Biodegradable and biocompatible elastic materials for soft robotics, tissue engineering or stretchable electronics with good mechanical properties, tunability, modifiability, or healing properties drive technological advance, yet they are not durable under ambient conditions nor combine all attributes in a single platform. We have developed a versatile gelatin-based biogel, which is highly resilient with outstanding elastic characteristics yet degrades fully when disposed. It self-adheres, is rapidly healable and derived entirely from natural and food-safe constituents. We merge for the first time all favorable attributes in one material that is easy to reproduce, scalable and low-cost in production under ambient conditions. This biogel is a step towards durable, lifelike soft robotic and electronic systems that are sustainable and closely mimic their natural antetypes. Main: In 2025, an estimated 6 million tons of garbage will be generated per day 1 , with tech disposables being a rapidly growing contributor. End-of-lifetime appliances contain valuable materials that are laborious in recovery or toxic substances that are readily released into nature through landfilling or improper treatment 2. Biodegradable 3-6 and transient systems 7 are promising routes towards closing the loop on waste generation and create new opportunities for secure systems, but often at the cost of compromises in performance. Complex biological systems bridge this gap. They unite seemingly antagonistic properties-tough yet adaptive, durable and self-healing yet degradable-allowing them to perform a myriad of intricate tasks. Embodiments of technologies that intimately interface with humans naturally benefit from mimicking such soft, functional forms. A range of biomimetic systems 8 including soft machines 9 and electronic skins 10 achieve a high level of functionality by introducing self-healing 11,12 , intrinsic stretchability 13 , or the insightful merging of soft-to-hard materials 14. Waste flow issues and in vivo applications that avoid multiple surgeries are tackled with inextensible devices in the form of edible 3,15 and transient electronics 7,16. However, introducing stretchability to degradable devices remains challenging. Recent approaches focusing on stretchable biodegradable sensors 5 require expensive materials and are still wired to bulky measurement systems hindering implementation as wearable devices. Challenges here stem from the diverse material requirements,

Soft robotics greatly benefits from nature as a source of inspiration, introducing innate means of safe interaction between robotic appliances and living organisms. In contrast, the materials involved are often nonbiodegradable or stem from nonrenewable resources, contributing to an ever-growing environmental footprint. Furthermore, conventional manufacturing methods, such as mold casting, are not suitable for replicating or imitating the complexity of nature’s creations. Consequently, the inclusion of sustainability concepts alongside the development of new fabrication procedures is required. We report a customized 3D-printing process based on fused deposition modeling, printing a fully biodegradable gelatin-based hydrogel (biogel) ink into dimensionally stable, complex objects. This process enables fast and cost-effective prototyping of resilient, soft robotic applications from gels that stretch to six times their original length, as well as an accessible recycling procedure with zero waste. We present printed pneumatic actuators performing omnidirectional movement at fast response times (less than a second), featuring integrated 3D-printed stretchable waveguides, capable of both proprio- and exteroception. These soft devices are endowed with dynamic real-time control capable of automated search-and-wipe routines to detect and remove obstacles. They can be reprinted several times or disposed of hazard-free at the end of their lifetime, potentially unlocking a sustainable future for soft robotics.

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Incorporating large organic cations to form 2D and mixed 2D/3D structures significantly increases the stability of perovskite solar cells. However, due to their low electron mobility, aligning the organic sheets to ensure unimpeded charge transport is critical to rival the high performances of pure 3D systems. While additives such as methylammonium chloride (MACl) can enable this preferential orientation, so far, no complete description exists explaining how they influence the nucleation process to grow highly aligned crystals. Here, by investigating the initial stages of the crystallization, as well as partially and fully formed perovskites grown using MACl, the origins underlying this favorable alignment are inferred. This mechanism is studied by employing 3‐fluorobenzylammonium in quasi‐2D perovskite solar cells. Upon assisting the crystallization with MACl, films with a degree of preferential orientation of 94%, capable of withstanding moisture levels of 97% relative humidity for 10 h without significant changes in the crystal structure are achieved. Finally, by combining macroscopic, microscopic, and spectroscopic studies, the nucleation process leading to highly oriented perovskite films is elucidated. Understanding this mechanism will aid in the rational design of future additives to achieve more defect tolerant and stable perovskite optoelectronics.

Perovskite Solar Cells In article 2208061, Lukas E. Lehner, Martin Kaltenbrunner, and co‐workers report the controlled nucleation of quasi‐2D perovskites at the liquid–air interface of the precursor solution. Restricting the initial crystal growth to the surface of the liquid results in highly aligned perovskite thin films with improved charge transport, enabling efficient solar cells with excellent stability.