Electrically tuning soft membranes to both a higher and a lower transparency

Chen, Leihao; Ghilardi, Michele; Busfield, James J. C.; Carpi, Federico

doi:10.1038/s41598-019-56505-9

Cited by 3 publications

(5 citation statements)

References 43 publications

(41 reference statements)

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“…Therefore, even non-conductive materials could have been chosen. However, in this work PEDOT:PSS was adopted to enable comparisons with a previous work of ours [14], where it had been used both as a scattering medium and as a deformable electrode.…”

Section: Methodsmentioning

confidence: 99%

“…The most used technologies for such optical devices consist of electrochromic materials [4][5][6] and polymerdispersed liquid crystals (PDLC) [7][8][9][10]. Recently, so-called dielectric elastomer actuators (DEAs) have been reported as a promising alternative technology to obtain voltage-induced large and continuous changes of the transparency of a soft surface [11][12][13][14][15][16][17][18][19]. Unlike electrochromic materials, where the operation is based on electrochemical reactions, the DEA technology relies on an electrostatic effect, which is therefore intrinsically faster [11][12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, so-called dielectric elastomer actuators (DEAs) have been reported as a promising alternative technology to obtain voltage-induced large and continuous changes of the transparency of a soft surface [11][12][13][14][15][16][17][18][19]. Unlike electrochromic materials, where the operation is based on electrochemical reactions, the DEA technology relies on an electrostatic effect, which is therefore intrinsically faster [11][12][13][14][15][16][17][18][19]. In comparison with PDLC materials, which only offer on-off switching capabilities, DEA-based devices allow for the transparency to be controlled over continuous ranges [11][12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…Unlike electrochromic materials, where the operation is based on electrochemical reactions, the DEA technology relies on an electrostatic effect, which is therefore intrinsically faster [11][12][13][14][15][16][17][18][19]. In comparison with PDLC materials, which only offer on-off switching capabilities, DEA-based devices allow for the transparency to be controlled over continuous ranges [11][12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…In a first strategy, a DE membrane is made translucent with wrinkled stretchable transparent electrodes, whose transparency can be increased by voltage-induced surface expansions that flatten the wrinkles [11][12][13]. The second strategy combines the previous concept with a compression of the membrane by an outer annular DEA, so as to obtain a dual-operation device, whose transparency can be both increased and decreased, depending on whether the electrical activation is used to generate a membrane expansion or contraction [14]. The third strategy uses transparent electrodes that cover a DE membrane fixed to a rigid glass substrate, whose transparency can be reduced by very high electric fields, which create microscopic craters on the surface, due to electromechanical instabilities [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

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Electrically tunable directional light scattering from soft thin membranes

2020

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The possibility of electrically tuning the scattering of light from surfaces by dynamically varying their properties is desirable for controllable transparency devices and diffusion filters. As a difference from state-of-the-art approaches where scattering is changed isotropically, this paper presents the first smart-material-based technology enabling electrical modulations in a single or multiple directions, which can be selected dynamically. The effect is achieved from thin soft membranes with transparent PEDOT:PSS coatings, which are electrically deformed along a single or multiple axes, using dielectric elastomer actuation. Anisotropic scattering is induced by electrically tuning the formation of directional surface wrinkles. As a proof of concept, a bi-directional device is obtained by overlapping two 90°-shifted mono-directional layers that can be controlled independently. According to the activation of the layers, light can be scattered along either direction, as well as both of them. Prototypes made of an acrylic elastomer were demonstrated with mono-and bi-directional operations. Devices with a window-to-total area ratio of 1:4 also showed a maximum electrical reduction of optical transmittance from 75% to 4%. This functionality and possible extensions to more than two controllable directions suggest applicability as electrically controllable anisotropic light diffusers for dynamic light shaping, as well as tunable transparency surfaces.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrically tunable directional light scattering from soft thin membranes

2020

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Water Induced Reversible Switching of Optical Transparency of an Elastomer-Hydrogel Based Two-Phase Composite

Kuhar,

Ghatak

2024

ACS Appl. Opt. Mater.

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Dynamically tunable optical transparency has many applications: smart windows, camouflage coatings, sensors, and displays. To this end, switchable optical properties of complex materials like metamaterials and nanostructured surfaces, induced essentially via scattering, refraction, and reflection of light, have been explored extensively. However, the cost of making these materials and their complex design limit their applications. To address this need, we have presented a two-phase composite (TPC) material in which a hydrogel, e.g., gelatin, is dispersed as particles in a continuous medium of poly(dimethylsiloxane) (PDMS). Reversible switching of optical transparency is achieved by selective swelling of the embedded gelatin phase inside a pool of water and deswelling it by drying. In essence, an aqueous solution of gelatin is dispersed as fine droplets in a pool of PDMS oligomers mixed with its curing agent (elastomeric phase) and is then cured. The cured film turns opaque. When immersed in water for long enough, water diffuses through silicone and gets absorbed by gelatin. At this, gelatin swells with a consequent change in transparency. The rate of change in transparency is found to be a function of gelatin loading in the TPC material, gelatin drop size, and the thickness of the film. Within a certain parameter range, this rate turns more pronounced than would have been expected for simple Fickian diffusion of water through the film.

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Emerging tunable window technologies for active transparency tuning

Shrestha

Lau

Bastola

et al. 2022

Applied Physics Reviews

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Most modern high-rise buildings' facades use glasses for esthetics, daylight, and better environmental view through them. However, with the increasing use of a larger area of transparent glasses as walls, the visual privacy preservation of the indoors and heat energy loss through the windows are becoming a rising concern. Recent studies showed that nearly half of the energy consumed in a building goes to heating and air conditioning while approximately 40% of this energy is lost through windows. Windows with tunable optical properties that are generically termed “tunable windows or smart windows or switchable glass” are perceived as a potential solution for these problems. An optically tunable window can adjust the amount of daylighting passing through it, control the heat radiation, and/or change the transparency of the glasses for visual privacy preservation of indoors. Electrochromic glasses, polymer dispersed liquid crystal glasses, and suspended particle devices are available as commercial tunable windows but their high cost, limited optical performance, reliability, and operational complexity are hindering the widespread adaptation. Therefore, several other technologies for low-cost actively tunable windows capable of actively adjusting transparency are increasingly explored. However, most of such new technologies, working based on various optical principles, do not fulfill all the requirements of tunable windows. For instance, some can tune optical transmittance but do not affect energy transmission, and some can adjust heat radiation transmission but has a limited change in visual appearances. To fully take the advantage of the strengths as well as recognize the limitations of such emerging technologies, their optical principles need to be understood in-depth. Here, we review the recent developments in transmittance tunable windows by categorizing them based on the optics involved, namely, light absorption, reflection, and scattering. This in-depth review comprehensively discusses how the tunable window technologies compare to each other and offers insight into how their performance can be improved in the future.

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Electrically tuning soft membranes to both a higher and a lower transparency

Cited by 3 publications

References 43 publications

Electrically tunable directional light scattering from soft thin membranes

Electrically tunable directional light scattering from soft thin membranes

Water Induced Reversible Switching of Optical Transparency of an Elastomer-Hydrogel Based Two-Phase Composite

Emerging tunable window technologies for active transparency tuning

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