A module array includes a lead-in transmission line from a driving source. A volume-increasing phase change of the particles is suppressed by the pressure exerted on them by the metallic matrix. The indentations of the Z-trigger are located on an outer side and an inner side of the shotgun to cause substantially lateral bending when sufficient force is applied to the shotgun. The lower locking nut has a threaded hole and an engaging ring engaging the locking ring. The method improves the efficiency and success rate of multimedia message delivery and lowers the cost of multimedia message delivery. The stress sensor permits measurement of stress, preferably a shear component of the stress substantially exclusive of the normal component.