Most mechanical tests (compression testing, tensile testing, flexure testing, shear testing) of samples in the sub-mm size scale are performed under the observation with an optical microscope or a scanning electron microscope. However, the following problems exist with prior art force sensors as e.g they cannot be used for in-plane mechanical testing (a- and b-direction) of a sample; they cannot be used for vertical testing (c-direction) of a sample. In order to overcome the before mentioned drawbacks the invention comprises the following basic working principle: A force is applied to the probe (2) at the probe tip (1) of the sensor. The force is transmitted by the sensor probe (2) to the movable body (3) of the sensor. The movable body is elastically suspended by four folded flexures (4), which transduce the force into a deflection dx. This deflection is measured by an array of capacitor electrodes, called capacitive comb drive (6).