The present invention relates to a micromechanical sensor for analyzing liquid samples and an array of such sensors. The invention also concerns a method for sensing liquid samples and the use of longitudinal bulk acoustic waves for analyzing liquid phase samples micromechanically. The sensor comprises a body and a planar wave guide portion spaced from the body. At least one electro-mechanical transducer element are used for excitation of longitudinal bulk acoustic waves to the wave guide portion in response to electrical actuation and for converting acoustic waves into electrical signals. The wave guide portion is provided with a sample-receiving zone onto which the sample can be introduced. By means of the invention, the sensitivity of micromechanical liquid sensors can be improved.