1. A downhole tool for determining the properties of a fluid comprising: a downhole tool deployed in a well bore formed in an adjacent formation, the tool interacting with a downhole fluid; a resonator associated with the downhole fluid; a controller for actuating the resonator; a monitor for receiving a response from the resonator to the actuation of the resonator such that the response is associated with the fluid; and a processor for estimating a value of a property for the downhole fluid.