Reversible Heat-Induced Microwrinkling of PEDOT:PSS Nanofilm Surface Over a Monodomain Liquid Crystal Elastomer

Greco, Francesco; Domenici, Valentina; Romiti, Stefano; Assaf, Tareq; Zupančič, Borut; Milavec, Jerneja; Zalar, Boštjan; Mazzolai, Barbara; Mattoli, Virgilio

doi:10.1080/15421406.2012.763208

Cited by 13 publications

(35 citation statements)

References 22 publications

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“…The presence of the wrinkles was confirmed through optical microscopy ( Figure a), and it was clear that the wrinkles always extend parallel to the alignment director of the underlying LC network. This is in contrast to previous research using a crosslinked LC network as the foundation, where the wrinkles always ran perpendicular to the alignment director when formed upon heating, or parallel to the director when formed upon cooling . In the latter cases, the anisotropic contraction of the LC network, which takes place parallel to the director upon heating, was responsible for the formation of wrinkles.…”

Section: Resultscontrasting

confidence: 95%

On‐Demand Wrinkling Patterns in Thin Metal Films Generated from Self‐Assembling Liquid Crystals

Haan

Leclère

Damman

et al. 2014

Adv Funct Materials

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1360 wileyonlinelibrary.com layers in combination with simple photomasks in a contactless process, [ 4,5 ] spontaneously generating unique wrinkling patterns in any arbitrarily complex fashion.Wrinkling can be induced in bilayer systems consisting of a thin fi lm of a relatively stiff material on top of a foundation of a softer material as a result of a strain mismatch between the layers, usually induced by mechanical or heat-driven deformation of the foundation or the top layer. It is a well-studied and well-understood process. [6][7][8][9] Many applications for wrinkled surfaces have been demonstrated, including preparation of superhydrophobic [ 10 ] and antifouling surfaces, [ 11 ] actuators, [ 12 ] alignment of living cells, [ 13 ] optical focusing, [ 14 ] fabrication of microlens arrays, [ 15 ] fabrication of patterned electrodes, [ 16 ] stretchable conductors, [ 17 ] and strain-sensitive diffraction gratings. [ 18 ] Achieving precise control over the wrinkling properties is vital for the further development of these applications. The amplitude and period of the wrinkles can be easily tuned by changing the thickness of the thin, stiff top layer, [ 19,20 ] and the preparation of homogeneously wrinkled surfaces is rather straightforward. [ 1,9,20,21 ] A limited number of patterns over small surface areas have been reported. [ 6,[22][23][24][25][26] However, it is desirable to introduce a fl exible method of generating complex wrinkle patterns on demand, scalable to cover large areas. We demonstrate the power of our method by generating intricate multidomain patterns and continuous circular structures including azimuthal, radial, and even higher complexity arrangements as examples, without the need of multiple master patterns and the possibility of rapidly switching between patterns with simple rearrangement of light source, polarizers, and masks. Results and DiscussionWe make our wrinkling patterns using photoalignment of polymerizable LCs. [ 27,28 ] Alignment cells were prepared by combining two glass plates coated with a linearly photopolymerizable polymer which was photoaligned by exposure to polarized ultraviolet light through a variety of photomasks (Figure 1 b,c). [ 4 ] The cells were fi lled with a mixture of polymerizable LCs (Figure 1 d) at 80 °C in the isotropic phase, and were photopolymerized at 60 °C in the nematic phase into a polymer fi lm having a glass transition temperature of around 45 °C. [ 4 ] The cell was opened by removing one of the glass plates, and a gold On-Demand Wrinkling Patterns in Thin Metal Films Generated from Self-Assembling Liquid Crystals Laurens T. de Haan , Philippe Leclère , Pascal Damman , Albertus P. H. J. Schenning , and Michael G. Debije * In this work, a new, universal method is described that uses the photopatterning of liquid crystals, which is accurately translated into a controlled, intricately wrinkled metal surface. Remarkably, the patterns have an oscillation in amplitude of the wrinkles. This rapid method allows generation of intricate multidomain patt...

