Abstract: The multi-layered sand assembly comprising neat sand, super-hydrophilic and super-hydrophobic sands for feasible and sustainable desert agriculture is described. The ingredients such as PAM used in the super-hydrophilic sand layer and the PS-PMMA/DVB polymer for the super-hydrophobic layer are relatively less expensive and thus the overall development of the coated sand is economical and cost effective for the mass production of modified sand layers. The tandem action of high water absorption and retention over time by super-hydrophilic sand layer and high water repulsion to avoid water loss by super-hydrophobic sand of the proposed assembly would make the achievable agriculture in desert lands.

Abstract: A method for fabricating nanoporous polymer thin film includes steps as follows. A polymer thin film is provided, wherein a polymer solution including a polymer is coated on a substrate to form the polymer thin film. A swelling and annealing process is provided, wherein the polymer thin film is disposed inside a chamber with a vapor of a first solvent, the polymer thin film is swollen and annealed to form a swollen polymer thin film, and the swollen polymer thin film includes the polymer and the first solvent. A freezing process is provided, wherein the swollen polymer thin film is cooled to a temperature less than or equal to a crystallization temperature of the first solvent to crystallize the first solvent. A first solvent removing process is provided, wherein the first solvent is removed with a second solvent, such that a nanoporous polymer thin film is obtained.