food-grade stainless steel as the primary material. This material is not only safe and hygienic but also has excellent insulation and durability. For instance, food-grade 304 and 316 stainless steels are preferred for their corrosion resistance and high-temperature tolerance.

2. **Bio-based Plastics**: Some brands use bio-based plastics as the shell material for thermos cups. These materials are derived from renewable resources and can degrade in the natural environment, reducing environmental damage.

3. **Flexible Ceramics**: Flexible ceramic materials offer excellent insulation and durability, maintaining the temperature of beverages more effectively while reducing environmental impact.

4. **High-performance Insulation Materials**: These materials reduce heat conduction and enhance insulation efficiency while being environmentally friendly.

5. **Silicone**: Silicone is an eco-friendly, non-toxic, high-temperature resistant, and corrosion-resistant material that is also used in the production of smart thermos cups, favored for its environmental benefits.

6. **Recycled Materials**: Some companies use recycled materials in their product design to reduce carbon emissions. For example, as of 2023, the use of recycled materials by Halisi has cumulatively reduced carbon emissions by 3,666.78 tons.

7. **Eco-friendly Paper Packaging**: In product packaging, eco-friendly materials are preferred, with eco-friendly paper replacing plastic packaging to reduce plastic use and lower environmental pollution.

8. **Lead-free and Phthalate-free**: In material selection, there is a focus on the use of lead-free and phthalate-free eco-friendly materials to ensure safe and healthy drinking water.

The application of these environmentally friendly materials not only enhances the eco-friendliness of smart thermos cups but also meets consumers' pursuit of a healthy and eco-friendly lifestyle. With technological advancements and increased consumer awareness of environmental protection, it is expected that more eco-friendly materials will be applied to the production of smart thermos cups in the future.