Solar cell substrates require high optical transparency but also prefer high optical haze to increase the light scattering and consequently the absorption in the active materials. Unfortunately, there is a trade-off between these optical properties, which is exemplified by common transparent paper substrates exhibiting a transparency of about 90% yet a low optical haze (<20%). In this work, we introduce a novel transparent paper made of wood fibers that displays both ultrahigh optical transparency (∼ 96%) and ultrahigh haze (∼ 60%), thus delivering an optimal substrate design for solar cell devices. Compared to previously demonstrated nanopaper composed of wood-based cellulose nanofibers, our novel transparent paper has better dual performance in transmittance and haze but also is fabricated at a much lower cost. This high-performance, low-cost transparent paper is a potentially revolutionary material that may influence a new generation of environmentally friendly printed electronics.

Conductive hydrogels are promising interface materials utilized in bioelectronics for human-machine interactions. However, the low-temperature induced freezing problem and water evaporation-induced structural failures have significantly hindered their practical applications. To address these problems, herein, an elaborately designed nanocomposite organohydrogel is fabricated by introducing highly conductive MXene nanosheets into a tannic acid-decorated cellulose nanofibrils/polyacrylamide hybrid gel network infiltrated with glycerol (Gly)/water binary solvent. Owing to the introduction of Gly, the as-prepared organohydrogel demonstrates an outstanding flexibility and electrical conductivity under a wide temperature spectrum (from −36 to 60 °C), and exhibits long-term stability in an open environment (>7 days). Additionally, the dynamic catechol-borate ester bonds, along with the readily formed hydrogen bonds between the water and Gly molecules, further endow the organohydrogel with excellent stretchability (≈1500% strain), high tissue adhesiveness, and self-healing properties. The favorable environmental stability and broad working strain range (≈500% strain); together with high sensitivity (gauge factor of 8.21) make this organohydrogel a promising candidate for both large and subtle motion monitoring.

Flexible and highly sensitive humidity sensors are crucial for humidity detection. In this study, a flexible cellulose nanofiber/carbon nanotube (NFC/CNT) humidity sensor with high sensitivity performance was developed via fast vacuum filtration. CNTs were well dispersed in water by using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized NFC as a dispersant. More importantly, NFC also acted as a humidity sensitive material, achieving superior performance of NFC/CNT humidity sensors. The obtained NFC/CNT humidity sensor with 5 wt % CNT loading exhibits outstanding sensitive performance, and its response value reaches a maximum of 69.9% (ΔI/I 0) at 95% relative humidity (RH). It also displays good bending resistance and long-term stability. In addition, the NFC/CNT humidity sensor was employed to monitor human breath. Therefore, we believe that the flexible, highly sensitive, and simply designed NFC/CNT humidity sensor is a promising candidate for various applications in the field of humidity measurement.

[1] We studied in situ colloid mobilization under transient flow conditions using columns repacked with Hanford sediments. Rainfall infiltration was experimentally simulated using different flow rates and initial moisture conditions. Five series of column experiments were performed with initial infiltration rates of 0.018, 0.036, 0.072, 0.144, and 0.288 cm/min, and the columns reached water saturations in the range of 53 to 81%. The infiltration of water into the columns provided unfavorable conditions for colloid attachment to the sediments. Colloids were eluted by the infiltrating water with the peak colloid concentrations in the outflow coinciding with the arrival of the infiltration front. A larger flow rate led to a greater amount of colloids released from the column. The cumulative amount of colloids released was proportional to the column water content established after steady state flow rates were achieved. We used the advection-dispersion equation with a first-order colloid release reaction to analyze the experimental data. The colloid release rate coefficient increased with the increase of water content. We calculated forces exerted on colloids, and found that electrostatic and van der Waals interactions, calculated based on the DLVO (Derjaguin-Landau-Verwey-Overbeek) theory, and hydrodynamic forces, were all less important than capillary forces in controlling colloid release. In one experiment, the ionic strength of the infiltration solution was increased, such that colloid attachment was favorable. Nonetheless, colloids were mobilized and eluted with the infiltration front, implying that non-DLVO forces, such as capillary forces, played a prominent role in colloid mobilization.Citation: Shang, J., M. Flury, G. Chen, and J. Zhuang (2008), Impact of flow rate, water content, and capillary forces on in situ colloid mobilization during infiltration in unsaturated sediments, Water Resour. Res., 44, W06411,

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