P. V. Lega

Actuators based on composite material with shape-memory effect

A new scheme of composite functional material based on an alloy exhibiting a shape-memory effect (SME) is proposed. The scheme provides for a giant reversible bending deformation with the use of only “one-way”-SME alloy. An experiment was performed with the use of actuator models manufactured by gluing together the rapidly quenched ribbons and electroplating the pseudoplastically predeformed ribbons of the alloy with nickel. It is shown that the theoretical estimates of the bending moment developed by the actuator and of the reversible deformations of the actuator are in good agreement with the results of the model experiments. The prospects for the use of the new scheme in micro- and nanomechanics are considered. Actuators with record small overall dimensions have been manufactured by the focused ion-beam technique.

Shape memory effect in nanosized Ti2NiCu alloy-based composites

The shape memory effect (SME) in alloys with a thermoelastic martensite transition opens unique opportunities for the creation of miniature mechanical devices. The SME has been studied in layered composite microstructures consisting of a Ti2NiCu alloy and platinum. It occurs upon a decrease in the active layer thickness at least to 80 nm. Some physical and technological restrictions on the minimum size of a material with SME are discussed.

The smallest and the fastest shape memory alloy actuator for micro- and nanorobotics

Samples of thermally controlled shape memory alloy (SMA) composite nanotweezers based on bilayered structures Ti2NiCu/Pt with dimensions (0.8–30)×(0.1–10)×(0.07–2)μm have been developed. Each of these composites could be used to create the smallest miniature devices to date for micro- and nanomechanics, fluidics, electronics, medicine and S&A technologies. It was found that the reversible deformation of the composite created by FIB milling is greater than 1 % when the thickness of SMA layer varies from 1μm to 100 nm. The new system of nanotweezers actuation by application of electric current is proposed and theoretical modeling of the new system was done. Experimental tests of the new control system of nanotweezers have been performed. The actuation of nanotweezers in a full cycle (open — close — open) was demonstrated with frequency as high as 1 kHz. Further increase of frequency causes the decrease of bending deformation of nanotweezers. Nevertheless, even at 100 kHz self-oscillation have been detected directly under constant voltage apply. We have demonstrated 3D manipulation of 30 nm single carbon nanotube, stack of graphene layers, viskers of different materials and even mosquitos hair.

Simulation of Control System for Shape Memory Nanotweezers

Thermoelastic martensitic phase transition in Ni-Ti based shape memory alloys enables designing micro- and nanotools that are controlled by small changes in temperature (~10°С). This makes it feasible creating a new generation of complex microrobotical systems for manipulation and treatment of various nanoobjects in nanoindustry, medicine, nanoelectronics, etc. This work deals with the development of a physical and mathematical model for the micro manipulation system. The system under investigation pertains to shape memory composite nanotweezers with the composition Ti2NiCu/Pt located at the tip of a tungsten microneedle. The activation and control of the nanotweezers is done by heating them by the passage of an electric current flowing through a microdiode located in the needle. The microdiode serves the twin purpose of Joule heating and temperature sensing/measurement so as to close the feedback loop of the control system. The prototype of the control system was manufactured and tested. The data from the simulation were compared with those from the preliminary experiments.

Delay Effect for Pulsed Excitation of Actuator Based on Rapidly Quenched Ti 2 NiCu Alloy with Thermoelastic Martensitic Transformation

The pulse response of the actuator based on rapidly quenched Ti2NiCu alloy with a thermoelastic martensitic transformation and the shape memory effect is studied experimentally. The mechanical response of the actuator cooled by running water is preserved when the duration of the excitation (activating) electric pulses decreases to 2 ms. High-speed activation is accompanied by a delay in the mechanical pulse in comparison with the excitation electric pulse. The minimum duration of the mechanical pulse, taking into account the delay, was 8 ms, which corresponds to a frequency of 125 Hz with periodic activation. Estimates show that the delay time includes both the time of mechanical inertia and the time of thermal inertia associated with heat transfer. The possible limitation of the rate of activation due to kinetic phenomena during the thermoelastic martensitic transition is evaluated.

