I am also making far-infrared clothing myself, so I have also done relevant data surveys. As far as I know, there are three ways for far infrared fabrics. 1. The coating should be directly coated with a layer of far infrared on the fabric. 2. The polymer particle type should also be adhered. 3. Embedding, such as a mixture of polyamide and far-infrared bioactive mineral components, is directly formed after mixing them, usually in the form of yarn or woven fabric, without smearing. Like the first two items, repeated cleaning may be washed away and the far-infrared function may be lost, but the embedded far-infrared function of the third item will not be lost. If you are doing underwear, you can consider the third method. You can learn about the yarn called EMANA.