For sustainability and environmental friendliness, the renewable biomaterials including cellulose have been widely used in flexible electronics, such as pressure sensors. Herein, the carbonized bacterial nanocellulose with excellent conductivity and wood-derived cellulose nanofibrils are combined to prepare the aerogel through directional ice-templating and freeze-drying. The obtained composite aerogel, which has a porous structure and aligned channels, is further employed as an active layer to prepare the resistive-type pressure sensor on a paper substrate. This pressure sensor exhibits remarkable flexibility, fast response, reliability, and especially adjustable sensitivity in a wide pressure range (0−100 kPa). In addition, the sensor's working mechanism and potential applications, such as motion detection, footstep recognition, and communication with smartphones via Bluetooth, are also well demonstrated. Moreover, this work provides novel insights into the development of green pressure sensors and the utilization of sustainable natural biomaterials in high-tech fields.

The economically viable synthesis of levulinic acid (LA), a promising and valuable renewable biomass-derived platform for bioproducts, with high carbon efficiency is a challenge. A direct and highly effective catalytic system for conversion of xylose residues (XRs) into LA under mild conditions by using FeCl 3 as catalyst and cheaply available NaCl as promoter has been developed. The NaCl solution exhibits high carbon efficiency in LA (68.0 mol %) when compared with the non-NaCl systems (48.5 mol %) due to the moderate increase of the acidity and the higher viscosity of the NaCl system than water. The experimental results demonstrated that the presence of NaCl caused no distinctive changes on reaction pathways but increased the dissolution rate and the hydrolysis rate of XRs cellulose. Moreover, further integration of our degradation process with a reactive extraction step makes energy-efficient separation of LA. The NaCl solutions easily and efficiently extracted LA into LA-derived solvent 2methyltetrahydrofuran from aqueous solutions. The efficiency and integration of the reaction process presented a great potential for LA production from renewable biomass with the aid of concentrated seawater.

Carbon aerogels possess low density, high conductivity, and excellent electrochemical properties, which have potential applications in sensor and energy storage. However, the fabrication methods of carbon aerogels are very complicated, and the applications are usually restricted by their low compressibility, fragile structure, and poor electrical property. Herein, we report a very facile approach for the preparation of compressible, fatigue resistant, conductive, and pressure-sensitive carbon aerogels by pyrolysis of cellulose nanofibers aerogel using melamine foams as the skeleton. The wet aerogels are dried directly in ambient pressure without any volume shrinkage, which is remarkably contrasted to the complex and time-consuming drying process of traditional aerogels. The resulting carbon aerogels exhibit excellent performance, including a low density of 11.23 mg cm–3, high electrical conductivity of 0.378 S cm–1, high sensitivity of 1.841 kPa–1, and outstanding mechanical properties. The assembled carbon aerogel sensors can monitor human activities and pulse vibration, demonstrating the great potential application in wearable devices. Moreover, the high nitrogen content and hydrophilic property enable the carbon aerogels to be used as compressible electrodes with a specific and areal capacitance of 92.2 F g–1 and 461 mF cm–2, respectively, showing the promising prospect in flexible supercapacitors.

Recently, sustainable triboelectric nanogenerators (TENGs) based on biodegradable biomaterials have attracted tremendous attention to efficiently harvest mechanical energy in a cost-effective and environment-friendly strategy. Lignin, as the second most abundant...

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