科学技術の発展に伴い、膜材料生体模倣フィルム産業も継続的に進歩しています。 More and more new functional membranes are constantly appearing, which brings more convenience to our lives. Recently, Shanghai Jiaotong University has developed a new type of flexible film. Here, Xinst will show you what kind of changes this film can bring to people's lives!

Summer is hot, the most comfortable thing for people is to eat iced watermelon in the air-conditioned room. Whether it is a cool room or a chilled watermelon, refrigeration technology is required. Most existing refrigeration technologies are based on vapor compression refrigeration, which requires the use of refrigerants with potential environmental pollution on the one hand and the consumption of large amounts of electricity on the other.

According to statistics, China's building energy consumption accounts for about 35% of the country's total energy consumption, and the cooling and air conditioning system's energy consumption accounts for about 50 to 60% of the building's energy consumption. Therefore, refrigeration technology has become a major energy consumer, and the technology needs to be updated. . In nature, some organisms have a special surface structure, and through passive radiation, show amazing thermal regulation ability. It is undoubtedly a promising technology to learn nature, prepare special surface structures, and realize passive radiation cooling.

A few days ago, the team of Professor Zhou Han and Professor Fan Tongxiang of Shanghai Jiaotong University and their collaborators discovered that the multi-level micro-nano structure of the long horn beetle (Neocerambyx Gigas) wings shows excellent temperature regulation ability, and then based on the new photomask Method, bionic preparation of a flexible film with a similar structure to achieve passive radiation cooling, at the same time, this technology also realizes the macro preparation of radiation cooling film. Related work was published in "PNAS" as "Biologically inspired flexible photonic films for efficient passive radiative cooling".

Morphology and thermal regulation mechanism of the long-wing beetle

A long-horned beetle lives in volcanic areas in Indonesia and Thailand. The temperature where it lives usually rises to above 40°C (104°F) in summer, and the ground temperature can reach 70°C (158°F). These long-horned beetles have attracted much attention from researchers due to their ability to resist heat and regulate heat.

The researchers first observed the microstructure of the long wing beetle's front wing, and found that the surface of the front wing was covered with fluff, with a density of more than 25,500 per square centimeter. The color of the front wing can also effectively resist the fading treatment, showing the structural color characteristics of the photonic crystal. Further observation revealed that each fluff is a triangular structure composed of two smooth surfaces and a rough surface. The rough surface is a corrugated structure with a width of 1 μm and a height of 0.18 μm, which together with the fluff itself constitutes a multi-level rough structure.

The optical properties and temperature adjustment capabilities of the long-horn beetle's front wing (a) the reflection of the front wing in the visible-near infrared spectral range; (b) the change in the reflectance of the front wing under different ethanol conditions; (cd) the visible-near infrared light Enter the reflection from different directions of the fluff; (e) the ratio of the absorption and reflected light ratio of the front wing in the mid-infrared region with the wavelength; (f) the change of the reflectance of the fluff at different incident angles; (gh) the front wing in vacuum and air The surface temperature changes with (red) and without (black) fluff.

After grasping the microstructure of the surface of the front wing, the researchers studied the optical properties and temperature adjustment capabilities. First of all, the researchers studied the reflection of the front wings with or without fluff, and found that the presence of fluff can increase the light reflectance by more than 35%, and through the immersion experiment of ethanol solution, it was further determined that high reflectance is a benefit Multi-level microstructure existing on the surface. In order to further explore the mechanism principle, the researchers used time-domain finite difference simulation to study the optical characteristics of multi-level microstructures at different incident angles. The optics entering from a side of the triangular corrugated surface with a small incident angle will undergo total internal reflection. At the same time, when the wavelength of the incident light is similar to the ripple width, it will generate strong Mie scattering, so that it has a strong reflectivity at all incident angles. The absorption/emission rate on the surface of the front wing covered with fluff reaches 0.94, which indicates that the beetle dissipates the body's heat well. The time-temperature curve also shows that in the presence of surface fluff, a significant cooling effect can reach 3.2 ℃ and 1.5 ℃ temperature drops in vacuum and air, respectively. This excellent temperature control ability is beneficial for insects to carry out daily foraging activities in high temperature and sun exposure environments.

バイオニックフィルムの調製と特性評価

カミキリムシの表面構造と温度制御能力の研究に基づいて、研究者たちは同様の構造のバイオニック放射冷却フィルムをバイオニックで準備し、放射冷却制御を達成しようとしました。

バイオミメティックフィルムの調製と形態学的特徴 （A）テンプレートとバイオニックフィルムの準備プロセス。 （bc）シリコンテンプレートとフィルムの走査型電子顕微鏡写真。 （d）バイオニックフィルムのマクロ写真。 （e）バイオニックフィルムの冷却原理の概略図。 （f）バイオニックフィルムの断面スキャン電子顕微鏡写真。

In the preparation process, firstly, a silicon template with a triangular structure is prepared by photolithography, and then a precursor solution containing silicone and alumina microspheres is spin-coated on the surface of the template. After thermal polymerization, the surface is separated into a triangular structure. Structured film. This method can achieve large-scale, large-scale preparation of the film, and has certain versatility. It can achieve the doping of various ceramic particles such as zinc oxide, zirconium oxide, magnesium oxide, and titanium dioxide.

バイオニック生体模倣フィルムフィルムの光学的性質とその放射冷却能力。 （A）バイオニックフィルム（黒）とスムースフィルム（赤）の放射効率。 （b）TASWでシミュレートされた平均吸収率と放射率の比率。 （c）輻射熱放散性能の測定装置の図。 （d）バイオニックフィルムと気温; （e）バイオニックフィルムによって引き起こされる温度低下。 （fh）時間の経過に伴う測定プロセス中の太陽光強度（f）、相対湿度（g）、および熱放散電力（h）。

生体模倣フィルムを入手した後、研究者はその性能をテストし、その結果、太陽スペクトル範囲での平均反射率は約95％であり、TASWの平均放射率は> 0.96であり、滑らかなフィルムの放射率と比較されました。大幅に改善されました。 次に、フィルムの実際の冷却能力を評価しました。 平均太陽強度が約862W・m-2、湿度が22.7％の条件下で、バイオニックフィルムの平均温度は5.1°Cに下がり、最高温度は7°Cに下がりました。生体模倣フィルムは、それ自体を冷却するだけでなく、周囲の環境やフィルムで覆われている機器や加熱体の温度を大幅に下げることができます。

The biomimetic film can not only achieve radiant cooling but also other functions at the same time. For example, due to the low surface energy of silicone rubber combined with the micro-nano-level rough surface of the film, the film also has the ability of super-hydrophobic and self-cleaning. Researchers have also applied this kind of bionic radiation cooling film to wearable devices, personal electronic devices, automobiles and other devices, which have shown good cooling effects.

研究者たちは、カミキリムシの微細構造を研究することにより、温度制御の原理を探求しました。 次に、この原理に基づいて、平均温度降下が5℃を超えるパッシブ放射冷却を実現するために、柔軟なバイオニックフィルムを作成しました。 同時に、このバイオニックフィルムの柔軟性と疎水性は、さまざまなウェアラブルデバイス、電子デバイス、および車両への適用の基礎を築きました。 このパッシブ放射冷却温度調節技術は、間違いなく、より省エネで環境に優しいものです。 この作業はまた、高性能フォトンラジエーターに基づく放射冷却技術のその後の大量生産への道を開いた。