Wearable and Implantable Devices for Healthcare.

Functional Materials and Devices for XR (VR/AR/MR) Applications

Advanced Functional Materials Solutions to Engineering the Neural Interface

Materials science is an inherently interdisciplinary research field, which involves physics, chemistry, and biology. The research of materials science emphasizes understanding a material's structure, and thus its properties and performance, through multiple capabilities ranging from synthesis, processing, and characterization to theory. As materials are the basic substances that make up all everyday objects, materials science is so important to nearly every aspect of science and technology in human existence and social life.

Flexible ferroelectric wearable devices for medical applications.

Programmable Materials.

XMU-100 Anniversary Special Issue.

Multidisciplinary Materials Research in KAIST Over the Last 50 Years

Bioinspiration Across All Length Scales of Materials.

Assembly of Materials Building Blocks into Integrated Complex Functional Systems

From Responsive Molecules to Interactive Materials.

Functional porous materials with intrinsic periodic (sub)nanometric pores, such as microporous zeolites, mesoporous silica, metal–organic frameworks (MOFs), and covalent organic frameworks (COFs), have found wide applications because of their excellent adsorption, separation, ion-exchange, and catalytic properties. The natural occurrence of zeolites was first discovered in 1756, with the aluminosilicate mineral stilbite, and their artificial synthesis began from the 1940s (Figure 1). The well-defined subnanometric micropores in zeolite frameworks provide an ideal void space (d < 2 nm) for guest molecules/ions to enter, diffuse, and exchange, making zeolites important modern adsorbents and detergents. In addition, the space confinement effect of zeolites, together with their tunable chemical composition, acidity, and active sites, makes zeolites the most important series of heterogeneous catalysts in today's petrochemical industry. In addition to these traditional applications, zeolites have recently shown great potential in emerging scenarios, such as biomass conversion, energy storage, CO2 capture and conversion, and host–guest assembly, representing new opportunities of zeolites in sustainable chemistry. Since the 1990s, the family of functional porous materials has been growing rapidly. The invention of mesoporous silica MCM-41 in 1992 has been well acknowledged as the beginning of the development of ordered mesoporous materials (Figure 1). In comparison with zeolites, mesoporous materials possess larger pores (2 nm < d < 50 nm) and more diverse chemical compositions (e.g., nonmetal oxides, metal oxides, pure metals, and carbons, etc.), which have found promising applications in catalysis, sensing, electronic devices, and drug delivery, etc. MOFs and COFs are relatively new members in the family of crystalline porous materials (Figure 1). Different from traditional porous materials that are built from the assembly of primary atoms, MOFs and COFs are constructed by the connection of inorganic/organic nodes and organic linkers via coordination or covalent bonds. By sophisticated selection of the building blocks, as well as the underlying network topology, the shapes and sizes of the nanopores in MOFs and COFs can be well controlled, making MOFs and COFs promising materials in applications such as gas separation and storage, energy conversion, biomedicine, and catalysis. In addition, porous carbon spheres, hollow multishelled structures, and crystalline porous organic salts have attracted much attention in the past several years because of their superior catalytic activities, electro-/photochemical properties, and ion conductivities. One of the main driving forces for the recent advances in functional porous materials is attributed to international collaborations and interdisciplinary integration. The inclusion of researchers from different countries/regions with diverse backgrounds and perspectives will foster in-depth interdisciplinary integration, significantly boosting the scientific innovation to tackle global problems. In 2017, the international collaboration project on "Functional Nanoporous Materials" was initiated in Jilin University, China. Under the framework of this project, an international collaboration network was established with the aim of addressing energy and environmental challenges via the design, synthesis, and application of functional porous materials. To date, more than 60 researchers from over 20 countries/regions have participated in this project, making important contribution