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Special Issue "Polymeric Soft Actuators"

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: 31 May 2017

Special Issue Editor

Guest Editor
Prof. Dr. Leonid Ionov

Polymer Science, Fibers & Materials, College of Engineering, College of Family & Consumer Sciences, The University of Georgia, 303 Dawson Hall, 305 Sanford Dr, Athens, GA 30602, USA
Website | E-Mail
Phone: +1 706-542-4885
Interests: polymer synthesis and physico-chemical characterization of polymers; polymer actuators; thin films; fibers; biomaterial; energy storage; smart surfaces; biocatalysis; hydrogels; shape-memory polymers

Special Issue Information

Dear Colleagues,

This Special Issue of Polymers is dedicated to the polymeric actuating systems. Actuators are materials and devices, which are able to change their shape in response to a change in environmental conditions and, thus, perform mechanical work on nano, micro and marcoscales. Actuators find very broad application in microfabrication, microelectronics, medicine and lab-on-chip systems. Among the huge variety of different actuator materials, polymer-based ones are highly attractive due to a spectrum of different properties of polymers. The polymers can be soft (viscoelastic state) and hard (glassy state) depending on their chemical and physical structure that allows the design of soft actuators for handling of soft living tissues and hard actuators for handling of metals. There are many polymers sensitive to different stimuli that allows design of actuators, which can be controlled by temperature, pH, biosignals, light, etc. Many polymers are biocompatible and biodegradable that allows integration of polymeric actuators in living systems and their resorption there. The scope of this issue includes stimuli-responsive hydrogels, shape-memory polymers, liquid crystalline actuators and other polymeric actuating systems. Consequently, this Special Issue aims to reflect the current efforts and progress made in the field of polymeric actuators.

Prof. Dr. Leonid Ionov
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs).

Keywords

  • Polymeric actuators
  • Stimuli-responsive hydrogel
  • Shape-memory polymers
  • Liquid crystalline actuators

Published Papers (4 papers)

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Research

Open AccessArticle Influence of a Crosslinker Containing an Azo Group on the Actuation Properties of a Photoactuating LCE System
Polymers 2016, 8(12), 435; doi:10.3390/polym8120435
Received: 15 October 2016 / Revised: 6 December 2016 / Accepted: 8 December 2016 / Published: 14 December 2016
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Abstract
Photoactuating liquid crystalline elastomers (LCE) are promising candidates for an application as artificial muscles in microdevices. In this work, we demonstrate that by optimizing (1) the illumination conditions and (2) the mixture of azo monomer and azo crosslinker, thick films of an all-azo
[...] Read more.
Photoactuating liquid crystalline elastomers (LCE) are promising candidates for an application as artificial muscles in microdevices. In this work, we demonstrate that by optimizing (1) the illumination conditions and (2) the mixture of azo monomer and azo crosslinker, thick films of an all-azo LCE can be prepared, which show a strong length change without bending during photoactuation. This becomes possible by working with white light (about 440 nm), whose absorption is low, leading to a large penetration depth. By adding an azo crosslinker to a previously prepared system, several improvements of the actuation properties—like a stronger photoactuation at lower operational temperatures—could be achieved. In addition, films of different crosslinker concentrations and thicknesses were produced by photopolymerization at varying temperatures within a magnetic field, and their thermo- and photoresponsive behavior was investigated. An extraordinarily strong maximal thermal actuation of 46% and—by exposure to white light at 70 °C—a photoresponsive change in length of up to 40% in just about 13 s could be obtained. Even densely crosslinked samples were still able to photoactuate remarkably. Isothermal back-deformation could either be achieved by irradiation with red light (7 min) or by keeping the film in the dark (13 min). Full article
(This article belongs to the Special Issue Polymeric Soft Actuators)
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Figure 1

