Transformed Fourier and Fick equations for the control of heat and mass diffusion

Guenneau, Sébastien; Petiteau, David; Zerrad, Myriam; Amra, Claude; Puvirajesinghe, Tania M.

doi:10.1063/1.4917492

Cited by 60 publications

(32 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our mother nature offers countless animals, such as chameleons, stick insects, and some spiders, cuttlefish and octopuses, etc., which possess amazing color‐changing capabilities to create optical/thermal illusions to camouflage themselves against the environment for disguise, protection, hunting, or species reproduction . Inspired by such illusion phenomena, man‐made optical/thermal illusions have witnessed significant progress by resorting to artificially structured inhomogeneous metamaterials or metasurfaces, and the concept of illusion optics is proposed thereby . Nevertheless, two long‐standing challenges remain formidable.…”

Section: Materials Details Of Each Triangle In the First Quadrantmentioning

confidence: 99%

Illusion Thermotics

et al. 2018

View full text Add to dashboard Cite

"Fata Morgana" or "Mirage" phenomena have long been captivated as optical illusions, which actually relies on gradient-density air or vapor. Man-made optical illusions have witnessed significant progress by resorting to artificially structured metamaterials. Nevertheless, two long-standing challenges remain formidable: first, exotic parameters (negative or less than unity) become inevitable; second, the signature of original object is altered to that of a virtual counterpart. It is thus not able to address the holy grail of illusion per se, since a single virtual object still exposes the location. In this study, those problems are successfully addressed in a particular setup-illusion thermotics, which identically mimics the exterior thermal behavior of an equivalent reference and splits the interior original heat source into many virtual signatures. A general paradigm to design thermal illusion metadevices is proposed to manipulate thermal conduction, and empower robust simultaneous functions of moving, shaping, rotating, and splitting heat sources of arbitrary cross sections. The temperature profile inside the thermal metadevice can mislead the awareness of the real location, shape, size, and number of the actual heat sources. The present concept may trigger unprecedented development in other physical fields to realize multiple functionalized illusions in optics, electromagnetics, etc.

show abstract

Section: Materials Details Of Each Triangle In the First Quadrantmentioning

confidence: 99%

Illusion Thermotics

et al. 2018

View full text Add to dashboard Cite

show abstract

“…A related design based on piecewise homogeneous anisotropic regions has recently been discussed in the context of transient thermal carpet cloaking. [ 19 ] Nevertheless, for diffuse-light invisibility cloaks, one could successfully approximate laminates by simple piecewise homogeneous and isotropic regions. For example, mathematically, a cylindrical cloak designed by transformation optics leads to infi nitely many alternating concentric layers of high and low diffusivity, graded along the radial coordinate.…”

Section: Full Paper Full Paper Full Papermentioning

confidence: 99%

Cloaking Contacts on Large‐Area Organic Light‐Emitting Diodes

Mayer

Schittny

Egel

et al. 2016

Advanced Optical Materials

View full text Add to dashboard Cite

In this paper, we suggest a feasible way to homogenize the OLED light emission, i.e., to cloak the contacts or to make them "invisible" in emission. This task is schematically illustrated in Figure 1 . At fi rst sight, this task may appear the same as that of cloaking contact grids on the sunfacing side of solar cells. [ 8 ] These devices for solar cells operate in the regime of ballistic light propagation. [ 8 ] In sharp contrast, the cloaking devices for OLEDs described in the present paper operate in the distinct regime of multiple light scattering.We start in Section 2 by discussing two different blueprints based on the light-diffusion equation. The fi rst blueprint is based on coordinate transformations, leading to piecewise homogeneous and anisotropic diffusivities, the second blueprint uses piecewise homogeneous and isotropic diffusivities. The latter is postoptimized in Section 3 for large light throughput by using Monte-Carlo simulations, which can cover the regime between diffusive and ballistic light transport. Finally, the outcome is validated by model experiments in Section 4. Numerical Calculations Based on Light-Diffusion TheoryFigure 2 a illustrates the geometry of the problem considered in this paper. A homogeneous layer (yellow) emits light from its surface according to a Lambertian angular distribution. We assume that this layer is thin compared to all other dimensions.Metallic contact grids on top of large-area organic light-emitting diodes (OLEDs) are important for laterally homogenized current spreading leading to a lower series resistance and reduced large-scale brightness gradients. However, the contacts are also visible by unwanted shadows, i.e., by spatially inhomogeneous Lambertian light emission. In this paper, inspired by recent work on diffuse-light core-shell invisibility cloaking, a practical tailored distribution of light scattering centers is designed on top of an OLED to homogenize its light emission. Numerical solutions of the light-diffusion equation as well as Monte Carlo ray-tracing simulations are presented. The blueprint is verifi ed by experiments on a scaled-up model structure. The contacts can be made "invisible" in emission while maintaining large light throughput.

show abstract

“…On these pioneering works'heels, cloak is expanded to other fields like thermodynamics, [6][7][8] elastodynamics, 9,10 acoustics, 11,12 and particle diffusion. 13,14 Thermal cloak can thermally camouflage an object by means of regulating the heat flux that flows around an "invisible"region. 15,16 For one thing, a thermal detector outside the cloak cannot perceive the object from measuring the variation of background thermal field.…”

Section: Introductionmentioning

confidence: 99%

A Reverse Thermal Cloak Design Method Based on Inverse Problem Theory

Guo¹,

Qu²,

Wang³

2020

ES Energy Environ.

View full text Add to dashboard Cite

A reverse thermal cloak design method is developed based on inverse problem theory. The design of thermal conductivity distribution within a cloak can be regarded as the density-based topology optimization with that penalization parameter equals to 1. The relative density is explored using conjugate gradient method with an adjoint equation (CGMAE). A prescribed objective function is used to evaluate the design result, and the function is no larger than 6.41×10-6. The maximum deviation between background temperature with and without cloak position is no larger than 0.9% for background with uniform gradient and no larger than 5% for background with non-uniform gradient. The dimension of a cloak can also be designed in case of known material thermal conductivity to avoid complex material synthesis process. Compared with coordinate transformation, the reverse design method is able to remove anisotropy of thermal conductivity and is appropriate for design of irregularly shaped cloak. It is easy to implement programming for proposed method and can boost the flexibility of cloak design. Thus, the proposed method offers a practicable scheme for thermal cloak design to control heat conduction at will.

show abstract

Transformed Fourier and Fick equations for the control of heat and mass diffusion

Cited by 60 publications

References 31 publications

Illusion Thermotics

Illusion Thermotics

Cloaking Contacts on Large‐Area Organic Light‐Emitting Diodes

A Reverse Thermal Cloak Design Method Based on Inverse Problem Theory

Contact Info

Product

Resources

About