Physical Characterization of Immersion Method-Based Porous Paper Towards Sensing Application

Humidity sensors are essential to many applications, from climate control systems to healthcare. Paper-based humidity sensors have recently gained significant interest due to their simplicity, cost-effectiveness, and unique paper substrate properties. Paper is made of cellulose fibers that are woven together in a complex way to form a porous structure. These pores allow liquids to permeate the paper and stay inside the structure, which determines the absorption capacity. This study investigates the characterization of porous paper that has been formed through the immersion technique. The normal printing paper samples were immersed in different solutions, such as hydrochloric acid (HCl) and sodium hydroxide (NaOH), to yield porous paper. The effect of solution concentration on paper porosity and morphology has been observed. Based on the present findings, the use of HCl has demonstrated superior outcomes compared to NaOH in modifying paper porosity properties. The higher concentrations of HCl have been associated with enhanced porosity in the modified paper samples. The changes in porosity properties were achieved due to the removal of carbonate (CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>) filler from the paper cellulose structure. The highest percentage of porosity is 56.5%. These results offer important new understandings of optimizing chemical treatment techniques for customizing paper characteristics to fulfill certain application needs in humidity sensors.