to the recent prosperity of functional porous materials. To showcase the cooperation achievements in this research project, Advanced Materials and Angewandte Chemie launch a joint special issue on functional porous materials chemistry. The special issue of Advanced Materials features 18 reviews covering the synthesis, characterization, and application of various types of functional porous materials. The development in the synthetic chemistry lays the foundation for the recent progress in porous functional materials. In particular, the novel synthetic strategies for hierarchical (article number 2004690) and water-stable zeolites (article number 2003264), the synthesis of porous carbon spheres from polymer colloids (article number 2002475), the design of robust MOF networks with high connectivity (article number 2004414), and high-throughput and computer-aided approaches (article number 2002780), have promoted the discovery of a wide variety of porous materials. Meanwhile, advances in high-resolution and in situ characterization techniques, such as solid-state NMR (article number 2002879) and X-ray adsorption spectroscopy (article number 2002910), have given important clues to reveal the structure–property relationship of functional porous materials, providing important guidance for their applications in different scenarios. Catalysis is one of the most important applications of porous materials. In particular, the use of zeolites in a number of industrially important and sustainable catalytic processes has attracted much attention in the recent years, such as the catalytic conversion of C1 molecules (article number 2002927), non-oxidative methane dehydroaromatization (article number 2002565), and hydrogen generation from liquid chemical hydrogen-storage materials (article number 2001818). For MOFs, the storage and separation of H2, CO2, CH4, and hydrocarbons, etc., are the active research topics (article numbers 2002563 and 2002603). Besides these traditional applications, the electrochemistry of functional porous materials has recently become an emerging hot research area. Porous metals, metal oxides, or carbons can be made as electrocatalysts for important reactions such as hydrogen evolution and oxygen reduction (article number 2002435); zeolites, MOFs, COFs, and mesoporous nanomaterials can be used to construct electronic devices, such as capacitors, conductors, and electrodes in batteries and fuel cells (article numbers 2002038, 2002559, and 2004654). Meanwhile, hollow multishelled structures are emerging as promising photocatalysts for the degradation of pollutants, photocatalytic water splitting, CO2 reduction, and organic transformations (article number 2002556). Crystalline porous organic salts are another new type of functional porous materials, which have recently shown promising performance in proton conductivity, CO2 diffusion, molecular rotors, and energy transfer (article number 2003270). This special issue only highlights some of the recent progress in functional porous materials, and we can look forward to many exciting innovations in this area via collaboration and interdisciplinary integration, which will make a continuously growing impact on the sustainable development of our societies. Jihong Yu received her Ph.D. in inorganic chemistry from Jilin University in 1995 and worked as a postdoctoral fellow first at the Hong Kong University of Science and Technology and then at Tohoku University in Japan during 1996–1998. She has been a full professor in the Chemistry Department, Jilin University, since 1999. Her main research interest is in the designed synthesis and application of zeolitic nanoporous materials in energy, environment, and other emerging fields. Avelino Corma studied chemistry at the Universidad de Valencia (1967–1973) and received his PhD at the Universidad Complutense de Madrid in 1976 with Prof. Cortés. He was a postdoctoral researcher with Prof. Wojciechowski in the department of chemical engineering at Queen's University (Canada, 1977–1979). Since 1990, he has been a professor at the Instituto de Tecnologa Qumica (UPV-CSIC) at the Universidad Politécnica de Valencia. His current research focuses on the synthesis, characterization, and reactivity of acid–base and redox catalysis. Yi Li Yi Li received his Ph.D. degree from Jilin University in 2006, and joined the State Key Laboratory of Inorganic Synthesis and Preparative Chemistry at Jilin University as a lecturer. He was promoted to associate professor in 2009 and to full professor in chemistry in 2014. His research focuses on the computational chemistry and cheminformatics of functional nanoporous materials.

