A sensor assembly is provided that includes a frame having a loop structure. An emitter and detector are disposed on opposite sides of the loop structure. A coating is provided over the frame. The coating includes at least one diaphragm structure disposed such that at least one of the emitter and detector can move along an axis running between the emitter and detector. The sensor may thereby be placed on a patient's finger, toe, and so forth to obtain pulse oximetry or other physiological measurements. A sensor frame and method of manufacturing the frame are also provided.