A clutch for an electronic door lock includes a first shaft, a second shaft, a spring, a rheological fluid, and a plunger. The second shaft has an aperture therein and is axially co-aligned with the first shaft and is rotatably mounted adjacent the rotatable first shaft. The spring is disposed in the aperture in the second shaft. The rheological fluid is held within the aperture and is capable of changing viscosities in response to the application of an electrical current across the fluid. The plunger is biased by the spring into selective coupling engagement with the first shaft and is capable of selective motion into the aperture in response to contact by a camming surface of the first shaft due to relative rotation of the first shaft with respect to the second shaft.