Advanced materials for heat energy transfer, conversion, storage and utilization, are very much at the forefront of academic and industrial interest. Within this context, we are delighted to provide cutting-edge insight into the emerging materials that promote the utilization of heat energy, via a special issue with a selection of 19 review and original research articles. These papers summarize the recent advances in thermoelectric materials, phononic metamaterials, thermal interfacial materials, nanomaterials, and the applications in thermal management and renewable energy. Thermoelectric materials are important for renewable energy technology. The thermoelectric performance is determined by the Seebeck coefficient, electrical conductivity, and thermal conductivity. The strong interaction between the different heat carriers, including phonons and electrons, complicates the optimization of thermoelectric efficiency. Yu et al. (article number 1904862) contribute a review paper that helps us understand the outstanding thermoelectric performance of main-group chalcogenides from a chemical bonding perspective. It is suggested that large valley degeneracy, band convergence, and high band anisotropy can result in high power factors. Moreover, compared to covalent and ionic bonds, the bonds in main-group chalcogenides are soft, causing large anharmonicity and low thermal conductivity. Zhao et al. (article number 1903867) present the recent advances in the structure and properties of liquid-like thermoelectrics, focusing on their unusual electron and phonon transport behaviors. Commonly adopted strategies for further improving the thermoelectric properties are also summarized. In addition to inorganic thermoelectric materials, bio-friendly organic thermoelectric materials are becoming promising candidates for thermoelectric devices. Zeng et al. (article number 1903873) introduce important advances in the experimental and theoretical studies of organic thermoelectric materials, including molecular junctions, organic-inorganic heterojunctions, and single-molecule magnet. Various optimization strategies for organic thermoelectric devices are discussed. In an independent review article, Wang et al. (article number 1904534) provide a survey of recent advances and emerging experimental and theoretical methodologies in probing and tuning thermal and thermoelectric transport in molecular junctions. Amorphous materials have valuable applications in thermoelectrics, thermal protection, flexible electronics, and artificial intelligence chips. Zhou et al. (article number 1903829) systematically review the fundamental physical aspects of thermal conductivity in amorphous materials and discussed a number of open problems. Shin et al. (article number 1904815) review the state-of-the-art of high temperature thermal materials used in thermal barrier coating, including dense materials and porous materials. In addition to a comprehensive list of high temperature thermal materials, the unique mechanisms governing thermal transport processes at high temperatures are also elucidated. Composites based on phase change materials have received tremendous attention due to their application in thermal energy storage and management. Yuan et al. (article number 1904228) systematically introduce the methods to manipulate the thermal conductivity of phase change materials. Considering the importance of conductive polymers and their composites in smart devices such as touch screen displays, health monitoring sensors, and functional clothing, Xu et al. (article number 1904704) provide a comprehensive summary of the thermal properties of conductive polymers. The fundamental thermal transport mechanisms, up-to-date advancements in regulating their thermal conductivity and thermal-related applications are addressed. The technology of phononic crystal provides a strategy for controlling the thermal conductivity of solids, with applications in new information technology, thermal management, and thermoelectrics. Sledzinska et al. (article number 1904434) provide a systematic review of the recent experimental achievements in the fabrication of phononic crystals and their applications in thermal management. Hussein et al. (article number 1906718) introduce the new emerging concept of nanophononic metamaterials, and provide a comprehensive comparison with nanophononic crystals. Although thermal conductivity reduction can be achieved in both, the underlying mechanism is different. Graphene has ultrahigh thermal conductivity, which is expected to be utilized in the thermal management of nanoscale electronic devices. More interesting, by coupling different physical quantities, graphene is also demonstrated in other applications, such as thermoacoustic coupling devices, thermoelectric coupling devices, and thermooptical coupling devices. Li et al. (article number 1903888) provide a review of the recent progress in graphene-based thermal devices. Although graphene has attracted a lot of attention in thermal management owing to its ultrahigh thermal conductivity, the thermal conductivity of graphene-based composites still needs to be improved. Barani et al. (article number 1904008) demonstrate remarkable enhancement in the thermal conductivity of the epoxy-based hybrid composites with graphene and Cu-NP fillers, whose effect is attributed to the formation of highly thermally conductive percolation networks. On the other hand, with the number of interfaces increasing, interfacial thermal resistance is becoming even more important than the channel material itself. Giri and Hopkins (article number 1903857) summarize the recent experimental and computational advances in thermal transport across solid/solid interfaces. The role of localized vibrational modes is also clarified. Meng and Wang (article number 1904796) introduce the development of antiscaling interfacial materials towards highly efficient heat energy transfer and discuss the various effects on thermal conductivity such as surface energy, surface roughness, and surface wettability. Since the first discovery of graphene, two dimensional (2D) materials opened up numerous competitive applications because of their unique and highly tunable physical and chemical properties. Zhao et al. (article number 1903929) provide a thorough understanding of the thermal transport properties of various 2D semiconductors, including transition metal dichalcogenides, black phosphorus, and SnSe. The phonon-governed applications, including thermoelectric power generation and photoelectric and thermal devices, are also addressed. The thermal properties of borophene are summarized by Li et al. (article number 1904349). Zhan et al. (article number 1903841) summarize the thermal properties of different 3D nanostructures ranging from 3D nanoarchitectures to metal–matrix composites, which are constructed from different nanomaterials including nanoparticles, nanotubes, nanowires, nanoribbons, and nanosheets. In recent years, one emerging concept in physics is “topological phononics.” Using 2D materials as examples, Liu et al. (article number 1904784) introduce the novel concepts of Berry phase, topology, and pseudospin for phonons. The corresponding phenomena in one- and three-dimensional systems are also covered. Another important feature in terms of the thermal properties of 2D materials is the unusually high heat radiation. Although the amount of heat energy carried by radiation is usually lower than that through conduction, a significant enhancement of five orders of magnitude are demonstrated in 2D materials, contributed by the hyperbolic electromagnetic dispersion. Baudin et al. (article number 1904783) discuss the possibility of radiation cooling in 2D materials, focusing on the graphene and hexagonal boron nitride heterostructures. They introduce the concepts and mechanism of super-Planckian thermal emission and electroluminescent cooling. In conclusion, we would like to thank the authors for providing their important contributions to this special issue. We greatly appreciate Dr. Huan Wang for organizing this special issue, as well as the whole editorial team of Advanced Functional Materials, for their great support and kind cooperation. We sincerely hope that the readers of Advanced Functional Materials will enjoy reading this special issue.

