Hydrogels hold promise in agriculture as reservoirs of water in dry soil, potentially alleviating the burden of irrigation. However, confinement in soil can markedly reduce the ability of hydrogels to absorb water and swell, limiting their widespread adoption. Unfortunately, the underlying reason remains unknown. By directly visualizing the swelling of hydrogels confined in three-dimensional granular media, we demonstrate that the extent of hydrogel swelling is determined by the competition between the force exerted by the hydrogel due to osmotic swelling and the confining force transmitted by the surrounding grains. Furthermore, the medium can itself be restructured by hydrogel swelling, as set by the balance between the osmotic swelling force, the confining force, and intergrain friction. Together, our results provide quantitative principles to predict how hydrogels behave in confinement, potentially improving their use in agriculture as well as informing other applications such as oil recovery, construction, mechanobiology, and filtration.

Using experiments, we find that deformable particles can cooperatively squeeze through large-aspect ratio constrictions in porous media, even when isolated particles cannot.

Membrane fouling in desalination and wastewater treatment increases operating costs and energy consumption. Accordingly, research efforts have focused on developing new membrane materials and surface treatments that can resist fouling. Due to the case-specific nature of fouling, there is limited quantification of the impacts these novel anti-fouling membranes can have on water treatment systems. To address this gap, we report results of high-level analyses that evaluated savings in cost, energy consumption, and life-cycle greenhouse gas emissions when membranes with improved fouling resistance are used in brackish water desalination with reverse osmosis and wastewater treatment with anaerobic membrane bioreactors. To carry out these analyses, we used models Water-TAP 3 and GPS-X for desalination and wastewater treatment, respectively. We considered the influence of the membrane replacement rate and clean-in-place frequency in both scenarios. In the case of desalination, we also considered the influence of fouling factor and antiscalant dosage. In both scenarios, we determined that increasing membrane lifetime was the most influential factor in reducing operating expenses. Less influential factors included energy associated with increased pumping pressure to maintain a constant flux in the face of fouling and the frequency of clean-in-place events. Overall, desalination energy consumption was insensitive to the parameters we evaluated. Reducing energy associated with sparging in anaerobic membrane bioreactors offered the best opportunity to reduce AnMBR energy consumption in the wastewater treatment plant configuration we modeled. Greenhouse gas emissions were largely unaffected by the adoption of fouling-resistant membranes. Membranes made with new anti-fouling materials could be more expensive than current membranes. For the case studies we evaluate, depending on key variables such as membrane lifetime, the cost of desalination membranes could increase by 1.2−2.9 times, and the cost of anaerobic membrane bioreactor membranes could increase by up to 43% without operating costs increasing above our calculated baseline. This analysis highlights the promise of fouling-resistant membrane materials to reduce costs and energy consumption in water treatment systems. It also underscores a significant need for improved empirical data and multi-scale modeling to improve estimates of these savings.