High-Speed Composite Microactuator Based on Ti 2 NiCu Alloy with Shape Memory Effect

Samples of microactuators are made of a bimorph composite of Ti2NiCu alloy with a thermoelastic martensitic transition and the shape memory effect, and their response rate is investigated. The active layer of the composite actuator is a layer of the rapidly quenched Ti2NiCu alloy, pseudoplastically prestretched, and an amorphous layer of the same alloy is used as an elastic layer. Typical sizes of the microactuator are 30 × 2 × 2 μm. The controlled amplitude of the displacement of the microactuator tip is approximately 1 μm. The response rate of the microactuator was investigated by scanning electron microscopy. Activation of the microactuator was achieved by heating when electric pulses were passed through it. Full activation of the microactuator at frequencies up to 1 kHz was demonstrated; partial activation was observed at frequencies up to 8 kHz. The possibility of operating the device in a self-oscillating mode at frequencies of the order of 100 kHz is demonstrated.

Structure and Morphology of Zinc Oxide Nanorods

The properties of nanorods made of high-energy-gap ZnxMg1 – xO semiconductors are experimentally investigated using the new system of 3D manipulation of individual nanospecimens. The technology used to prepare ZnxMg1 – xO nanorods via gas-phase deposition on a substrate, the process whereby individual nanorods are selected by means of nanocomposite tweezers with the shape-memory effect in the vacuum chamber of a two-beam scanning microscope, and the results obtained when their structure and morphology are experimentally studied using transmission electron spectroscopy are described. The prospects that nanophotonic, nanosensorial, and nanoelectronic devices can be fabricated from ZnxMg1 – xO nanorods via the new nanomanipulation technique are discussed.

Fundamental Limitations on Miniaturization of Shape-Memory Micromechanical Devices. Thermoelastic Martensite Transformation on Micro-, Nano-, and Mesoscales

TEM measurements are used to experimentally study thermoelastic martensite transformation in Ti2NiCu tapered plates. The martensite phase is observed at room temperature in the Ti2NiCu alloy when the plate thickness decreases to, at least, 80 nm, and the austenite phase is observed at smaller thicknesses. It is shown that the temperature of thermoelastic martensite transition in the Ti2NiCu alloy decreases with a decrease in the thickness of the plate, the transition is blocked at a thickness of less than 20 nm, and a hysteresis dependence is observed. Possible physical and technological reasons for blocking of the martensite phase transition on nanoscale and fundamental limitations on the sizes of micromechanical devices based on the shape-memory Ti2NiCu alloy are considered.

Self-Detection of High-Frequency Mechanical Oscillations of Whiskers in Quasi-1D Conductors with Charge-Density Wave

Heterodyne mixing with frequency modulation is employed for detection of torsional resonances of whiskers in rhombic TaS3 (typical quasi-1D conductor) with charge-density wave (CDW). The dependences of both torque and the feedback signal of torsion on the internal properties of CDW are distinctive features of the proposed method. Sample placement in the vicinity of the electrode that serves as gate is unnecessary. Electromechanical and elastic properties of the CDW systems can be studied with the aid of the proposed method, at least, in the megahertz frequency range.

Structure and thermomechanical properties of fast-quenched Ti2NiCu alloy ribbons with various crystalline phase fractions obtained by means of annealing by electric current

New promising functional materials—amorphous-crystalline fast-quenched Ti2NiCu alloys exhibiting the shape memory effect (SME)—are studied. A method for annealing amorphous alloys by electric current pulses is proposed. This method allows one to obtain the needed degree of crystallinity. It is demonstrated that a microcrystalline structure with spherical grains exists in amorphous-crystalline samples. These grains increase in size from 150 nm to 3.2 μm as the degree of annealing increases. The SME is not observed in nontreated samples and is clearly manifested in completely annealed samples. A two-way SME and a trend toward lowering of the martensitic transition temperature are observed in partially annealed samples.