Liquid metals—that is, metals with low melting points—have fascinating and unique properties. Gallium is one of the most popular liquid metals because it melts near room temperature, has low toxicity, effectively zero vapor pressure, and can be combined with other metals to form alloys. The term "liquid metal" can be more broadly defined to include metals that melt at temperatures that are easy to access under common laboratory conditions. Room-temperature liquid metals open unique possibilities to leverage the soft, fluidic characteristics of liquids while simultaneously taking advantage of properties like high surface energy and thin oxide layers, high electrical and thermal conductivity, and other metallic characteristics that are typically reserved for rigid, solid materials. This liquid-metallic combination has resulted in remarkable properties, unusual behaviors, and new materials and devices that cannot be created with typical fluids or common metals alone. Interest in liquid metals has grown over the last decade due to the interest in applications that take advantage of their properties. For example, liquid metals can be used as conductors and components in soft and stretchable electronics. Likewise, they can be used for soft biomedical devices, energy harvesting devices, and e-textiles. Liquid metals can help catalyze reactions in unique ways and have interfacial properties that can be exploited for a variety of applications, such as actuators, batteries, and substrates for the deposition of thin films. The versatility of liquid metals presents many opportunities for future materials, devices, and systems, and represents an exciting paradigm for both scientific exploration and the creation of novel technologies. The special issue on Liquid Metals for Functional Materials consists of 49 manuscripts with 37 research articles and 12 reviews across a wide breadth of the liquid metal field. The work focuses on the latest advancements from fundamental properties to applied concepts, as broadly classified as Energy and Electrochemistry, Biomedical and Healthcare, Catalysts and Reactions, Composites and Multiphase Materials, Electronics and Conductors, Fabrication and Patterning, and Interfacial Properties. This collection highlights the multidisciplinary nature of liquid metal research and provides a platform to showcase our current understanding and outline future directions. We sincerely thank Dr. Joseph Krumpfer and Dr. Esther Levy, whose dedication to this special issue energized this effort and led to the exciting collection of papers presented in this special issue. Below, we will briefly highlight the contents of the special issue through the lens of several of the key subtopics in the field. Liquid metals offer promising potential in future energy storage and harvesting. Their electrical conductivity, deformability, compatibility with electrochemistry, lithium dissolution capability, and the possibility of creating porous composites make them ideal materials for efficient ion and electron exchanges. The addition of small metallic components can significantly alter the electrochemical behavior of liquid metals. In a work published in this special issue, Tang and co-workers showed the modulation of electrochemical properties by studying fractals that are formed from liquid metal alloys (adfm.202301348). In another work, Li and co-workers presented mixtures of MXene with EGaIn for energy-harvesting (adfm.202307830). Additionally, Boley and co-workers created a galvanic cell by mechanically rupturing surface oxide of liquid metals to convert chemical energy to electrical energy (adfm.202309177). Quality of electrical conductivity and stretchability are important factors in textile-based electronics with embedded supercapacitors, which are carefully investigated in another work by So and co-workers (adfm.202310318). An interesting paper by Deng and co-workers presented the application of liquid metals for forming elastomer seals in stretchable lithium-ion storage units (adfm.202309861). Finally, the special issue includes a review by Yan and co-workers on advances in energy storage based on liquid metal systems (adfm.202309706). The low toxicity of gallium-based liquid metals makes them suitable for medical applications. The use of liquid metals in these areas has been growing in popularity, and this issue features several papers that review recent biomedicine-related liquid metal works. For example, one paper by Seo and co-workers summarized the use of low-melting-point metals for biomedical applications (adfm.202307708). One paper by Park and co-workers reviewed the usage of gallium-based liquid metals for bioelectronics (adfm.202307990) while another paper by Lim and co-workers reviewed healthcare-related applications of liquid metals in wearables and soft robotics (adfm.202309989). Additionally, Wei and co-workers reviewed liquid metal-based biosensors (adfm.202308173). In more specific applications, Truong and co-workers created silver-gallium amalgamated particles that show antibacterial properties and show promise as a spray-coating on implantable devices (adfm.202310539). In another work by Markvicka and co-workers, composites of elastomers and liquid metals were developed with acoustic properties that improve the image quality of wearable ultrasound devices for long-term patient monitoring (adfm.202308954). Additionally, liquid-metal electrodes and particles were used by Kim