Open AccessArticle Water-Blown Polyurethane Foams Showing a Reversible Shape-Memory Effect
Polymers 2016, 8(12), 412; doi:10.3390/polym8120412
Received: 10 October 2016 / Revised: 14 November 2016 / Accepted: 18 November 2016 / Published: 28 November 2016
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Abstract
Water-blown polyurethane (PU) foams are of enormous technological interest as they are widely applied in various fields, i.e., consumer goods, medicine, automotive or aerospace industries. The discovery of the one-way shape-memory effect in PU foams provided a fresh impetus for extensive investigations on
[...] Read more.
Water-blown polyurethane (PU) foams are of enormous technological interest as they are widely applied in various fields, i.e., consumer goods, medicine, automotive or aerospace industries. The discovery of the one-way shape-memory effect in PU foams provided a fresh impetus for extensive investigations on porous polymeric actuators over the past decades. High expansion ratios during the shape-recovery are of special interest when big volume changes are required, for example to fill an aneurysm during micro-invasive surgery or save space during transportation. However, the need to program the foams before each operation cycle could be a drawback impeding the entry of shape-memory polymeric (SMP) foams to our daily life. Here, we showed that a reversible shape-memory effect (rSME) is achievable for polyurethane water-blown semicrystalline foams. We selected commercially available crystallizable poly(ε-caprolactone)-diols of different molecular weight for foams synthesis, followed by investigations of morphology, thermal, thermomechanical and shape-memory properties of obtained compositions. Densities of synthesized foams varied from 110 to 180 kg∙m−3, while peak melting temperatures were composition-dependent and changed from 36 to 47 °C, while the melting temperature interval was around 15 K. All semicrystalline foams exhibited excellent one-way SME with shape-fixity ratios slightly above 100% and shape-recovery ratios from the second cycle of 99%. The composition with broad distribution of molecular weights of poly(ε-caprolactone)-diols exhibited an rSME of about 12% upon cyclic heating and cooling from Tlow = 10 °C and Thigh = 47 °C. We anticipate that our experimental study opens a field of systematic investigation of rSMEs in porous polymeric materials on macro and micro scale and extend the application of water-blown polyurethane foams to, e.g., protective covers with zero thermal expansion or even cushions adjustable to a certain body shape. Full article
(This article belongs to the Special Issue Polymeric Soft Actuators)
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Open AccessArticle Microfluidic Synthesis of Actuating Microparticles from a Thiol-Ene Based Main-Chain Liquid Crystalline Elastomer
Polymers 2016, 8(12), 410; doi:10.3390/polym8120410
Received: 17 October 2016 / Revised: 10 November 2016 / Accepted: 16 November 2016 / Published: 25 November 2016
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Abstract
In this article the microfluidic synthesis of strongly actuating particles on the basis of a liquid crystalline main-chain elastomer is presented. The synthesis is carried out in a capillary-based co-flow microreactor by photo-initiated thiol-ene click chemistry of a liquid crystalline monomer mixture. These
[...] Read more.
In this article the microfluidic synthesis of strongly actuating particles on the basis of a liquid crystalline main-chain elastomer is presented. The synthesis is carried out in a capillary-based co-flow microreactor by photo-initiated thiol-ene click chemistry of a liquid crystalline monomer mixture. These microparticles exhibit a deformation from a spherical to a rod-like shape during the thermal-initiated phase transition of the liquid crystalline elastomer (LCE) at which the particles’ aspect ratio is almost doubled. Repeated contraction cycles confirm the complete reversibility of the particles’ actuation properties. The transition temperature of the LCE, the temperature range of the actuation process as well as the magnitude of the particles’ aspect ratio change are studied and controlled by the systematic variation of the liquid crystalline crosslinker content in the monomer mixture. Especially the variable actuation properties of these stimuli-responsive microparticles enable the possibility of an application as soft actuators or sensors. Full article
(This article belongs to the Special Issue Polymeric Soft Actuators)
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Open AccessArticle Fabrication of a Miniature Paper-Based Electroosmotic Actuator
Polymers 2016, 8(11), 400; doi:10.3390/polym8110400
Received: 25 September 2016 / Revised: 1 November 2016 / Accepted: 8 November 2016 / Published: 15 November 2016
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Abstract
A voltage-controlled hydraulic actuator is presented that employs electroosmotic fluid flow (EOF) in paper microchannels within an elastomeric structure. The microfluidic device was fabricated using a new benchtop lamination process. Flexible embedded electrodes were formed from a conductive carbon-silicone composite. The pores in
[...] Read more.
A voltage-controlled hydraulic actuator is presented that employs electroosmotic fluid flow (EOF) in paper microchannels within an elastomeric structure. The microfluidic device was fabricated using a new benchtop lamination process. Flexible embedded electrodes were formed from a conductive carbon-silicone composite. The pores in the layer of paper placed between the electrodes served as the microchannels for EOF, and the pumping fluid was propylene carbonate. A sealed fluid-filled chamber was formed by film-casting silicone to lay an actuating membrane over the pumping liquid. Hydraulic force generated by EOF caused the membrane to bulge by hundreds of micrometers within fractions of a second. Potential applications of these actuators include soft robots and biomedical devices. Full article
(This article belongs to the Special Issue Polymeric Soft Actuators)
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