The FlexSac mixer integrates with a mechanical actuator to provide complete, rapid powder/liquid mixing. The mixer’s single-use, disposable mixing vessel saves customers the time and expense associated with cleaning and validation. This system also has applications in general industrial mixing processes where cleanup is a concern. The system incorporates a clear tubular mixing vessel with a rigid mixing septum and fill and drain ports. The translating motion of the mixing septum creates jets that effectively serve to quickly combine ingredients.