With advances in electronics, the concept of flexible electronics has left traditional designs behind. Many concepts, such as sensors, transistors, soft robotics, data, and energy storage devices have begun to find more widespread and flexible areas of use. From this point of view, using environmentally friendly, abundant, and renewable natural materials that reduce carbon emissions in the production and disposal of these components is the first step toward the concept of sustainable flexible electronics. This review deals with the integration of sustainable natural materials obtained from plant, animal, and bacterial sources into sensors, displays, data storage, power generation, and soft robotic systems, with appropriate examples compiled from the last ten years. In addition, limitations in the use of sustainable materials as flexible electronic components and their potential for use in innovative electronic applications in the future are foreseen.

Back Cover: The illustration underlines the renewable raw materials that can be obtained from nature in the technological achievements Cem Bayram and co‐workers have gained in their laboratory studies, and showcase in article number 2100978. It is hoped that the delineation of the bridge between flexible electronics and sustainable biomass depicts the importance of this special issue.

This study presents the electrostatic repulsive features of electrochemically fabricated titanium dioxide nanotube (NT)-based membranes with different surface nanomorphologies in cross-flow biofiltration applications while maintaining a creatinine clearance above 90%. Although membranes exhibit antifouling behavior, their blood protein rejection can still be improved. Due to the electrostatically negative charge of the hexafluorotitanate moiety, the fabricated biocompatible, superhydrophilic, free-standing, and amorphous ceramic nanomembranes showed that about 20% of negatively charged 66 kDa blood albumin was rejected by the membrane with ∼100 nm pores. As the nanomorphology of the membrane was shifted from NTs to nanowires by varying fabrication parameters, pure water flux and bovine serum albumin (BSA) rejection performance were reduced, and the membrane did not lose its antifouling behavior. Herein, nanomembranes with different surface nanomorphologies were fabricated by a multi-step anodic oxidation process and characterized by scanning electron microscopy, atomic force microscopy, water contact angle analysis, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The membrane performance of samples was measured in 3D printed polyethylene terephthalate glycol flow cells replicating implantable artificial kidney models to determine their blood toxin removal and protein loss features. In collected urine mimicking samples, creatinine clearances and BSA rejections were measured by the spectrophotometric Jaffe method and high-performance liquid chromatography.