scholarly journals Temperature Homogenization of Co-Integrated Shape Memory—Silicon Bimorph Actuators

Proceedings ◽  
2020 ◽  
Vol 64 (1) ◽  
pp. 8
Author(s):  
Gowtham Arivanandhan ◽  
Zixiong Li ◽  
Sabrina Curtis ◽  
Prasanth Velvaluri ◽  
Eckhard Quandt ◽  
...  
Keyword(s):  
Shape Memory ◽  
Joule Heating ◽  
Temperature Gradients ◽  
Fem Simulations ◽  
Electrothermal Actuation ◽  
Double Beam ◽  
Temperature Homogenization ◽  
Bimorph Actuators ◽  
Increasing Temperature ◽  
High Work

The high work density and beneficial downscaling of shape memory alloy (SMA) actuation performance provide a basis for the development of actuators and systems at microscales. Here, we report a novel monolithic fabrication approach for the co-integration of SMA and Si microstructures to enable SMA-Si bimorph microactuation. Double-beam cantilevers are chosen for the actuator layout to enable electrothermal actuation by Joule heating. The SMA materials under investigation are NiMnGa and NiTi(Hf) films with tunable phase transformation temperatures. We show that Joule heating of the cantilevers generates increasing temperature gradients for decreasing cantilever size, which hampers actuation performance. In order to cope with this problem, a new method for design optimization is presented based on finite element modeling (FEM) simulations. We demonstrate that temperature homogenization can be achieved by the design of additional folded beams in the perpendicular direction to the active beam cantilevers. Thereby, power consumption can be reduced by more than 35 % and maximum deflection can be increased up to a factor of 2 depending on the cantilever geometry.

scholarly journals Optimization of MEMS Actuator Driven by Shape Memory Alloy Thin Film Phase Change

2020 ◽  
Author(s):  
Cory R. Knick
Keyword(s):  
Shape Memory Alloy ◽  
Phase Change ◽  
Shape Memory ◽  
Curvature Radius ◽  
Alloy Thin Film ◽  
Individual Layer ◽  
Cantilever Length ◽  
Stress Changes ◽  
Bimorph Actuators ◽  
High Work

At the microscale, shape memory alloy (SMA) microelectromechanical system (MEMS) bimorph actuators offer great potential based on their inherently high work density. An optimization problem relating to the deflection and curvature based on shape memory MEMS bimorph was identified, formulated, and solved. Thicknesses of the SU-8 photoresist and nickel-titanium alloy (NiTi) was identified that yielded maximum deflections and curvature radius based on a relationship among individual layer thicknesses, elastic modulus, and cantilever length. This model should serve as a guideline for optimal NiTi and SU-8 thicknesses to drive large deflections and curvature radius that are most suitable for microrobotic actuation, micromirrors, micropumps, and microgrippers. This model would also be extensible to other phase-change-driven actuators where nonlinear and significant residual stress changes are used to drive actuation.

scholarly journals Origami-Inspired Shape Memory Folding Microactuator

Proceedings ◽  
2020 ◽  
Vol 64 (1) ◽  
pp. 6
Author(s):  
Lena Seigner ◽  
Olha Bezsmertna ◽  
Sebastian Fähler ◽  
Georgino Kaleng Tshikwand ◽  
Frank Wendler ◽  
...  
Keyword(s):  
Shape Memory ◽  
Joule Heating ◽  
Electrical Current ◽  
Planar System ◽  
Beam Structures ◽  
Setting Process ◽  
Double Beam ◽  
And Performance ◽  
The One ◽  
Maximum Heating

This paper presents the design, fabrication and performance of origami-based folding microactuators based on NiTi films showing the one-way shape memory effect. Freestanding NiTi films are micromachined by laser cutting or photolithography to achieve double-beam structures allowing for direct Joule heating with an electrical current. The NiTi microactuators are interconnected to rigid sections (tiles) forming an initial planar system that self-folds into a predetermined 3D shape upon heating. A thermo-mechanical treatment is used for shape setting of as-received specimens to approach a maximum folding angle of 180°. The bending moments, bending radii and load-dependent folding angles upon Joule heating are evaluated. The shape setting process is particularly effective for small bending radii, which, however, generates residual plastic strain. After shape setting, unloaded beam structures show recoverable bending deflection between 0° and 140° for a maximum heating power of 900 mW. By introducing additional loads to account for the effect of the tiles, the smooth folding characteristic evolves into a sharp transition, whereby full deflection up to 180° is reached.

scholarly journals Induction of Changes in Internal Gas Pressure of Bulky Plant Organs by Temperature Gradients

1990 ◽  
Vol 115 (2) ◽  
pp. 308-312 ◽  
Author(s):  
Kenneth A. Corey ◽  
Zhi-Yi Tan
Keyword(s):  
Bath Temperature ◽  
Ideal Gas ◽  
Gas Pressure ◽  
Temperature Gradients ◽  
Maximum Pressure ◽  
Plant Organs ◽  
Ideal Gas Law ◽  
Increasing Temperature ◽  
Pressure Changes

