scholarly journals Surface-Controlled Molecular Self-Alignment in Polymer Actuators for Flexible Microrobot Applications

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 736 ◽  
Author(s):  
Minsu Jang ◽  
Jun Sik Kim ◽  
Ji-Hun Kim ◽  
Do Hyun Bae ◽  
Min Jun Kim ◽  
...  

Polymer actuators are important components in lab-on-a-chip and micromechanical systems because of the inherent properties that result from their large and fast mechanical responses induced by molecular-level deformations (e.g., isomerization). They typically exhibit bending movements via asymmetric contraction or expansion with respect to changes in environmental conditions. To enhance the mechanical properties of actuators, a strain gradient should be introduced by regulating the molecular alignment; however, the miniaturization of polymer actuators for microscale systems has raised concerns regarding the complexity of such molecular control. Herein, a novel method for the fabrication of micro-actuators using a simple molecular self-alignment method is presented. Amphiphilic molecules that consist of azobenzene mesogens were located between the hydrophilic and hydrophobic surfaces, which resulted in a splayed alignment. Thereafter, molecular isomerization on the surface induced a large strain gradient and bending movement of the actuator under ultraviolet-light irradiation. Moreover, the microelectromechanical systems allowed for the variation of the actuator size below the micron scale. The mechanical properties of the fabricated actuators such as the bending direction, maximum angle, and response time were evaluated with respect to their thicknesses and lengths. The derivatives of the polymer actuator microstructure may contribute to the development of novel applications in the micro-robotics field.

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Rahim Mutlu ◽  
Gürsel Alıcı

In this paper, we report on a multistable linear actuation mechanism articulated with electroactive polymer actuators, widely known as artificial muscles. These actuators, which can operate both in wet and dry media under as small as 1.0 V potential difference, are fundamentally cantilever beams made of two electroactive polymer layers (polypyrrole) and a passive polyvinylidene fluoride substrate in between the electroactive layers. The mechanism considered is kinematically analogous to a four-bar mechanism with revolute-prismatic-revolute-prismatic pairs, converting the bending displacement of a polymer actuator into a rectilinear movement of an output point. The topology of the mechanism resembles that of bistable mechanisms operating under the buckling effect. However, the mechanism proposed in this paper can have many stable positions depending on the input voltage. After demonstrating the feasibility of the actuation concept using kinematic and finite element analyses of the mechanism, experiments were conducted on a real mechanism articulated with a multiple number (2, 4, or 8) of electroactive polymer actuators, which had dimensions of 12×2×0.17 mm3. The numerical and experimental results demonstrate that the angular displacement of the artificial muscles is accurately transformed into a rectilinear motion by the proposed mechanism. The higher the input voltage, the larger the rectilinear displacement. This study suggests that this multistable linear actuation mechanism can be used as a programmable switch and/or a pump in microelectromechanical systems (MEMS) by adjusting the input voltage and scaling down the mechanism further.


2014 ◽  
Vol 20 (6) ◽  
pp. 1841-1847 ◽  
Author(s):  
Fei Liu ◽  
Dan Wu ◽  
Ken Chen

AbstractMechanical properties are vital for living cells, and various models have been developed to study the mechanical behavior of cells. However, there is debate regarding whether a cell behaves more similarly to a “cortical shell – liquid core” structure (membrane-like) or a homogeneous solid (cytoskeleton-like) when experiencing stress by mechanical forces. Unlike most experimental methods, which concern the small-strain deformation of a cell, we focused on the mechanical behavior of a cell undergoing small to large strain by conducting microinjection experiments on zebrafish embryo cells. The power law with order of 1.5 between the injection force and the injection distance indicates that the cell behaves as a homogenous solid at small-strain deformation. The linear relation between the rupture force and the microinjector radius suggests that the embryo behaves as membrane-like when subjected to large-strain deformation. We also discuss the possible reasons causing the debate by analyzing the mechanical properties of F-actin filaments.


2012 ◽  
Vol 12 ◽  
pp. 149-156 ◽  
Author(s):  
Rameshwar Adhikari

The influence of the presence of uncoupled polystyrene-block-polybutadiene (SB) diblock chains to polystyrene-block-polybutadiene-block-polystyrene (SBS) triblock copolymers on the mechanical properties of the latter has been studied by means of tensile testing and dynamic mechanical analysis preparing several lamellae forming SBS/ SB blends through solution casting. The microphase-separated morphology of the samples was investigated by transmission electron microscopy. Both large strain deformation tensile deformation behaviour and viscoelastic properties of the SBS block copolymers were found to be affected appreciably by the presence of uncoupled SB diblock. The storage modulus of linear SBS was found to drop more sharply in the plateau region than for the radial SBS at the same SB content. At low SB content (up to 20 wt.-% for linear SBS and still higher for radial one), the overall tensile properties was not negatively influenced. On the whole, star block copolymers were found to be less sensitive towards the presence of diblock.DOI: http://dx.doi.org/10.3126/njst.v12i0.6493 Nepal Journal of Science and Technology 12 (2011) 149-156


