text: Many PDRC thin films have been developed which have demonstrated very high solar reflectance and heat emittance. However, films with precise patterns or structures are not scalable "due to the cost and technical difficulties inherent in large-scale precise lithography," as per Khan et al., or "due to complex nanoscale lithography/synthesis and rigidity," as per Zhou et al.
  The polyacrylate hydrogel film from the later study has broader applications, including potential uses in building construction and large-scale thermal management systems. This research focuses on a polyacrylate film developed for hybrid passive cooling. The film uses sodium polyacrylate, a low-cost industrial material, to achieve high solar reflectance and high mid-infrared emittance. A significant aspect of this material is its ability to absorb atmospheric moisture, enabling it to provide both radiative and evaporative cooling. This dual mechanism allows for efficient cooling even under varying atmospheric conditions, including high humidity or limited access to clear skies.
  Some researchers have attempted to overcome this with various methods:
  * Zhang et al. (2020), facile microstamping method film on low-cost polymer PDMS, solar reflectance 95%, heat emittance 96%, daytime temperature reduction up to 5.1 °C, "promising for scale-up production."
  * Zhang et al. (2021), low-cost film developed with a phase inversion process using cellulose acetate and calcium silicate, solar reflectance 97.3%, heat emittance 97.2%, daytime temperature reduction up to 7.3 °C below ambient (average net cooling power of 90.7 W m), "a low-cost, scalable composite film with novel dendritic cell like structures," tested in Qingdao.
  * Fan et al. (2022), eco-friendly preparation of superhydrophobic porous polydimethylsiloxane (PDMS) radiative cooling film, daytime temperature reduction up to 11.52 °C below ambient, "the film is promising to be widely used for long-term cooling for outdoor applications."
  * Nie et al. (2022), composite film made of fluorine-free reagents and  particles, solar reflectance 85%, heat emittance 95%, daytime temperature reduction average 12.2 °C, manufactured with "a simple preparation process, which has characteristics of low-cost environmental friendliness and excellent machinal durability," tested in Hubei.
  * Zhong et al. (2023), hierarchical flexible fibrous cellulose (wood pulp) film, solar reflectance 93.8%, heat emittance 98.3%, daytime temperature reduction up to 11.3 °C below ambient, study is "the first time to realize high crystallinity and hierarchical microstructures in regenerated cellulose materials by the self-assembly of cellulose macromolecules at the molecular level," which "will provide new perspectives for the development of flexible cellulose materials."