and co-workers to create soft biosensors capable of detecting ascorbic and uric acid, dopamine, and glucose (adfm.202311696). Currently, a significant portion of global greenhouse emissions and energy consumption stems from industrial-scale chemical reactions used in the production of ammonia, fuel, hydrogen, polymers, and other chemicals. Progress in enhancing catalysis and reaction rates using solid materials has been limited. Exploring the untapped properties of liquid metals holds great promise for introducing new paradigms in these chemical processes. Researchers offered several interesting works in this special issue on catalysts and reactions using liquid metals. Here, Daeneke and co-workers showed a delicate liquid metal system with incorporated copper for electrocatalytic oxidation of ethanol (adfm.202304248). Kalantar-Zadeh and co-workers demonstrated that liquid metal can be used as the reservoir for zinc metal for sourcing it into the synthesis metal–organic frameworks (adfm.202300969). While another study put forward by Yarema and co-workers presented an approach to use liquid metal to create Pd-Zn nanocrystals (adfm.202309018). In another seminal manuscript, Sitti and co-workers utilized liquid metal initiated polymerization to create hydrogel composites (adfm.202308238). A liquid metal reaction media was also used by Zavabeti and co-workers for the creation of atomically thin bismuth oxides that enabled strong piezoelectric systems (adfm.202307348). O'Mullane and co-workers showed that liquid metals have a potential use in plasma-assisted carbon dioxide reduction by incorporating liquid metal droplets (adfm.202307846). The capabilities of liquid metals are not just limited to inorganic systems. Miyako and co-workers showed that liquid metal catalysts can also be effectively used in immunostimulants (adfm.202305886). Liquid metal can be combined with diverse components such as polymers, metals, carbon-based materials, or other organic or inorganic materials to create composites and multiphase systems. This can create novel composites with enhanced functional or mechanical properties relative to solid-based inclusions or other phases can be added into liquid metal to provide new properties not native to liquid metal. These concepts were well captured in the special issue. One review by Kramer-Bottiglio and co-workers focused on multiphase composites containing liquid metal and other (x) fillers for unique combinations of properties (adfm.202309529) while another review by Lee and co-workers showed how adding particles into liquid metal can create magnetic liquid metal (adfm.202311153). A third review by Tee and co-workers discussed liquid metal composites for wearable electronics (adfm.202400284). Additionally, a set of papers presented liquid-metal polymer composites with different functionalities. One work by Bartlett and co-workers showed how liquid-metal droplets in elastomers could create electrically conductive reversible adhesives for soft electronics (adfm.202304101), while another by Li and co-workers showed hydrogel composites with high toughness and conductivity (adfm.202308113). This polymer composite architecture also enabled thermally stable soft materials for high-temperature applications as presented by Majidi and co-workers (adfm.202309725) while Zhou and co-workers used liquid metal droplets as cross-links to enable recyclable conductive composites (adfm.202308032). The high deformability of liquid metal wires was also used in conjunction with a magnetic soft composite by Park and co-workers to create artificial muscles (adfm.202302895). Like solid metals, liquid metals have a high electrical conductivity, making them suitable as conductors in electronics, but with the added properties of liquids, such as discretization into droplets. One review by Hussain and co-workers examined liquid-metal droplets and their use for electronics such as sensors, switches, transistors, actuators, and more (adfm.202308116). Liquid metals are also especially suitable for soft, flexible, and stretchable electronics. Toward this, Zhang and co-workers created a soft, lightweight composite with networks of liquid-metal fibers (adfm.202308128) while Zhang and co-workers developed liquid-metal composite materials that show increased conductivity with applied strain (adfm.202310225). In another contribution, Zheng and co-workers demonstrated a permeable and stretchable liquid-metal fibers for sensors and other electronics (adfm.202308120). Bartlett and co-workers presented a liquid metal-based conductive adhesive for integration of soft electronics and rigid devices (adfm.202313567) while Hjort and co-workers presented a laser engraving methodology for creating liquid metal-based interconnects (adfm.202309707). Other papers in this issue describe the use of liquid metals in specific electronic devices. One review presented by Park and co-workers examined liquid-metal systems that respond to a variety of stimuli, and that can be used for electronics such as wearable sensors (adfm.202308703). The compliant nature of liquid metal was used by Lacour and co-workers to make sensors that can measure softness (adfm.202308698). A liquid-metal inductive sensor was created by Jeong and co-workers that is capable of distinguishing between various stimuli on a finger (adfm.202305776), and a wearable liquid-metal antenna was directly printed by Hashimoto and co-workers (adfm.202311219). Liquid metals