A strategy for bonding water-rich hydrogels to diverse materials for electronic skins, energy storage, and soft optics is reported.

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,

End-of-lifetime appliances such as consumer electronics are typically trashed, as the various product designs and material compositions are difficult to recycle yet are cheaply produced. Additionally, the unsustainable use of rare and often toxic materials poses an environmental threat when released into nature due to improper treatment or landfilling. [2] Easy to recycle device designs, low-cost and renewable materials, and biodegradable or transient systems are promising approaches toward technologies with a closed life cycle and establish new opportunities across different fields from medicine and environmental monitoring to security and intelligence applications. [3] Current developments in robotics that focus on safe human-machine interaction, swarm robotics, and untethered autonomous operation are often inspired by nature's diversity. [4] The complexity we find in nature drives scientists from various fields to establish soft and lightweight forms of robots that aim to replicate or mimic the fluent motion of animals or their efficient energy management. [5,6] In future, the increased integration of such soft robots in our everyday life raises, in close analogy to consumer electronics, environmental concerns at the end of their life cycle. Again, we can learn here from nature and design our creations sustainably and mitigate the problems of currently used technology. In contrast to standardized industrial robots that are already integrated in recycling loops, bioinspired robotics will find various applications in diverse ecological niches. [7] Possible examples range from soft healthcare machines that support elderly people in their everyday lives to robots that first harvest produce and afterwards become compost for next season's plants. Current demonstrations with transient behavior include elastic pneumatic actuators, [8] wound patching millibots operating in vivo, [9] robot swarms for drug delivery, [10] or small grippers that are controlled by engineered muscle tissues. [11] These developments benefit from major research activities toward bioresorbable electronic devices, [12] which are mainly explored for the biomedical sector, and sustainable energy storage technology, [13] seeking to resolve environmental concerns for the increasing demand of energy for mobile appliances. Bringing those fields together will be the future challenge for autonomous robots, whether their development focuses on performance, sustainability, or both. The efficient integration of actuators, sensors, computation, and energy into a single robot will require new concepts and ecofriendly solutions, and can only be successful if material scientists, chemists, engineers, biologists, computer scientists, and roboticists alike join forces.The advancement of technology has a profound and far-reaching impact on the society, now penetrating all areas of life. From cradle to grave, one is supported by and depends on a wide range of electronic and robotic appliances, with an ever more intimate integration of the digital and biological sp...

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.

High-speed locomotion is an essential survival strategy for animals, allowing populating harsh and unpredictable environments. Bio-inspired soft robots equally benefit from versatile and ultrafast motion but require appropriate driving mechanisms and device designs. Here, we present a class of small-scale soft electromagnetic robots made of curved elastomeric bilayers, driven by Lorentz forces acting on embedded printed liquid metal channels carrying alternating currents with driving voltages of several volts in a static magnetic field. Their dynamic resonant performance is investigated experimentally and theoretically. These robust and versatile robots can walk, run, swim, jump, steer and transport cargo. Their tethered versions reach ultra-high running speeds of 70 BL/s (body lengths per second) on 3D-corrugated substrates and 35 BL/s on arbitrary planar substrates while their maximum swimming speed is 4.8 BL/s in water. Moreover, prototype untethered versions run and swim at a maximum speed of 2.1 BL/s and 1.8 BL/s, respectively.

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large areas available on the skin or within the body. [3] Intrinsically stretchable batteries effectively make use of available space while perfectly complying to deformations and maintaining comfort for the wearer. [4][5][6] Recent developments exploit high-energydensity materials, such as Zn and Li-ion based batteries, [7][8][9][10] to enhance battery capacity and close the gap to rigid-island designs. [11] Despite the progress in capacity and rechargeability, the principle design of planar intrinsically stretchable batteries has largely remained unchanged. The interplay of electrodes, efficient current collectors, highly ionically conductive separators/gelelectrolytes, and their conformal orientation must collectively be optimized to boost battery performance. Promising solutions for single components, including multilayer current collectors, [12] tough electrodes, [13] and self-healing gel-electrolytes [14] were demonstrated recently. However, many prototypes still use the coplanar orientation of electrodes [4,12,[15][16][17] as proposed for the first soft batteries. [18] This design sacrifices performance due to increased ionic pathways in the gel electrolytes. Introducing a sandwich design of stacked battery components (Figure 1a), greatly reduces ionic pathways and therefore the internal resistance of the battery. [19] Soft (sandwich-design) batteries require electron-insulating separators, which have to meet high ion conductivity, extensibility, and chemical inertness. Hydrogels are often used in water-based systems, serving as gel Powering soft embodiments of robots, machines and electronics is a key issue that impacts emerging human friendly forms of technologies. Batteries as energy source enable their untethered operation at high power density but must be rendered elastic to fully comply with (soft) robots and human beings. Current intrinsically stretchable batteries typically show decreased performance when deformed due to design limitations, mainly imposed by the separator material. High quality stretchable separators such as gel electrolytes represent a key component of soft batteries that affects power, internal resistance, and capacity independently of battery chemistry. Here, polymerized high internal phase emulsions (polyHIPEs) are introduced as highly ionically conductive separators in stretchable (rechargeable) batteries. Highly porous (>80%) separators result in electrolyte to polyHIPE conductivity ratios of below 2, while maintaining stretchability of ≈50% strain. The high stretchability, tunable porosity, and fast ion transport enable stretchable batteries with internal resistance below 3 Ω and 16.8 mAh cm −2 capacity that power on-skin processing and communication electronics. The battery/separator architecture is universally applicable to boost battery performance and represents a step towards autonomous operation of conformable electronic skins for healthcare, robotics, and consumers.

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