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Here, we highlight 35 global researchers approximately under the age of 35. This third annual cohort was self-generated by initial seed invitations sent by the editorial team, with each contributor suggesting two more in a nominally supervised self-selecting pyramid-like scheme. The final collection reflects both the diversity and excitement across the field of materials science.

In biological or abiotic systems, rhythms occur, owing to the coupling between positive and negative feedback loops in a reaction network. Using the Semenov–Whitesides oscillatory network for thioester hydrolysis as a prototype, we experimentally and theoretically analyzed the role of fast and slow inhibitors in oscillatory reaction networks. In the presence of positive feedback, a single fast inhibitor generates a time delay, resulting in two saddle-node bifurcations and bistability in a continuously stirred tank reactor. A slow inhibitor produces a node-focus bifurcation, resulting in damped oscillations. With both fast and slow inhibitors present, the node-focus bifurcation repeatedly modulates the saddle-node bifurcations, producing stable periodic oscillations. These fast and slow inhibitions result in a pair of time delays between steeply ascending and descending dynamics, which originate from the positive and negative feedbacks, respectively. This pattern can be identified in many chemical relaxation oscillators and oscillatory models, e.g., the bromate–sulfite pH oscillatory system, the Belousov–Zhabotinsky reaction, the trypsin oscillatory system, and the Boissonade–De Kepper model. This study provides a novel understanding of chemical and biochemical rhythms and suggests an approach to designing such behavior.

Nonlinear chemical reactions produce interesting chemohydrodynamic patterns in an unstirred medium, which act as interesting demonstrations to display the novel phenomena in a nonequilibrium chemical system. Here, we report new outreach experiments: pH chemohydrodynamic patterns modulated by sodium polyacrylate in the bromate–sulfite–ferrocyanide (BSF) reaction system. In an unstirred Petri dish, transient pH stripe patterns for a bromate–sulfite–ferrocyanide reaction system driven by proton autocatalysis and isothermal density-induced flow can be initiated in the center of approximately two-dimensional Petri dishes by adding a small amount of sulfuric acid solution with a certain concentration. Finally, the transient patterns are restored to the homogeneous high pH state due to proton negative feedback. The addition of sodium polyacrylate can not only lead to horizontal Marangoni flow for forming filamentary pH patterns but also decreases the diffusion of hydrogen ions, which results in a monotonic relationship between the pattern lifetime and polyacrylate concentration. Through these simple, lively and interesting experimental demonstrations, undergraduate students majoring in chemistry can realize the effect of transportations such as diffusion, density-induced flow, and Marangoni flow on complex pattern formation driven by a simple inorganic clock reaction.

Phase transition between liquid and solid is a ubiquitous phenomenon in nature and has been used widely in scientific and industrial communities. Most metals have high melting points, posing a challenge to studying and using their phase transition-enabled abrupt changes in properties. Gallium and its alloys with low melting points (termed as liquid metal) can easily switch between solid and liquid in response to thermal energy at room temperature, accompanied by a significant variation in properties, including thermal enthalpy, stiffness, shape and volume, surface adhesion force, and catalytic activity, providing a rather straightforward and effective platform to observe the phase transition phenomena of metals and leverage switchable properties. The overwhelming majority of these studies and applications have quickly emerged in the last 10 years, which is at the beginning of the journey of applying the phase transition of liquid metal. This article is dedicated to presenting a systematic review of the fundamentals and latest progress of phase transition science and engineering of liquid metal and proposing future research directions and the main challenges that lie ahead. It is expected to help mold the category of such cutting-edge subjects and inspire more research and applications in the near future.

Metallic shape transformable materials hold big promise for improved intracellular therapy. However, until now, there have been rather limited biomedical practices for such materials, which is mainly attributed to their inherent uncontrolled morphological transformation, non-selective destruction, and difficult metabolization. Here, Ga-based liquid metal is found to exhibit remarkable transformation from sphere shape to cactus-like structure in micro-scale under freezing. Particularly, only cell membrane-encapsulated Ga particles (Ga/MPs) display dramatic shape variation in cooling under cryo-transmission electron microscopy (cryo-TEM). Following that, cryo-triggered Ga/MPs transformers are designed for effective endosomal escape via a physical mechanical strategy to disrupt the endosomal membrane, which leads to highly efficient cancer cell killing. Ga/MPs exhibit significant tumor growth inhibition and prolonged survival time according to the collaborative efficacy of cryoablation and endosomal escape mechanism, as well as high-resolution in vivocomputed tomography (CT) imaging. This study opens a versatile strategy based on Ga particle transformer to assist high-performance precise intracellular therapy in future tumor therapeutics.

