Biologically inspired flexible photonic films for efficient passive radiative cooling

Abstract

<jats:p>Temperature is a fundamental parameter for all forms of lives. Natural evolution has resulted in organisms which have excellent thermoregulation capabilities in extreme climates. Bioinspired materials that mimic biological solution for thermoregulation have proven promising for passive radiative cooling. However, scalable production of artificial photonic radiators with complex structures, outstanding properties, high throughput, and low cost is still challenging. Herein, we design and demonstrate biologically inspired photonic materials for passive radiative cooling, after discovery of longicorn beetles’ excellent thermoregulatory function with their dual-scale fluffs. The natural fluffs exhibit a finely structured triangular cross-section with two thermoregulatory effects which effectively reflects sunlight and emits thermal radiation, thereby decreasing the beetles’ body temperature. Inspired by the finding, a photonic film consisting of a micropyramid-arrayed polymer matrix with random ceramic particles is fabricated with high throughput. The film reflects ∼95% of solar irradiance and exhibits an infrared emissivity &gt;0.96. The effective cooling power is found to be ∼90.8 W⋅m<jats:sup>−2</jats:sup>and a temperature decrease of up to 5.1 °C is recorded under direct sunlight. Additionally, the film exhibits hydrophobicity, superior flexibility, and strong mechanical strength, which is promising for thermal management in various electronic devices and wearable products. Our work paves the way for designing and fabrication of high-performance thermal regulation materials.</jats:p>

Thermal Metamaterial: Fundamental, Application, and Outlook

“…Particularly, biologically inspired photonic films were also reported successively. The efficient radiative-cooling photonic crystal structures of Saharan silver ants ( Shi et al., 2015 ) or Neocerambyx gigas ( Zhang et al., 2020 ) were imitated to design such specific photonic films. These ideas enriched the design schemes of thermal photonics.…”

A nanograting-based flexible and stretchable waveguide for tactile sensing

“…Conventional rigid optical waveguides cannot match the requirements of flexible electronics and soft robotics [5][6][7]. Flexible and stretchable devices will be an important part for robotic tactile sensing system, which can realize the perception of human-machine interaction, and has a high degree of flexibility, stretchability, adaptability, sensitivity, biocompatibility, and immune to electromagnetic interference [8][9][10][11][12]. Wang et al fabricated a bioinspired flexible pressure sensors based on Ti3C2/MC biocomposite film with a pressure sensitivity of 24.63 kPa −1 , and silk Fibroin-MXene film also had been used as pressure sensor with biocompatibility and high-performance [13,14].…”

“…To achieve flexibility and stretchability of optical waveguide devices based on nanograting structures, new soft materials with optical transparency are needed as the cornerstones. Nowadays, new materials used to make flexible and stretchable photon sensing devices have been continuously developed [11,20]. They have several common characteristics, including transparency, flexibility, and stretchability.…”

A Nanograting Based Flexible and Stretchable Waveguide for Tactile Sensing

“…Nowadays, new materials used to make exible and stretchable photon sensing devices have been continuously developed. [17][18] They have several common characteristics, including transparency, exibility, and stretchability. These new optical soft materials can be divided into the following categories: elastomers, colloidal crystals, hydrogels and synthetic opals.…”

“…[5][6][7] Flexible and stretchable optical devices will be an important part for robotic tactile sensing system, which can realize the perception of human-machine interaction, and has a high degree of exibility, stretchability, adaptability, sensitivity, biocompatibility and immune to electromagnetic interference. [8][9][10][11][12] The exible and stretchable optical waveguide based on nanograting structure can be fabricated into tactile sensing devices with exibility and stretchability, and it has an extensive application in the eld in the area of wearable electronics and robotics. Li et al fabricated a exible waveguide device based on bendable chalcogenide glass, and a multi-neural-axis theory was used to optimize the strain distribution.…”