An enhanced composite scheme of shape memory actuator for smart systems

Abstract

An enhanced scheme of a functional composite material has been proposed and tested in the model experiments. The composite consists of an element with shape memory effect (SME) in the form of ribbon, film or plate connected rigidly to an element of an elastic material. The novel feature in this scheme is that an SME element should be preliminary given the uniaxial pseudoplastic tensile straining. This operation promotes the martensite twins formation along the stretching axis and results in the maximal longitudinal deformation of SME element. Such scheme provides a well-controlled high reversible bending deformation of the composite, though only one-way SME of the material is used. It can be applied to the most conventional shape memory materials, such as polymers, ferromagnetic and non ferromagnetic alloys. The scheme is experimentally tested on the composites made by applying an elastic layer on the preliminary pseudoplastically stretched melt-spun ribbons of the Ti50Ni25Cu25 alloy (see video on the web: www.smwsm.org/ll/composites.html). The elastic layer was applied by three different techniques: gluing, electroplating and focused ion beam assisted chemical vapor deposition (FIB/CVD). Fatigue experiments showed that the composite made by electroplating of Ni layer demonstrates fairly stable actuation for at least 2000 cycles. FIB/CVD allowed a preparing of a composite actuator with the dimensions of about 25×1×1μm. The scheme is promising for the applications in the fields of MEMS and NEMS, microfluidics and biomedical technologies.