The present invention provides an effortless, economical method for increasing the hydrophobicity of the paper or paper like material. In an aspect, the invention provides a non-toxic, biodegradable cellulose reactive sizing agent that when printed on the paper or paper like material followed by heating the paper or paper like material increases the hydrophobicity of the paper; wherein the cellulose reactive sizing agent comprises a vegetable oil suspended in a carrier solvent. In yet another aspect, the invention provides a device for printing cellulose reactive sizing agent on the paper or paper like material. The invention also provides a paper fluidic device and a method for manufacturing the same.