Direct Laser Writing of Four-Dimensional Structural Color Microactuators Using a Photonic Photoresist

Pozo, Marc del; Delaney, Colm; Bastiaansen, Cees W. M.; Diamond, Dermot; Schenning, Albert P. H. J.; Florea, Larisa

doi:10.1021/acsnano.0c02481

Cited by 104 publications

(108 citation statements)

References 46 publications

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“…Recently, hydrogel photoresists have been used for tunable photonic devices. Marc et al 50 used a cholesteric liquid crystals (LC)-based hydrogel resist to change colours at microscale. In their work, colours were tuned within a limited range by changing the intrinsic periodicity of chiral LC.…”

Section: Introductionmentioning

confidence: 99%

Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers

et al. 2021

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Four-dimensional (4D) printing of shape memory polymer (SMP) imparts time responsive properties to 3D structures. Here, we explore 4D printing of a SMP in the submicron length scale, extending its applications to nanophononics. We report a new SMP photoresist based on Vero Clear achieving print features at a resolution of ~300 nm half pitch using two-photon polymerization lithography (TPL). Prints consisting of grids with size-tunable multi-colours enabled the study of shape memory effects to achieve large visual shifts through nanoscale structure deformation. As the nanostructures are flattened, the colours and printed information become invisible. Remarkably, the shape memory effect recovers the original surface morphology of the nanostructures along with its structural colour within seconds of heating above its glass transition temperature. The high-resolution printing and excellent reversibility in both microtopography and optical properties promises a platform for temperature-sensitive labels, information hiding for anti-counterfeiting, and tunable photonic devices.

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Section: Introductionmentioning

confidence: 99%

Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers

et al. 2021

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“…As shown in prior research, below 40 RH%, no significant shift in the reflection band occurs. [ 31,34 ] The same effect can be achieved by maintaining a constant humidity level and lowering the temperature (see Figure 4c and Video S2, Supporting Information). This shift relies on the condensation of water into the flakes.…”

Section: Resultsmentioning

confidence: 77%

“…From past work, it is known that these color shifts are directly related to the physical swelling and deswelling of the polymer network. [ 9,31 ] As confirmed using circular polarized UV–vis measurements, the cholesteric LC (ChLC) retains most of its characteristic circular dichroism, and SEM images indicate molecular order and internal structural integrity is maintained in all states from the pristine film to the swollen polymer salt (Figure S2 and S3, Supporting Information). From the UV–vis data in Figure S3, Supporting Information, narrowing of the reflection bands is seen, an effect resulting from the loss of birefringence during formation of the polymer salt.…”

Section: Resultsmentioning

confidence: 93%

“…As shown in Figure S4, Supporting Information, the wavelength shift when changing the relative humidity level follows see an linear trend, while changing the temperature at constant relative humidity shows an exponential curve. [ 31 ]…”

Section: Resultsmentioning

confidence: 99%

“…Optical characteristics were measured with a PerkinElmer Lambda 750, a Shimadzu UV‐3012 PC fitted with linear polarizer‐ λ /4 waveplate stack for circular dichroism measurements, and an OceanOptics HR2000+ optical microscope‐attached photospectrometer for in situ measurements. During these in situ measurements, the microscope is operated in bright‐field reflection mode with the sample between crossed polarizers as explained in the study by del Pozo et al [ 31 ] SEM photographs were recorded by sputter‐coating material with Au and subsequently imaging it using a FEI Quanta 3D scanning electron microscope.…”

Section: Methodsmentioning

confidence: 99%

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Responsive Photonic Liquid Crystalline Flakes Produced by Ultrasonication

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Puig

et al. 2021

Advanced Photonics Research

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Responsive materials that alter their color in response to environmental changes can be used as optical sensors. Chiral nematic liquid crystals are photonic materials that selectively reflect specific wavelengths of light and have been made environmentally responsive. Herein, the use of ultrasonication of responsive cholesteric liquid‐crystal network films to form structurally colored flakes that demonstrate color changes when moved from an aqueous to dry environment and back again is demonstrated, which suggests a scalable technique to form quantities of responsive particles that could conceivably be embedded in permeable hosts to allow the optical detection of humidity or certain chemical species.

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4D Chiral Photonic Actuators with Switchable Hyper‐Reflectivity

Zhang

Zhou

Haan

et al. 2020

Adv Funct Materials

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Cholesteric liquid crystals (CLCs) are chiral photonic materials reflecting only circularly polarized light with the same handedness as the helical polymer structure. Concurrent shape and color changes can be achieved using CLCs, but the fabrication of CLCs with switchable 3D shape, structural color, and hyper‐reflectivity, that is, reflecting both left‐ and right‐handed circularly polarized light simultaneously, has not yet been achieved. Here, CLC elastomer (CLCE) actuators are reported to reflect equal amounts of left‐ and right‐handed circularly polarized light. Hyper‐reflectivity is achieved by uniaxially stretching the partially crosslinked film to induce helix deformation which is then fully crosslinked to fix the deformed helical structure. The shape, structural color, and hyper‐reflectivity of the polymer film are switchable with temperature. At high temperatures, only right‐handed circularly polarized light is reflected and the color is redshifted. The film can be shaped in three dimensions: a structural colored 3D shaped beetle is fabricated using molding, which reflects both left‐ and right‐handed circularly polarized light and shows reversible, temperature responsive structural color and 3D shape changes. Hence, 4D engineered bioinspired multifunctional materials are fabricated, which are interesting for applications ranging from sensing actuators to switchable hyper‐reflective films and objects.

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Direct Laser Writing of Four-Dimensional Structural Color Microactuators Using a Photonic Photoresist

Cited by 104 publications

References 46 publications

Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers

Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers

Responsive Photonic Liquid Crystalline Flakes Produced by Ultrasonication

4D Chiral Photonic Actuators with Switchable Hyper‐Reflectivity

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