Guide wire devices fabricated from a linear pseudo-elastic NiTi alloy and methods for their manufacture. The NiTi alloy that includes nickel, titanium, and about 3 atomic % (at %) to about 30 at % niobium (Nb). Cold working the NiTi alloy stabilizes the alloy's martensitic phase and yields a linear pseudo-elastic microstructure where reversion to the austenite phase is retarded or altogether blocked. The martensitic phase of cold worked, linear pseudo-elastic NiTiNb alloy has an elastic modulus that is considerably higher than the comparable cold worked, linear pseudoelastic binary NiTi alloy. This yields a guide wire device that has better torque response and steerability as compared to cold worked, linear pseudoelastic binary NiTi alloy or superelastic binary NiTi alloy.

A method for manufacturing a functional elongate instrument includes: a base material preparation step of obtaining a wire-inserted base material by inserting a first wire as an actuator member through a first through-hole of a plurality of through-holes formed in a base material and inserting a second wire opposite to the first wire through a second through-hole of the plurality of through-holes; a composite fiber formation step of obtaining a composite fiber by heating and drawing the wire-inserted base material while supplying the first wire and the second wire; a connection step of forming, at a tip portion of the composite fiber, a connection portion configured to electrically connect the first wire and the second wire; and an insulation step of forming an insulating layer on a surface of the connection portion.