The bottom housing is made from glycol-modified polyethylene terephthalate, and contains: anode hydrogel, including fentanyl HCl, polacrilin, purified water, sodium hydroxide, polyvinyl alcohol; cathode hydrogel, including purified water, sodium chloride, sodium citrate, polyvinyl alcohol, anhydrous citric acid, cetylpyridinium chloride; anode electrode, containing layers of silver foil and electrically conductive adhesive tape; cathode electrode consisting of layers of silver chloride composite material, silver foil, and electrically conductive adhesive tape; skin adhesive composed of a mixture of two PIBs, a polybutene, and a resin ester that acts as a tackifier; protective liner which is a polyester film coated on one side with silicone.