Design of microgrippers based on amorphous-crystalline TiNiCu alloy with two-way shape memory

Abstract

Functional layered composites of the shape memory alloys are recently recognized as promising basic active element for microsystem technology and microrobotics. Amorphous-crystalline TiNiCu alloy ribbons at around 40 μm of thickness with an interface separating the amorphous and crystalline phases into layers were produced by melt spinning technique. It is shown that a decrease in the cooling rate of the melt from 8.9·105 to 4.2·105 K/s leads to an increase in the thickness of the crystalline layer from 2 to 10 μm. The ratio of the thicknesses of the amorphous dam and crystalline dcr layers was also varied by an electrochemical polishing method. The composite ribbons have exhibited the two-way shape memory effect (TWSME) of thermal induced bending deformation without additional thermomechanical training. It was established that when the ratio dcr/dam is changed from 0.06 to 0.35, the minimum bending radius of the ribbon decreases from 37.1 to 6.3 mm, and the maximum reversible strain increases by 0.05% to 0.27%. The minimum time of the shape recovery of the composite ribbons when heated by an electric current pulse was 14 ms, and the force generated by the ribbon with a length of 3 mm in bending reached 1.2 mN. A series of the microgrippers (microtweezers) were fabricated on the basis of the composite ribbons with TWSME. Complete technological process of manipulating graphite filaments with a diameter of 5 to 25 μm using developed microgrippers was demonstrated.