A slider for use in a magnetic disk drive includes read pads for connecting to a flexible circuit that couples to a pre-amplifier circuit, a transducer, and a protector connected to the transducer and the read pads to protect the transducer against damage from electrostatic discharge. The first span has a diameter suitable to guide and support light having an electromagnetic mode coupled therein without substantial optical loss. In one application, biocompatible matrixes may be formed with long pore length and small pore size. Identification data is then transmitted back to the smartphone device and displayed. The shape determined may be the shape of a pin, especially a crankpin for a crankshaft. Crucibles containing this protective coating may be used for the solidification of silicon.