Electronfieldemission from an array of patterned pyramids of polycrystalline diamond has been investigated for microsensor applications. Selective deposition and molding of a polycrystalline diamondfilm in a silicon cavity mold and subsequent creation of a freestanding polycrystalline diamond diaphragm with diamond pyramidal microtips has been achieved. The processing techniques are compatible with IC and micromachining technologies. High current emission from the patterned diamond microtip arrays is obtained at low electric fields. Field emission for these diamond microtips exhibits significant enhancement in total emission current compared to silicon emitters. Moreover, field emission from patterned polycrystalline diamond pyramidal-tip arrays is unique in that the applied field is found to belower than the required for emission from S1, Ge, GaAs, and metal surfaces. The findings suggest the potential use of diamond-based field-emitter arrays in microsensors such as pressure sensors, accelerometers, and tactile sensors.