The surface of the Xiaomi Instant Hot Water Dispenser can develop a mucous residue over time due to the formation of a microscopic water film when the silicone tube is exposed to water for extended periods. This film can give the silicone surface a greasy feel. Rest assured that the materials used in the water dispenser meet stringent food safety standards, ensuring it is safe for continued use. To maintain cleanliness, you can easily wipe the surface with clean water, which will help remove any residue and keep the water dispenser in good condition.