2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhiming Hu ◽  
Wei Fang ◽  
Qunyang Li ◽  
Xi-Qiao Feng ◽  
Jiu-an Lv

AbstractRealizing programmable assembly and reconfiguration of small objects holds promise for technologically-significant applications in such fields as micromechanical systems, biomedical devices, and metamaterials. Although capillary forces have been successfully explored to assemble objects with specific shapes into ordered structures on the liquid surface, reconfiguring these assembled structures on demand remains a challenge. Here we report a strategy, bioinspired by Anurida maritima, to actively reconfigure assembled structures with well-defined selectivity, directionality, robustness, and restorability. This approach, taking advantage of optocapillarity induced by photodeformation of floating liquid crystal polymer actuators, not only achieves programmable and reconfigurable two-dimensional assembly, but also uniquely enables the formation of three-dimensional structures with tunable architectures and topologies across multiple fluid interfaces. This work demonstrates a versatile approach to tailor capillary interaction by optics, as well as a straightforward bottom-up fabrication platform for a wide range of applications.


2007 ◽  
Vol 539-543 ◽  
pp. 2787-2792 ◽  
Author(s):  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Jin Guo Li ◽  
Koichi Tsuchiya

Formation of nanocrystalline structure by severe plastic deformation has studied extensively. Although ultra fine grained structure (grain size larger than 100 nm) had been obtained in many processes such as heavy cold rolling, equal channel angular pressing (ECAP) or accumulative roll bonding (ARB), the formation of nano grained structure (< 100 nm) is limited to processes such as ball milling, shot peening or drilling. In the present study, high pressure torsion (HPT) deformation and drilling were carried out to understand the conditions necessary to obtain nano grained structure in steels. The results of HPT experiments in pure Fe showed that HPT has superior ability of strengthening and grain refinement probably due to a strain gradient but the saturation of grain refinement occurs before reaching nano grained structure. Drilling experiments in high carbon martensitic steel revelaed that nano grained ferrite forms at the drilled hole surface only when the transformation from ferrite to austenite takes place during drilling. Considering various other processes by which nano grained ferrite was produced, it is proposed that heavy strains with large strain gradients together with dynamic transformation are necessary to reach nano grained ferrite structure.


Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 846 ◽  
Author(s):  
Viacheslav Slesarenko ◽  
Seiji Engelkemier ◽  
Pavel Galich ◽  
Dmitry Vladimirsky ◽  
Gregory Klein ◽  
...  

The following is a study of the performance of soft cable-driven polymer actuators produced by multimaterial 3D printing. We demonstrate that the mechanical response of the polymer actuator with an embedded cable can be flexibly tuned through the targeted selection of actuator architecture. Various strategies, such as the addition of discrete or periodic stiff inserts, the sectioning of the actuator, or the shifting of the cable channel are employed to demonstrate ways to achieve more controllable deformed shape during weight lifting or reduce the required actuation force. To illustrate these concepts, we design and manufacture a prototype of the soft polymer gripper, which is capable of manipulating small, delicate objects. The explored strategies can be utilized in other types of soft actuators, employing, for instance, actuation by means of electroactive polymers.


2003 ◽  
Author(s):  
Akihiro Matsuda

This paper proposes a new numerical model of lead material to predict mechanical properties of isolation and vibration control devices using lead as damping material. Shear and tensile loading tests of lead were carried out to make the numerical model. Shear loading test specimen were constructed from a circumferential lead part welded at the top and bottom to steel flanges. Cyclic stress-strain relations in large strain region were obtained from shear loading test results. The elastic constants and the initial yield stress were given from tensile loading test results. Therefore a numerical model was made using both shear loading and tensile loading test results. Mechanical properties of lead dampers and isolated rubber bearings were simulated using the proposed numerical model via finite element method to show applicability of the model.


2019 ◽  
Vol 963 ◽  
pp. 305-308
Author(s):  
Jaweb Ben Messaoud ◽  
Jean François Michaud ◽  
Marcin Zielinski ◽  
Daniel Alquier

The silicon carbide cubic polytype (3C-SiC) is a material of choice to fabricate microelectromechanical systems. However, the mechanical properties of 3C-SiC-based devices are severely linked to the stress of the involved 3C-SiC material. Moreover, the stress level can hamper completing microsystems. As a consequence, in this study, we considered the influence of aluminum (Al) doping towards the mechanical properties of 3C-SiC epilayers and demonstrated a noticeable reduction of the Young’s modulus with a high Al incorporation.


2020 ◽  
Vol 178 ◽  
pp. 508-512 ◽  
Author(s):  
Jonathan G. Gigax ◽  
Osman El-Atwani ◽  
Quinn McCulloch ◽  
Berk Aytuna ◽  
Mert Efe ◽  
...  

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