Graphical Abstract: TOC: Schematic illustration of liquid metal fibers and their fabrication technologies: 3D printing, coating of liquid metal on fibers, injection of liquid metal into hollow fibers, spinning of LM composites. Liquid metal fibers can be applied as stretchable electronics, smart clothing, health monitoring, electrical switches, and shape memory devices.

Shape transformable materials that can respond to external environments have attracted widespread interest over the fields of soft robotics, flexible electronics, and tissue engineering. Among stimuli-responsive materials, liquid metals exhibit rather unique characteristics of versatile morphological changes upon diverse stimuli, including chemicals, electrical field, and mechanical force, etc. Herein, a superfast (few milliseconds), large-scaled (13.8% deformation increase), and fierce (cracks formation) transformation of liquid metal microdroplets (LMMs) with strong impulse expanded force due to liquid–solid phase transition in a dual fluid system composed of LMMs and aqueous solution is reported. When subject to low-temperature stimulus, LMM would transform from ellipsoidal shape to amorphous shape induced by thermal stress, driving the shape morphing. Furthermore, the phase changes of LMMs as well as the formation of surrounding ice crystals are proven to be responsible for this phenomenal behavior. The densification of ice crystals is demonstrated to play a significant role in the transformable behavior. In particular, these nonconductive LMMs in aqueous solutions are discovered to turn into conducive materials with an impedance change of about 105times. The present discovery is of fundamental and practical significance, and would open new venues in fields such as fluid mechanics, thermal science, flexible electronics, biomedicine, and so forth.

Wearable electronics incorporating electronic components into commonly used fabrics can serve as new-generation personalized health-care systems for applications ranging from health-care monitoring to disease treatment. Conventional rigid materials including gold, silver, and copper generally require a complicated fabrication process to be sewn into clothes. At the same time, other high-stretchable nonmetal materials such as conductive polymers generally have a limitation of low electroconductivity, restricting their further applications. Recently, gallium-based liquid metals have exhibited superior advantages in flexible electronics and have presented valuable potential in creative printing technologies. Here, we proposed a novel wearable electronics prepared through roller printing technology based on the adhesion difference of semiliquid metal (Cu-EGaIn, eutectic gallium-indium mixed with copper microparticles) on cotton fabrics and polyvinyl acetate (PVAC) glue. Results have shown that the surface topography and chemical interaction of fabrics and PVAC glue determine the adhesion effect with the Cu-EGaIn mixture. The electric experiments have demonstrated the electromechanical stability of the fabricated lines on fabrics. Further, a series of smart fabrics were developed including an interactive circuit, stretchable light-emitting diode array, and thermal management device with advantages of easy operation, low cost, and large-area fabrication to show practical applications in the method. This strategy may play an important role in the design and fabrication of smart fabrics, contributing to the development of customized health-care systems.

Injecting CO2into shale gas reservoirs to improve shale gas recovery is a promising technique, with the dual benefit of CO2sequestration. To reveal the coupling effects caused by adsorption–desorption properties on shale gas exploitation and the physical properties of the reservoir, a fluid–solid coupling model of fluid seepage and deformation of the shale is constructed. First, the model was validated, and then, it was used to study the effect of injection of CO2on shale gas exploitation and reservoir physical properties changes. The results demonstrate that CO2injection improves shale gas recovery mainly through its higher competitive adsorption capacity, replacing CH4, increasing CH4partial pressure, enhancing CH4diffusion, and the flooding effect on CH4. Increasing the CO2injection pressure has a positive effect on CH4production and CO2sequestration, but CO2transport is accelerated, and breakthrough occurs early. Lower production pressure is beneficial to CH4production but detrimental to CO2sequestration, so it is necessary to determine the injection and production pressure by combining CO2flooding in CH4and CO2sequestration. In addition, the coupled effect of effective stress change and gas adsorption/desorption-induced matrix expansion/contraction controls the evolution of reservoir permeability. However, the influencing factors that play a dominant role in different locations of the reservoir change with the exploitation period, so the change law of permeability is more complex. This study is of great theoretical and practical significance for elaborating and summarizing the relationship between adsorption–desorption, stress–strain, and gas transport in shale, predicting the effects of enhanced shale gas recovery and CO2sequestration.

