Pellicle

A pellicle is a thin, pliable membrane or film that covers or lines a surface. The term is used in several fields to describe different but related concepts, including a surface-adsorbed biological film, a cytoskeletal layer in some single-celled organisms, and an ultrathin optical membrane.

In dentistry, the acquired pellicle forms within minutes on exposed enamel and dentin from salivary glycoproteins and enzymes. It consists mainly of proteins and glycoproteins that adhere to the mineral surface, offering protection to the tooth surface while also serving as a substrate for bacterial adhesion and plaque formation.

In microbiology, a pellicle can refer to the visible mat or film that forms at the air–liquid interface of a liquid culture. It is composed of cells and extracellular polymeric material and can influence oxygen transfer and surface properties of the culture.

In cell biology and protozoology, the pellicle is the thin, specialized layer just beneath the plasma membrane in some unicellular eukaryotes, such as certain ciliates and euglenoids. It consists of membranes and underlying cytoskeletal elements that confer shape, rigidity, and flexibility.

In optics and photonics, a pellicle is an ultrathin, nearly transparent membrane used as a beam splitter or protective window in various instruments. Made from polymer films such as Mylar or silicon nitride, it has very low mass and can minimize optical disturbance but remains mechanically delicate.