can be patterned into useful shapes such as circuits, antennas, and wires to create soft and stretchable analogs to existing electronic devices. Relative to conventional metals, such as copper or aluminum, the fluidic nature of liquid metal allows it to be patterned in unique ways, including injection and 3D printing. In many cases, patterning is facilitated by the thin, solid oxide layer that forms rapidly on the surface of liquid metals in the presence of oxygen. This solid oxide "skin" allows the liquid metal to retain shapes that would normally be impossible with liquids due to surface tension. This special issue offers several interesting works on the fabrication and patterning of liquid metals. Liquid metals were 3D printed in ceramics by Yang and co-workers for use in microwave absorption (adfm.202307499). In another example, Syed and co-workers separated the oxide layer from the liquid metal to enable the fabrication of gas sensors (adfm.202309342). Park and co-workers also took advantage of the ability to use liquid metal particles to pattern stretchable electronics (adfm.202309660). The particles can be used to make thermally conductive composites as demonstrated by Lee and co-workers (adfm.202306698) or be cast as a film and subsequently merged together to form conductive traces as presented by Dickey and co-workers (adfm.202308574). Liquid metals have remarkable interfacial properties. For example, they have the largest interfacial tension of any liquid at room temperature, with values nearly an order of magnitude larger than that of water. Yet, the surface tension effectively can be lowered to near zero by using electrochemical oxidation. This phenomenon, as well as several others, can be used to control the flow and shape of liquid metal, as reviewed by Wang and co-workers in this special issue (adfm.202309614). In addition, studies by Daniels and co-workers provide new insights into this electrochemical phenomenon by carefully measuring the tension as a function of electrical potential (adfm.202311501) or by confining the metal to porous tubes as demonstrated by Khan and co-workers (adfm.202307919). Another interesting property of liquid metals is that they can react to form surface oxides on their surface. Herein, Tabor and co-workers enhance the mechanical strength of the skin by depositing thin silica layers on the oxide (adfm.202308167). Further, Elbourne and co-workers evaluated the structure of the oxide on liquid metal droplets (adfm.202310147) while Koo and co-workers utilized the oxide-coated liquid metal to form more stable solar cells (adfm.202311597). We are grateful for all the authors, reviewers, and editors who made this special issue possible. We hope this special issue will help highlight the challenges and exciting opportunities for the development and utilization of liquid metal in diverse applications. M.D.B., M.D.D., A.T.O., and K.K-Z. contributed equally to this work. The authors declare no conflict of interest Michael D. Bartlett is an associate professor and John R. Jones III Faculty Fellow of Mechanical Engineering at Virginia Tech. He received his B.S.E. from the University of Michigan, Ph.D. from the University of Massachusetts Amherst, and was a postdoctoral fellow at Carnegie Mellon University. Michael leads the Soft Materials and Structures Lab, which investigates multifunctional soft materials and composites with highly controllable mechanical and functional properties for the creation of soft electronics and robotics based on liquid metal, switchable and intelligent adhesives, and adaptive materials. Michael Dickey is the Camille and Henry Dreyfus Professor in the Department of Chemical & Biomolecular Engineering at NC State University. He received a B.S. in chemical engineering from Georgia Institute of Technology (1999) and a Ph.D. from the University of Texas (2006) under the guidance of Professor Grant Willson. From 2006 to 2008, he was a post-doctoral fellow in the lab of Professor George Whitesides at Harvard University. He completed a sabbatical at Microsoft in 2016 and EPFL in 2023. Michael's research interests include soft matter (liquid metals, gels, polymers) for soft and stretchable devices (electronics, energy harvesters, and soft robotics). Aaron Ohta is a professor in the Department of Electrical and Computer Engineering at the University of Hawaii at Manoa. He received his B.S. degree from the University of Hawaii at Manoa, his M.S. degree from the University of California, Los Angeles, and his Ph.D. degree from the University of California, Berkeley, all in electrical engineering. Aaron's research interests include reconfigurable circuits and systems using liquid metals and other materials, microfluidics, and microelectromechanical systems (MEMS). Kourosh Kalantar-Zadeh is a professor and Head of School of Chemical and Biomolecular Engineering at the University of Sydney. He is involved in research in the fields of analytical chemistry, materials sciences, gastroenterology, electronics, and sensors. Professor Kalantar-Zadeh is best known for his works on ingestible sensors, liquid metals, and 2D semiconductors. He led his group to the invention of an ingestible chemical sensor: human gas sensing capsule, one of the breakthroughs in the field of medical devices. He has received several international awards for his scientific contributions including the 2017 IEEE Sensor Council Achievement, and 2020 Robert Boyle Prize of RSC.