In the present study, a magnetic liquid metal droplet (MLMD), which can be stretched in large scales both horizontally and vertically in the free space, is introduced. This MLMD is fabricated based on a multimaterial system including liquid metals, iron particles, and electrolytes. Such remarkable stretching capacity is reversible, long-lasting, and can be repeated for multiple times. The seemingly contrary properties, the good stretchability and the mechanic strength for three-dimensional (3D) stretch, should owe to the surface oxide over the MLMD. On the basis of the 3D stretching ability of the MLMD, an intelligent scalable conductor was achieved, which can make electrical connections at various directions in the 3D free space. Moreover, the vertically stretched MLMD can move horizontally with its half body in the solution and the other half in the air, which resembles the nature of an upright walking amphibian. All the behaviors can be precisely, conveniently, and contactlessly controlled by the magnetic field provided by permanent magnets. With all the appealing properties, this MLMD presents a fundamental and promising platform for the liquid metals to further develop the multi-freedom actuation in free space and eventually lead to the dynamically reconfigurable intelligent and biomimetic soft robots in the future.

Flexible Skin Patches In article 2202872by Xuyang Sun, Hongzhang Wang, Jing Liu and co‐workers, a flexible skin patch with improved adhesiveness to skin is designed for conformable and non‐invasive tumor therapy. This multifunctional technology can achieve severe destruction on tumor via an “ice and fire” mechanism, mediated by cryoablation, magnetic hyperthermia, as well as immune response activation.

Innovations on materials and technologies have greatly promoted the rapid development of wearable electronics from disease diagnosis to therapeutics. For superficial skin tumors, skin‐attachable patches possess the advantages of minimally invasive property, alleviative side effects, and high efficiency. The development of noninvasive techniques and devices is still in urgent demands. Here, a flexible skin patch fabricated through a facile preparation method is reported for noninvasive hybrid thermophysical therapy and adaptative immune function enhancement. The liquid metal enabled skin patch is demonstrated with high conductivity, certain stability, biocompatibility, and an enhanced adhesive merit on skin surfaces for cryoablation therapy and magnetic hyperthermia therapy. The skin patch exhibits remarkably conformable heating and cooling performance toward the treatment of 4T1 breast tumors. The magnetic resonance images also indicate the significant tumor ablation effect. Interestingly, a relatively stable proportion of both CD8+T and CD4+T cells in the peripheral blood is identified after tumor therapy in comparison with the decreased trend in the untreated group, representing an efficient antitumor immune response induced by the skin patch. The developed skin patch would provide a promising noninvasive approach for tumor therapies by direct tumor destruction and maintenance of the antitumor immune response. A flexible skin patch is proposed for noninvasive cryoablation, magnetic hyperthermia as well as immune response activation. The skin patch is verified with improved adhesiveness, conformable encapsulation, enhanced magnetic heating performance, and a systematical immune response regarding to CD4+and CD8+T cells. This noninvasive hybrid therapy is of great significance for tumor treatment and the activation of immune responses.

Recently, room‐temperature liquid metals have attracted increasing attention from researchers owing to their excellent material properties. Systematic interpretation of the potential toxicity issues involved is essential for a wide range of applications, especially in the biomedical and healthcare fields. However, even with the exponential growth of related studies, investigation of the toxicological impact and possible hazards of liquid metals to organisms is still in its infancy. This review aims to provide a comprehensive summary of the current frontier of knowledge on liquid metal toxicology and biocompatibility in different environments. Based on recent studies, this review focuses on Ga and Bi‐based in different states. It is necessary to evaluate their toxicity considering the rapid increase in research and utilization of such liquid metal composites. Finally, existing challenges are discussed and suggestions are provided for further investigation of liquid metal toxicology to clarify the toxicological mechanisms and strategies are provided to avoid adverse effects. In addition to resolving the doubts of public concern about the toxicity of liquid metals, this review is expected to promote the healthy and sustainable development of liquid metal‐based materials and their use in diverse areas, especially those related to health care. Toxicity is and will always be a big topic in the healthcare area. With the recent growth in investigations and applications of liquid metals, growing concerns about their potential safety issues are considered due to prior experiences of toxic mercury, which however are completely different. Summarizing the toxicity of liquid metals is beneficial to advance the sustainable development of liquid‐metal‐enabled biomedical applications.

Biocompatibility This cover image, highlighting article 2201924by Jing Liu and co‐workers, illustrates a beautiful landscape and ecosystem where liquid metals coexist in harmony with nature's flora and fauna: elks drink leisurely at the river side; fishes happily leap out of the water; and jellyfishes swim freely here and there. These scenes predict that more biocompatible liquid metals will be developed and play ever important roles in future society.

AbstractA new mechanism of thermonuclear reaction is briefly introduced. It shows that a certain amount of thermonuclear reaction can take place in dense, low temperature (T< 1 × 105K) plasmas. As most regions in the Sun are at moderate and low temperature, a sufficient amount of fusion energy is generated there. Therefore, the current standard solar models, in which the solar central temperature must be slightly lower than 15 × 106K, must be modified, and this would make the flux of high-energy neutrinos conform with the observational results.