All-Cellulose Superabsorbent Heterostructures Comprising Fiber Aerogels and Nanofibril Sheets

Superabsorbent polymers (SAPs) are essential components in absorption products for food packaging, agriculture, wound dressings, and hygiene. Modern absorption products are designed to rapidly absorb and transport liquids to SAPs, which drains the porous networks and hold liquids under pressure as hydrogels. However, the carbon footprint of these massively used, fossil-based products is high, leading to an urgent need to develop biobased superabsorbents. Although commercial SAPs have an absorption capacity under load that is challenging to surmount, their powder form complicates processing. Thus, biobased alternatives can compete with other advantages, such as intelligently designed self-supporting structures preferably manufactured in sustainable roll-to-roll processes. As a pioneering step, this study presents all-cellulose superabsorbent heterostructures prepared by combining macroporous fiber-based aerogels with highly swelling cellulose nanofibril (CNF) sheets. The aerogel rapidly absorbs 30 g g–1 of liquid, which is rapidly transferred to the CNF sheets with a maximum capacity of 246 g g–1, holding liquids at pressures of up to 0.9 MPa. The heterostructure is also equipped with a simple, sustainable conductometric water-uptake sensor to follow the liquid uptake and saturation level. Using unmodified raw materials from the forest industry in a scalable process with the potential for roll-to-roll manufacturing makes these all-cellulose heterostructures a competitive alternative to commercial SAPs in a carbon-neutral society.