Ingenuity of Materials and Designs in Soft Robotics

The ongoing COVID-19 pandemic challenges our global society in every aspect, and demands all to work together in finding solutions. The scientific community is at the forefront of these efforts, accelerating technological advances such as the deployment of robots, which are poised to tackle many of the challenges of humankind. Driven by the desire of life-like agility and dexterous functionalities, soft forms of robots are naturally emerging with their extraordinary capabilities endowed by ingenuity in materials, designs, system integration, and computational domains. The evolution of soft robotics is, in many aspects, inspired by nature or biology, with the quest for (better-than-) human capabilities, safe operation, and close collaboration with users. In this Special Issue, we present research perspectives to address a wide variety of pivotal topics that shape the future development of soft robotics. Soft robotics shifted the paradigm of traditional robotics, from construction, interaction with the environment, locomotion or transduction modalities, and even potentially cradle-to-cradle sustainability prospectus. In the pursuit of safe and user-friendly human–robot interactions, dynamic and stimuli-responsive fibers and fabrics that deliver sensing and actuating abilities for soft robotics with salient interactive features are discussed by Pooi See Lee and co-worker in article number 2002640. Designing robots capable of self-editing or self-morphing, emulating living organisms, in order to be more effective in executing tasks in a changing environment can be addressable with innovations in multifunctional materials with somatic control, as discussed by Rebecca Kramer-Bottiglio and co-workers in article number 2002882. While soft robots are constructed to operate in a mechanically unobstructed manner, even imperceptible embodiments with optically transparent hardware or components are envisioned and will extend the field of applications. Fabrication of transparent soft actuators, sensors, or imperceptible camouflage robotic skins are highlighted by Seung Hwan Ko and co-workers in article number 2002397. Endowing artificial skin perception for soft robotics will enhance the flexible computing with low-latency and efficient information processing as pointed out by Xiaodong Chen and co-workers in article number 2003014. Meanwhile, self-repairing abilities through the use of intelligent soft materials for damage tolerance are poignantly delineated in article number 2002800 by Benjamin Chee Keong Tee and co-workers. The progress of soft robotics has called for biomimetic approaches to realize unique materials properties in meeting desirable functions. In addition, bioinspired strategies are extensively considered in the development of sensing, actuation, and control, as introduced by Hamid Marvi and co-workers in article number 2003139. Through the emulation of physical flexibility and versatility of animals to the inspiration drawn from caterpillars, snakes, and worms, a cornucopia of unique opportunities has been created for soft robotics to contribute to exciting applications, for example in the field of biomedical devices. Incorporation of smart materials and additive manufacturing technologies such as 3D printing has provided unique building blocks to enable augmented capabilities of soft robotics including grasping and releasing or sophisticated manipulation of objects, as introduced by Shlomo Magdassi and co-workers in article number 2003387. In particular biomedical applications will benefit from recent developments merging flexible electronics and soft robotics, as outlined by Takao Someya and co-workers in article number 2004416. Design considerations and materials properties could enhance exteroceptive and interoceptive capabilities. The recent progress in artificial muscles for interactive soft robotics charted by the development of stimuli responsive hybrid materials and their mechanism of soft actuation is described by Jiangxin Wang and co-workers in article number 2003088, and the state-of-the art in uniting the best of two soft actuator technologies—electroactive and hydraulic—for stronger and faster artificial muscles is outlined by Christoph Keplinger and co-workers in article number 2003375. Emerging organic materials for actuators and their digital printing technologies in the fabrication of haptic actuators are drawing interest in the potential to incorporate tactile surfaces and kinesthetic substrates, as highlighted by Tse Nga Ng and co-workers in article number 2002541. Furthermore, the key features of versatile and multi-locomotive functionalities in soft robotics that have endowed the possibility of untethered navigation through unpredictable and complex terrains are discussed by Guo Zhan Lum and co-workers in article number 2003558. Meanwhile, Woo Soo Kim and co-workers highlight the opportunities opened up by incorporating 3D structural sensors in article number 2002534. Alternative strategies for control, sensing, and actuation in soft robotics that are inspired by nature include harnessing mechanical instabilities and metamaterials as described by Ramses Martinez and co-workers in article number 2006939. To prolong a wide range of on-board functions, energy harvesting and storage, which can be realized using soft and stretchable materials are reviewed by Michael Dickey and co-workers in article number 2004832. As we progress toward innovative concepts and capture capabilities of soft robotics, concerns on sustainability are becoming the next challenging frontier of soft robotics, as described by Martin Kaltenbrunner and co-workers in article number 2004413. In summary, this special issue highlights the pivotal roles played by materials innovations and the integration of systems coupled with predictive simulations. They will continue to be crucial in steering the field of soft robotics to greater heights, making headway with transformative deployment into the marketplace, various industrial segments, and our society as a whole. Finally, we are indebted to all the authors who have contributed to this special issue during this unprecedented challenging pandemic period. We are most grateful for the invaluable support and professional editing from the whole editorial team of Advanced Materials, in particular Dr. Jolke Perelaer and James Cook. Pooi See Lee received her Ph.D. from National University of Singapore in 2002. She joined the School of Materials Science and Engineering, Nanyang Technological University as an Assistant Professor in 2004. She was promoted to tenured Associate Professor in 2009 and full Professor in 2015. Her research focuses on nanomaterials for energy and electronics, flexible and stretchable devices, and functional materials for soft robotics. Martin Kaltenbrunner is a full professor at the Johannes Kepler University Linz, heading the Soft Matter Physics Division and the LIT Soft Materials Lab. He received his master's and Ph.D. degrees in physics from the Johannes Kepler University in 2008 and 2012, respectively. He then joined the Someya–Sekitani Lab for Organic Electronics at The University of Tokyo as postdoctoral researcher prior to his present position. His research interests include soft electronics and machines, biodegradable soft materials, photovoltaics, lightning and thin-film transistors, soft transducers and robotics, flexible and stretchable electronics, and electronic skins.