Water manometers were connected to fruits of tomato (Lycopersicon esculentum Mill.) and pepper (Capsicum annuum L.), and then fruits were submerged in water baths providing initial temperature gradients between fruit and water of 0 to 19C. Apple (Malus domestics Borkh.) fruits, carrot (Daucus carota L.) roots, witloof chicory (Cichorium intybus L.) roots, rhubarb Rheum rhabarbarum L.) petioles, and pokeweed (Phytolacca americana L.) stems were subjected to water bath temperature gradients of 5C. Internal partial vacuums developed in all organs within minutes of imposing the gradients. The maximum partial vacuums in tomato and pepper fruits increased with increasing temperature gradients. Uptake of water accompanied changes in internal pressure reaching maxima of 17% (w/w) and 2% (w/w) of pepper and tomato fruits, respectively, after 22 hours. Maximum pressure changes achieved in bulky organs deviated from those predicted by the ideal gas law, possibly due to concomitant changes in gas pressure upon replacement of intercellular spaces with water and dissolution of CO2. Partial vacuums also developed in pepper fruits, rhubarb petioles, and pokeweed stems following exposure to air 15C cooler than initial organ temperatures. Results point to the role of temperature gradients in the transport of liquids and gases in plant organs.

Dynamic observation of Joule heating-induced structural and domain transformation in smart shape-memory alloy

2020 ◽  
Vol 186 ◽  
pp. 223-228 ◽  
Author(s):  
Abdul Karim ◽  
Chaoshuai Guan ◽  
Bin Chen ◽  
Yong Li ◽  
Junwei Zhang ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Joule Heating ◽  
Dynamic Observation ◽  
Domain Transformation

Microstructural Evolution during Sintering of the P/M Blended Elemental Ti-5Al-2.5Fe Alloy

2005 ◽  
Vol 498-499 ◽  
pp. 55-60 ◽  
Author(s):  
Rodrigo P. Siqueira ◽  
Hugo Ricardo Zschommler Sandim ◽  
Vinicius André Rodrigues Henriques ◽  
J.F.C. Lins
Keyword(s):  
Microstructural Evolution ◽  
Cost Effective ◽  
X Ray Diffraction ◽  
Blended Elemental ◽  
Surgical Implants ◽  
Diffusion Controlled ◽  
Effective Option ◽  
Temperature Homogenization ◽  
Increasing Temperature ◽  
Cold Pressed

The alpha-beta Ti-5%Al-2.5Fe (wt-%) alloy was developed as a cost-effective option to replace the traditional Ti-6%Al-4%V alloy in the manufacture of surgical implants because of its larger biocompatibility (V-free alloy). Samples of this alloy were prepared using the blended elemental (BE) technique. The isochronal sintering of the cold pressed compacts was carried out at 700, 1000, and 1400°C in vacuum. In this work, the preliminary results of the behavior of elementary powders during sintering and the corresponding microstructural evolution are shown. The alloy was characterized by means of scanning electron microscopy (SEM) in the backscattered mode, X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), and density measurements. The results indicate that the homogenization of the alloy is diffusion-controlled. Non-equilibrium Ti-Al phases as well as Fe-Al compounds were identified in samples sintered at lower temperatures (700oC). With increasing temperature, homogenization of the alloy takes place and a structure consisting of coarse plate-like alpha and intergranular beta is present.

Stability of ni-ti shape memory alloy wire during thermo-mechanical cycling using the joule heating effect

2015 ◽  
Author(s):  
Walber Medeiros Lima ◽  
Jackson de Brito Simões ◽  
Rodinei Medeiros Gomes ◽  
Cícero da Rocha Souto ◽  
Tadeu Antônio de Azevedo Melo ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Joule Heating ◽  
Shape Memory Alloy Wire ◽  
Heating Effect ◽  
Alloy Wire ◽  
Joule Heating Effect ◽  
Mechanical Cycling

Influence of carbon black properties on the Joule heating stimulated shape-memory behavior of filledethylene-1-octene copolymer

2010 ◽  
Vol 51 (3) ◽  
pp. 500-508 ◽  
Author(s):  
Hai Hong Le ◽  
Osayuki Osazuwa ◽  
Igor Kolesov ◽  
Sybill Ilisch ◽  
Hans-Joachim Radusch
Keyword(s):  
Carbon Black ◽  
Shape Memory ◽  
Joule Heating ◽  
Shape Memory Behavior

An Analytical Design Method for a Shape Memory Alloy Wire Actuated Compliant Finger

2008 ◽  
Author(s):  
Chao-Chieh Lan ◽  
You-Nien Yang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Design Method ◽  
Three Dimensional ◽  
Output Force ◽  
Shape Parameterization ◽  
Robotic Manipulations ◽  
Experimental Validations ◽  
Electro Magnetic ◽  
High Work

This paper presents an analytical method to design a mechanical finger for robotic manipulations. As traditional mechanical fingers require bulky electro-magnetic motors and numerous relative-moving parts to achieve dexterous motion, we propose a class of fingers the manipulation of which relies on finger deflections. These compliant fingers are actuated by shape memory alloy (SMA) wires that exhibit high work-density, frictionless, and quite operations. The combination of compliant members with embedded SMA wires makes the finger more compact and lightweight. Various SMA wire layouts are investigated to improve their response time while maintaining sufficient output force. The mathematical models of finger deflection caused by SMA contraction are then derived along with experimental validations. As finger shapes are essential to the range of deflected motion and output force, we find its optimal initial shapes through the use of a shape parameterization technique. We further illustrate our method by designing a humanoid finger that is capable of three-dimensional manipulation. As compliant fingers can be fabricated monolithically, we expect the proposed method to be utilized for applications of various scales.

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