An implantable artificial sphincter system provides long-term adjustment via transcutaneous energy transfer (TET), minimizing invasive adjustment through adding or removing fluid via a syringe. An infuser device provides bi-directional fluid transfer via a flexible conduit to a sphincter band, such as a gastric band, by a combination of thermodynamic actuation and a piezo-electrically disengaged drum brake assembly that thereby achieves a desirable small volume device. A propellant within a propellant cavity surrounds a metal bellows accumulator biased at body temperature to either expand or collapse the bellows accumulator with the opposite direction of movement effected by a thermal element that heats in combination with a negatively-biased propellant or cools in combination with a positively-biased propellant. A drum brake assembly locks the metal bellows accumulator in place between adjustments by thermodynamic actuation by activating piezo-electric stack actuators that disengage calipers from a brake drum attached to the bellows accumulator.