A nitride semiconductor substrate having a rugged surface being lapped by whetting granules to roughness between Rms5 nm and Rms200 nm, which has a function of reducing dislocations of a GaN, InGaN or AlGaN layer epitaxially grown on the lapped substrate by gathering dislocations in the epi-layer to boundaries of holes, pulling the dislocations to bottoms of the holes. A writeread unit is disposed on the magnetic structure, and a plurality of switching devices are respectively connected to the buffer track, the plurality of storage tracks, and the writeread unit. The lead wire is received in the necklace. These items can attach by the aforementioned zippers, hook-and-loop fasteners, snaps, elastic bands, clips and the like. The flexure provides a degree of rotational flexibility to the manipulandum when the at least one actuator exerts the force.