What is the fine-grained topic of the following text: These devices are typically sterile and flexible single-use sponges made from a variety of materials including cotton, rayon, and polyester; the outer components of the sponge are usually made of a porous plastic material which prevents the sponge from adhering to the tissue and avoids tearing the tissue when removed. Only return the topic.
Materials and design of single-use medical sponges