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Section: Resultscontrasting

confidence: 95%

On‐Demand Wrinkling Patterns in Thin Metal Films Generated from Self‐Assembling Liquid Crystals

Haan

Leclère

Damman

et al. 2014

Adv Funct Materials

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“…A typical energy of the structure under study couples the elastic film's deformation to that of the NLCE which, in turn, accounts for the interaction between the nematic monomers with the polymeric matrix as [19]. The direction defining the director alignment (n ⊗ n) is shown in orange.…”

Section: The Energy Functionalmentioning

confidence: 99%

Variational modelling of nematic elastomer foundations

Cesana

Baldelli²

2018

Math. Models Methods Appl. Sci.

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We compute the Γ-limit of energy functionals describing mechanical systems composed of a thin nematic liquid crystal elastomer sustaining a homogeneous and isotropic elastic membrane. We work in the regime of infinitesimal displacements and model the orientation of the liquid crystal according to the order tensor theories of both Frank and De Gennes. We describe the asymptotic regime by analysing a family of functionals parametrised by the vanishing thickness of the membranes and the ratio of the elastic constants, establishing that, in the limit, the system is represented by a two-dimensional integral functional interpreted as a linear membrane on top of a nematic active foundation involving an effective De Gennes optic tensor which allows for low order states. The latter can suppress shear energy by formation of microstructure as well as act as a pre-strain transmitted by the foundation to the overlying film.

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“…Another field of research related to LCE composites concerns the preparation of bilayered or multilayered systems obtained by coupling monodomain LCE films, mainly prepared according to the “two-step” cross-linking procedure [35], and one or two layers of conductive materials deposited onto the top surface of LCEs. These bilayered (or multilayered) systems were the object of several experimental and theoretical works in the past six years [85,86,87,88,89,90,91,92,93,94,95]. Several new technological applications were explored in detail based on unique phenomena characterizing the LCE-based bilayer composites, such as bending actuation [85,87,89,91,92,93,94,95] and surface wrinkling [85,86,88,90,92,93,94], as described in the sections below.…”

Section: Lce-based Bilayer Compositesmentioning

confidence: 99%

“…The first bilayer LCE-systems were produced by depositing conductive nanostructured thin polymer layers on the top surface of standard polysiloxane-based LCE films (see the general schemes reported in Figure 15). Agrawal et al [90] used nanolayers of poly(styrene) (PS), while Domenici, Greco et al [86,87,88] chose the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conductive polymer.…”

Section: Lce-based Bilayer Compositesmentioning

confidence: 99%

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Nanostructured Composites Based on Liquid-Crystalline Elastomers

et al. 2018

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Liquid-crystalline elastomers (LCEs) are the object of many research investigations due to their reversible and controllable shape deformations, and their high potential for use in the field of soft robots and artificial muscles. This review focuses on recent studies about polymer composites based on LCEs and nanomaterials having different chemistry and morphology, with the aim of instilling new physical properties into LCEs. The synthesis, physico-chemical characterization, actuation properties, and applications of LCE-based composites reported in the literature are reviewed. Several cases are discussed: (1) the addition of various carbon nanomaterials to LCEs, from carbon black to carbon nanotubes, to the recent attempts to include graphene layers to enhance the thermo-mechanic properties of LCEs; (2) the use of various types of nanoparticles, such as ferroelectric ceramics, gold nanoparticles, conductive molybdenum-oxide nanowires, and magnetic iron-oxide nanoparticles, to induce electro-actuation, magnetic-actuation, or photo-actuation into the LCE-based composites; (3) the deposition on LCE surfaces of thin layers of conductive materials (i.e., conductive polymers and gold nanolayers) to produce bending actuation by applying on/off voltage cycles or surface-wrinkling phenomena in view of tunable optical applications. Some future perspectives of this field of soft materials conclude the review.

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Reversible Heat-Induced Microwrinkling of PEDOT:PSS Nanofilm Surface Over a Monodomain Liquid Crystal Elastomer

Cited by 13 publications

References 22 publications

On‐Demand Wrinkling Patterns in Thin Metal Films Generated from Self‐Assembling Liquid Crystals

On‐Demand Wrinkling Patterns in Thin Metal Films Generated from Self‐Assembling Liquid Crystals

Variational modelling of nematic elastomer foundations

Nanostructured Composites Based on Liquid-Crystalline Elastomers

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