Supramolecular Wearable Sensors

Drug delivery systems (DDS) have been the focus of intense research for several decades. Many approaches and strategies have been employed over the years, further expanding this field. For example, the advancements towards targeted drug delivery (TDD) enabled the use of DDS for diagnostic purposes. In addition, DDS research has provided the foundation for tissue engineering and theranostic systems (therapeutic systems with diagnostic properties). Drug delivery research has yielded many successes over the years with a significant amount of therapeutic and diagnostic products out in the market. Nevertheless, many challenges still remain. Herein, in this special edition, we asked various experts to review recent advancements in their field of expertise and report their latest findings. The special edition is well balanced and is comprised of 60% reviews and 40% research articles. One may find up-to-date reviews on advancements made in biomaterials, noninvasive drug delivery, drug conjugations, biosensors, diagnostics, implantable and ingestible devices, nanomaterials, cancer treatment, and endosome-derived vesicles. Additionally, research articles are provided, describing advanced new designs of microneedles (MNs), approaches to enhance tissue engineering capabilities, biomaterials, and DDS. The global market of protein- and nucleotide- based pharmaceutics accounted for $643 million in 2016, and is anticipated to reach over $8000 million by 2028. However, the use of these therapeutics is hindered by issues of immunogenicity, high molecular weight, fast renal clearance, and enzymatic degradation. For these reasons, to date, monoclonal antibodies (mAbs) are administered only via injection. Considering that, Angsantikul et al. propose the use of ionic liquid and eutectic solvent for the oral delivery of mAbs (article number 2002912). Their system reduced the mucosal viscosity and enhanced the paracellular transport of TNFα antibody in vitro. Additionally, Rondon and colleagues review the latest advancements in polymer chemistry and protein engineering in order to overcome part of these limitations (article number 2101633). Another approach to overcome these limitations is by using antibody-drug conjugates (ADCs). Accordingly, Firer and Luboshits review the recent developments employed in ADCs for the treatment of hematological malignancies (article number 2100032). They focus on the important link between the biology of the ADC and clinical efficacy, highlighting newer developments that strengthen this link to provide long-term clinical benefits. One of the most important purposes of drug delivery is achieving TDD. Dacoba and colleagues provide an overview on the concepts of passive and active targeting while exploring current venues for nanotechnology to solve the problems associated with drug delivery (article number 2009860). TDD is especially important for cancer therapy since killing cancerous cells is quite facile, but killing only cancerous cells is extremely challenging. Fu et al. review the latest strategies employed to overcome the barriers of chimeric antigen receptor T cells therapy in solid tumors (article number 2009489). Brain therapy is another challenging route for drug delivery requiring specific TDD system. To this end, Buaron et al. have developed a novel pectic galactan-based gene therapy approach that targets reactive gliosis via specific carbohydrate interaction between galactan and Gal-3 (article number 2100643). Their biocompatible pectin galatcan-plasmid DNA complexes were selectively transfected to glial cells in cortical lesions. Moreover, Avital et al. report their interesting application for nanosized DDS—foliar delivery of siRNA for treating grapevine leafroll associated virus-3 (GLRaV-3) infection that causes major economic losses (article number 2101003). By exploiting a lipid-modified polyethylenimine carrier, they show that a single dose can knock down GLRaV-3 titer, and multiple doses keeps the viral titer at baseline, which triggers the recovery of the vine and berries. Another important aspect of drug delivery research is the development of noninvasive drug administration routes. Rahamim and Azagury review the origins of biomimetic, bioinspired, and bioengineered noninvasive DDS and achievements made in the last decade (article number 2102033). Additionally, Zhang et al. review advances in DDS that access the ear through the tympanic membrane (article number 2008701). Transdermal drug delivery is one of the most used noninvasive drug delivery routes. An exciting approach for transdermal drug delivery is microneedles (MNs). Puigmal and colleagues propose applying MNs array to treat severe burns that simultaneously sample immune cells in the interstitial fluid to diagnose the response (article number 2100128). Their MNs design enables the local delivery of pharmaceutics—the chemokine CCL22 and the cytokine IL-2—thus increasing local immuno-suppression. They found that the immune cell population in the allograft and MN were similar so they can be harvested from the MN for downstream analysis. Moreover, Li et al. have also proposed an improved MNs design where they use a biphasic dissolvable MN patch with water-insoluble backing in order to tackle