Nanoimprint Lithography on Silica Sol–Gels: A Simple Route to Sequential Patterning

Péroz, Christophe; Chauveau, Vanessa; Barthel, Étienne; Sondergard, E.

doi:10.1002/adma.200702484

Cited by 78 publications

(66 citation statements)

References 16 publications

(24 reference statements)

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“…Alternatively, photolithography-free patterning methods, such as nanoimprint (35), and LangmuirBlodgett assembly and etching (36), may be used to fabricate silica photonic crystals and microstructures in general at lower cost and larger scales. Moreover, although we have realized a visibly transparent thermal blackbody with the use of a silica photonic crystal, there are likely other approaches to achieving the same functionality, including multilayer dielectric coatings, that are even more cost-effective for large-scale fabrication.…”

Section: Discussionmentioning

confidence: 99%

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

Zhu

Raman

Fan

2015

Proc. Natl. Acad. Sci. U.S.A.

495

351

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A solar absorber, under the sun, is heated up by sunlight. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic for either operational or aesthetic considerations, but the resulting heating is undesirable. Because a solar absorber by necessity faces the sky, it also naturally has radiative access to the coldness of the universe. Therefore, in these applications it would be very attractive to directly use the sky as a heat sink while preserving solar absorption properties. Here we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal. When placed on a silicon absorber under sunlight, such a blackbody preserves or even slightly enhances sunlight absorption, but reduces the temperature of the underlying silicon absorber by as much as 13°C due to radiative cooling. Our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities.radiative cooling | thermal radiation | photonic crystal | solar absorber T he universe, at a temperature of 3 K, represents a significant renewable thermodynamic resource: it is the ultimate heat sink. Over midinfrared wavelengths, in particular between 8 and 13 μm, Earth's atmosphere is remarkably transparent to electromagnetic radiation. This wavelength range coincides with the peak wavelength of thermal radiation from terrestrial structures at typical ambient temperatures. Thus, a sky-facing terrestrial object can have radiative access to the universe. Exploiting this radiative access has led to the demonstration of radiative cooling (1-7), as well as proposals for direct electric power generation from thermal radiation of terrestrial objects (8).Whereas historically radiative cooling was largely developed for night-time applications (1-6, 9-13), recent works have achieved daytime radiative cooling (7,14). In particular, it was shown that the radiative cooling to below ambient air temperature can be achieved (7), with a photonic structure that reflects almost all incident sunlight and simultaneously emits significant thermal radiation in the midinfrared. Such a structure, being a near-perfect solar reflector, makes no use of incident sunlight. On the other hand, in many applications, including solar cells (15) and outdoor structures (16), the utilization of sunlight through absorption is intrinsic for either operational or aesthetic considerations, but the heating associated with sunlight absorption is undesirable. For these applications, lowering operating temperatures via radiative cooling is only viable if one can simultaneously preserve the absorption of sunlight.Here we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal, using a thermophotonic approach (17-30). When placed on a silicon absorber under sunlight, such a blackbody preserves and even slightly enhances sunlight absorption, but reduces the temperature of the silicon absorber by as m...

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Section: Discussionmentioning

confidence: 99%

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

Zhu

Raman

Fan

2015

Proc. Natl. Acad. Sci. U.S.A.

495

351

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“…Nanoimprint lithography ͑NIL͒ potentially fulfills these requirements. [4][5][6][7][8][9] When pressing a textured mold onto a soft film ͑resist͒ deposited on the surface, the film material flows into the mask features. If the system is crosslinked or quenched before the mold is released, permanent surface features are obtained.…”

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confidence: 99%

Confinement and flow dynamics in thin polymer films for nanoimprint lithography

Teisseire

Revaux

Foresti

et al. 2011

Applied Physics Letters

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In nanoimprint lithography (NIL) viscous flow in polymeric thin films is the primary mechanism for the generation and the relaxation of the structures. Here we quantify the impact of confinement on the flow rate. Pattern relaxation experiments were carried out above the glass transition temperature as a function of film thickness. The results are adequately fitted by a simple expression for the flow rate valid at all confinements. This expression, based on Newtonian viscosity, should be of use in NIL process design and for the measurement of the rheological properties of confined polymers.

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“…The dimensions necessary for daylighting applications also pose a challenge, requiring a period of 400 nm, an aspect ratio of 2 · h∕Λ 1.75, and transparency of the material. To fulfill these demands, the simple and low-cost SSGNIL [25,26] process is used to imprint nanometric patterns in a thin film on glass. In particular, the chosen sol-gel material has two principal advantages: its optical properties are similar to glass (refractive index 1.45) and it has a strong adhesion to glass substrates.…”

Section: Nanoimprint Fabricationmentioning

confidence: 99%

Controlled angular redirection of light via nanoimprinted disordered gratings

et al. 2013

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Enhanced control of diffraction through transparent substrates is achieved via disordered gratings in a silica sol-gel film. Tailoring the degree of disorder allows tuning of the diffractive behavior from discrete orders into broad distributions over large angular range. Gratings of optical quality are formed by silica sol-gel nanoimprint lithography and an optical setup for the measurement of continuous diffraction patterns is presented. Sound agreement is found between measurements and simulation, validating both the approach for redirection of light and the fabrication process. The disordered gratings are presented in the context of improved interior daylighting and may furthermore be suited to a wide variety of applications where controlled angular redirection of light is desired.

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Nanoimprint Lithography on Silica Sol–Gels: A Simple Route to Sequential Patterning

Cited by 78 publications

References 16 publications

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

Confinement and flow dynamics in thin polymer films for nanoimprint lithography

Controlled angular redirection of light via nanoimprinted disordered gratings

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