We have developed patterned surfaces that control the thermal radiation without the use of controllers and power supplies. Ultralight patterned surfaces were designed to passively transform their geometry and change their effective emissivity as a function of temperature with the purpose of controlling the temperature of a satellite. These transformable patterned surfaces may consist of flat smaller arrays, passively reacting under temperature stimuli by reversibly transforming their geometry from 2D to 3D complex shapes. The transformation of the arrays conceals or reveals materials of different thermo-optical properties, while the view factor of the surface changes as well. Consequently, the entire emissivity function of a surface can be designed. The shape transformation is attributed to the anisotropic properties of a tri-layer material and to the coefficient of thermal expansion mismatch, which cause the patterns to transform at any temperature level. We developed a low-cost tri-layer material that has been optimized to achieve very large deformations within small temperature deviations. The emissivity of the patterned surface presents significant variation, namely Δε ≈ 0.7 within ΔΤ ≤ 40 °C. The weight of the smart surfaces is less than 330 gr/m~2 . The results are very promising because the degradation of the multilayer material of a unitary cell is negligible up to 78,000 thermal cycles. However, local degradation of the multilayer materials was observed near N ≈ 132,000 thermal cycles due to local imperfections. The predicted and measured emissivity functions that we obtained were used for the preliminary thermal design of a nano-satellite in order to re-calculate its temperature (worst hot- and cold-cases) while taking into consideration different scenarios. The temperature deviation of the nano-satellite, as well as the minimum temperature, had significantly improved. The proposed re-design will have an advantageous impact on the selection of the heaters and the energy demands of a nano-satellite.
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机译：我们开发了图案化表面，可控制热辐射而无需使用控制器和电源。以外的图案化表面被设计成被动地改变它们的几何形状，并随着温度的函数而改变其有效的发射率，目的是控制卫星的温度。这些可变形图案化表面可以由扁平较小的阵列组成，通过从2D到3D复杂形状可逆地将它们的几何形状变换为温度刺激而被动地反应。阵列的转换隐藏或揭示了不同热光学性质的材料，而表面的视图也是变化的。因此，可以设计表面的整个发射率函数。形状变换归因于三层材料的各向异性特性和热膨胀系数不匹配，这使得图案在任何温度水平处变换。我们开发了一种低成本的三层材料，已被优化，以在小温度偏差内实现非常大的变形。图案化表面的发射率存在显着的变化，即Δε≈0.7内ΔT≤40℃。智能表面的重量小于330 gr / m〜2。结果非常有前途，因为单层电池的多层材料的劣化可忽略不计，可忽略可忽略多达78,000个热循环。然而，由于局部缺陷，在N≈132,000的热循环附近观察到多层材料的局部劣化。我们获得的预测和测量的发射率函数用于纳米卫星的初步热设计，以便在考虑不同场景的同时重新计算其温度（最糟糕的热和冷型）。纳米卫星的温度偏差以及最小温度显着提高。所提出的重新设计将对选择加热器和纳米卫星的能量需求产生有利的影响。
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