insufficient drug delivery with MN (article number 2103359). Their new design enables a drug delivery efficiency of >90% into the skin within 5 min. Biomaterials are the building blocks of drug delivery, diagnostics, and tissue engineering research. Therefore, there is an ever-growing need for novel biomaterials with new functionalities and improved properties. To this end, Arun et al. present an exclusive coverage of biocompatible injectable pasty or liquid polymers without the use of any solvent for drug delivery and regenerative medicine applications (article number 2010284). Moreover, Khait et al. review novel biomaterial-based strategies used to modulate the immune response post ischemic stroke while providing their perspective on the potential clinical translation of these therapies (article number 2010674). Additionally, Redenski et al. developed a new composite tissue made of soft-tissue matrices and decellularized bone for bone defect repair (article number 2008687). The use of their novel tissue composite supported a long-term bone defect repair, as well as muscle defect bridging. These aforementioned applications and additional applications use cell-based therapeutics. The major obstacles of cell-based therapeutics are their low yields (i.e., difficult to scale-up), insufficient drug loading, and inconsistencies. For this reason, Guo et al. have developed a scaled-up and facile magnetic-based extrusion method for preparing endosome-derived vesicles (article number 2008326). An additional application of diagnostics and therapeutics is implantable and ingestible devices. In this special edition, Yang and colleagues provide an up-to-date review on the state-of-the-art of powering technologies for implantable and ingestible electronics—one of the greatest challenges for ingestible devices (article number 2009289). Welch et al. have focused their review on the complex hierarchical nano-structures and nano-materials used in biosensors and diagnostic technologies (article number 2104126). Additionally, they discuss their unique advantages and clinical applications while proposing future directions. In this special edition Nakonechny and Nisnevitch provide an up-to-date review focused on ultrasound applications used to combat infections caused by microorganisms, and to promote the local release of antimicrobial drugs from liposomes and medical implants (article number 2011042). Precise and well-controlled scaffolds are highly desired for tissue engineering and regenerative medicine purposes. For example, Dubay et al. review the recent achievements of single-cell microgels and their potential alternatives, which are used when single cell resolution is needed, for example—modular bio-inks and 3D cellular microenvironments (article number 2009946). Another challenge for implantable devices is a foreign body response (FBR). Kutner et al. review the recent advantageous technologies used to overcome the FBR effect via surface modifications and localized DDS (article number 2010929). One such surface modification is reported by Israeli et al. who developed a general and versatile technology to engineer light-responsive protein-based biomaterials (article number 2011276). These novel biomaterials—consist of azobenzene containing elastin-like polypeptides—are capable of forming self-assembled nanostructures and exhibit a reversible, light-mediated phase transition, with up to a 12 °C difference in the transition temperature. We are certain that this assemblage of reviews and research papers on the use of DDS for therapeutic and diagnostic purposes is of high interest for anyone working in this field. It provides up-to-date reviews on state-of-the-art topics and research papers with promising results to further propel drug delivery research. Understanding what has been done in the past, while learning of new approaches and techniques, is crucial for any scholar who wishes to advance their personal research. Joseph Kost D.Sc. is a University Distinguished Professor, he holds The Abraham and Bessie Zacks Chair in Biomedical Engineering and was the Dean of the Faculty of Engineering Sciences at Ben-Gurion University of the Negev (BGU). He is a member of AIMBE, NAE, CRS, and the Israel Academy of Sciences and Humanities. His research interests are in the fields of biomedical engineering, biomaterials science, controlled drug delivery, gene therapy, and ultrasound. Edith Mathiowitz is a full Professor of Medical Science and Engineering at Brown University, Department of Department of Pathology and Laboratory Medicine. She Is an AIMBE, CRS, and NAI fellow member. She founded and directed the ABC/Biotechnology Graduate Program at Brown. Her interdisciplinary research is focused on developing smart oral bioadhesive delivery systems and novel insights in polymer morphology. Her laboratory serves as an incubator for several start-up companies such as Spherics, Perosphere, and Therapyx. Aharon (Roni) Azagury is an Assistant Professor in the Department of Chemical and Biotechnology Engineering in Ariel University. He received his PhD in chemical engineering from BGU. He is a member of the CRS, ICRS, and NAI societies. His current research focuses on developing novel noninvasive biomimetic and bioinspired drug delivery systems.