Hypodermic needle having an impedance sensor for sensing penetration depth

摘要

An apparatus 100 having a shaft 102 that can sense the depth of penetration, for penetrating into an object (the substrate). The substrate being penetrated has impedance that varies according to the depth under a surface of the substrate. The shaft 102 has a tip 114 for penetration and has conductive ends 123, 125 near to the tip 114 of the shaft 102. A change of impedance of material of the object between the conductive ends 123, 125 can be sensed to provide information on the depth of penetration. A processor 108 can be provided external to the object being penetrated by the shaft 102 to gather and process the impedance information to determine whether the desired depth has been achieved.