Vacuum-deposited TiNi shape memory film: characterization and applications in microdevices

Johnson, A. David

doi:10.1088/0960-1317/1/1/007

Cited by 112 publications

(35 citation statements)

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“…Ni-Ti-based thin films are gaining technological interest as microelectro-mechanical system-based microactuators because their work output per volume exceeds that of other microactuation mechanisms. [1][2][3][4] Other advantages of Ni-Ti-based thin film includes high-power density, large displacement, and an actuation force resulting from the high surface-area-tovolume ratio with an enhanced cooling rate leading to a faster response speed in the micron size actuators. [4,5] Because of the difference in the coefficient of thermal expansion between the substrate and the SMA thin film, Ni-Ti-based films can act as bimorphs that are sensitive to the working temperature.…”

Section: Introductionmentioning

confidence: 99%

“…The magnetron sputtering technique is the most popular PVD process used to fabricate NiTi films of higher deposition rates with precise composition control desired for a choice of application. [2,3] In addition to controlling the working temperature, composition adjustment becomes a prime requisite for the fabrication of Ni-Ti thin film microactuator. [4] The shape memory characteristics and transformation behavior of Ni-Ti microactuators are sensitive to metallurgical factors and sputtering variables.…”

Section: Introductionmentioning

confidence: 99%

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An Investigation on Phase Formations and Microstructures of Ni-rich Ni-Ti Shape Memory Alloy Thin Films

Priyadarshini

Aich²,

Chakraborty³

2010

Metall Mater Trans A

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Ni-rich Ni-Ti alloy thin films were fabricated by radio frequency (RF)-direct-current (DC) magnetron sputtering using elemental Ni and Ti as sputter targets. Si (100) was chosen as a substrate that was either held at room temperature or at 573 K (300°C) during the depositions. The 380-nm-thick films were characterized by field emission scanning electron microscopy, energy dispersive spectroscopy, grazing incidence X-ray diffraction, atomic force microscopy, high-resolution transmission electron microscopy, and Vickers microhardness tester. The results suggests that because of the lack of surface mobility of the adatoms at the room temperature, the deposited films were smooth and amorphous, with a crystallite size of 15 nm accompanied with a porous morphology. At higher substrate temperatures, an increase in the surface diffusion leads to the formation of partially crystalline, rougher films with a denser, compact, fibrous grain microstructure. The formation of Ni-rich precipitates such as Ni 4 Ti 3 , Ni 2 Ti, and Ni 3 Ti along with small amount of the NiTi phase were attributed to the localized heating and cooling within the grains. Few grains exhibited band structures that are believed to be a result of<110> type II twins.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Investigation on Phase Formations and Microstructures of Ni-rich Ni-Ti Shape Memory Alloy Thin Films

Priyadarshini

Aich²,

Chakraborty³

2010

Metall Mater Trans A

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“…Another means of actuation that makes use of phase transformations is the shape memory effect, which is exhibited by shape memory alloys (SMA) such as TiNi [122], [123]. This thermally induced crystalline transformation between a ductile (Martensitic) phase and a high strength (Austenitic) phase has been harnessed in MEMS with the use of thin film deposition techniques such as dual target sputtering.…”

Section: Micro-scale Actuatorsmentioning

confidence: 99%

Single‐Chip Scanning Probe Microscopes

Sarkar

Mansour²

2015

Micro‐ and Nanomanipulation Tools

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Scanning probe microscopes (SPMs) are the highest resolution imaging instruments available today and are among the most important tools in nanoscience. Conventional SPMs suffer from several drawbacks owing to their large and bulky construction and to the use of piezoelectric materials. Large scanners have low resonant frequencies that limit their achievable imaging bandwidth and render them susceptible to disturbance from ambient vibrations. Array approaches have been used to alleviate the bandwidth bottleneck; however as arrays are scaled upwards, the scanning speed must decline to accommodate larger payloads. In addition, the long mechanical path from the tip to the sample contributes thermal drift. Furthermore, intrinsic properties of piezoelectric materials result in creep and hysteresis, which contribute to image distortion. The tip-sample interaction signals are often measured with optical configurations that require large free-space paths, are cumbersome to align, and add to the high cost of state-of-the-art SPM systems. These shortcomings have stifled the widespread adoption of SPMs by the nanometrology community. Tiny, inexpensive, fast, stable and independent SPMs that do not incur bandwidth penalties upon array scaling would therefore be most welcome. A method to increase the quality factor (Q-factor) of flexural resonators is introduced. The method relies on an internal energy pumping mechanism that is based on the interplay between electrical, iv mechanical, and thermal effects. To the best of the author's knowledge, the devices that are designed to harness these effects possess the highest electromechanical Qs reported for flexural resonators operating in air; electrically measured Q is enhanced from ~50 to ~50,000 in one exemplary device. A physical explanation for the underlying mechanism is proposed.The design, fabrication, imaging, and tip-based lithographic patterning with the first single-chip Scanning Thermal Microscopes (SThMs) are also presented. In addition to 3 DOF scanning, these devices possess integrated, thermally isolated temperature sensors to detect heat transfer in the tip-sample region.Imaging is reported with thermocouple-based devices and patterning is reported with resistive heater/sensors. An "isothermal electrothermal scanner" is designed and fabricated, and a method to operate it is detailed. The mechanism, based on electrothermal actuation, maintains a constant temperature in a central location while positioning a payload over a range of >35μm, thereby suppressing the deleterious thermal crosstalk effects that have thus far plagued thermally actuated devices with integrated sensors.

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“…The actuator size, and thus the consumed valve footprint area for these devices, must be large in comparison to the minimum flow cross-sectional area, which prohibits large component counts per batch. Microvalves with actuation principles that require manual assembly include electrostatic actuation [8], [9], electromagnetic actuation [10], shape-memory alloy actuation [11], thermopneumatic actuation [12], and piezoelectric actuation [13], [14]. These valves offer larger energy density and larger stroke than do other techniques, however, cost more to assemble.…”

Section: Introductionmentioning

confidence: 99%