The Mini-Infuser^® uses a polymer actuator that we developed to replace all the mechanical components of an infusion pump. The polymer is stored dry in the Mini-Infuser^® actuator assembly. When water is introduced, the polymer actuator swells at a very linear rate and creates very high pressure. The high pressure created is transferred to the drug container which then pushes the medication out of the Mini-Infuser ^® at a very linear and controlled rate of infusion for animal and veterinary use, without the need for electric motors and mechanical parts.