Magnetoresponsive liposomes applications in nanomedicine: A comprehensive review

Safe and effective cancer therapy requires a suitable nanocarrier that can target particular sites, such as cancer cells, in a selective manner. With the tremendous growth in nanotechnology, liposomes, among various competing nanocarriers, have shown promising advances in cancer therapy. Magnetic nanoparticles and metal ions are wide-reaching candidates for conferring magnetic properties and for incorporation into liposomes. Combining liposomes with magnetic structures enables construction of magnetoresponsive liposomes, allowing stimuli-responsiveness to an alternating magnetic field, magnetic targeting, and tracking by magnetic resonance imaging, which could all occur in parallel. This review presents a comprehensive analysis of the practical advances and novel aspects of design, synthesis and engineering magnetoresponsive liposomes, emphasizing their diverse properties for various applications. Our work explores the innovative uses of these structures, extending beyond drug delivery to include smart contrast agents, cell labeling, biosensing, separation, and filtering. By comparing new findings with earlier studies, we showcase significant improvements in efficiency and uncover new potentials, setting a new benchmark for future research in the field of magnetoresponsive liposomes.

Implantable Triboelectric Nanogenerators for Self-Powered Cardiovascular Healthcare

Triboelectric nanogenerators (TENGs) have gained significant traction in recent years in the bioengineering community. With the potential for expansive applications for biomedical use, many individuals and research groups have furthered their studies on the topic, in order to gain an understanding of how TENGs can contribute to healthcare. More specifically, there have been a number of recent studies focusing on implantable triboelectric nanogenerators (I-TENGs) toward self-powered cardiac systems healthcare. In this review, the progression of implantable TENGs for self-powered cardiovascular healthcare, including self-powered cardiac monitoring devices, self-powered therapeutic devices, and power sources for cardiac pacemakers, will be systematically reviewed. Long-term expectations of these implantable TENG devices through their biocompatibility and other utilization strategies will also be discussed.

Tissue-Matchable and Implantable Batteries Toward Biomedical Applications

Implantable electronic devices can realize real-time and reliable health monitoring, diagnosis, and treatment of human body, which are expected to overcome important bottlenecks in the biomedical field. However, the commonly used energy supply devices for them are implantable batteries based on conventional rigid device design with toxic components, which both mechanically and biologically mismatch soft biological tissues. Therefore, the development of highly soft, safe, and implantable tissue-matchable flexible batteries is of great significance and urgency for implantable bioelectronics. In this work, the recent advances of tissue-matchable and implantable flexible batteries are overviewed, focusing on the design strategies of electrodes/batteries and their biomedical applications. The mechanical flexibility, biocompatibility, and electrochemical performance in vitro and in vivo of these flexible electrodes/batteries are then discussed. Finally, perspectives are provided on the current challenges and possible directions of this field in the future.

Outstanding Robust Photo- and Thermo-Electric Applications with Stabilized n-Doped Carbon Nanotubes by Parylene Coating

Stabilization techniques for n-doped carbon nanotubes (CNTs) are essential for the practical use of CNT devices. However, none of the reported n-dopants have sufficient robustness in a practical environment. Herein, we report a highly stable technique for fabricating n-doped CNT films. We elucidate the mechanism by which air stability can be achieved by completely covering CNTs with n-dopants to prevent oxidation; consequently, the stability is lost when exposed to scratches or moisture. Therefore, we introduce parylene as a protective layer for n-doped CNTs and achieve air stability for more than 365 d. Moreover, we demonstrate outstanding robust thermo-electric power generation from strong acids, alkalis, and alcohols, which cannot be realized with conventional air-stable n-dopants. The proposed stabilization technique is versatile and can be applied to various n-dopants. Thus, it is expected to be a key technology in the practical application of CNT devices.

Triboelectric Nanogenerators as Power Sources for Chemical Sensors and Biosensors

The recent advances of portable sensors in flexible and wearable form factors are drawing increasing attention worldwide owing to their requirement applications ranging from health monitoring to environment monitoring. While portability is critical for these applications, real-time data gathering also requires a reliable power supply-which is largely met with batteries. Besides the need for regular charging, the use of toxic chemicals in batteries makes it difficult to rely on them, and as a result different types of energy harvesters have been explored in recent years. Among these, triboelectric nanogenerators (TENGs) provide a promising platform for harnessing ambient energy and converting it into usable electric signals. The ease of fabrication and possibility to develop TENGs with a diverse range of easily available materials also make them attractive. This review focuses on the TENG technology and its efficient use as a power source for various types of chemical sensors and biosensors. The paper describes the underlying mechanism, various modes of working of TENGs, and representative examples of their utilization as power sources for sensing a multitude of analytes. The challenges associated with their adoption for commercial solutions are also discussed to stimulate further advances and innovations.

Redox-Transition from Irreversible to Reversible Vitamin C by Pore Confinement in Microporous Carbon Network

Enhancement of redox-reversibility in electroactive species has been studied because of fundamental interest and their importance for energy storage systems. Various electroactive molecules suffer from redox-irreversible behavior, and this is a critical reason for their exclusion as redox electrolytes in energy storage systems. In this article, we fully demonstrated that ascorbic acid (ASC), which is an abundant but redox-irreversible molecule, can become redox-reversible when it is confined in microporous carbon regimes. From a theoretical perspective, redox-reversibility in an electrochemical reaction coupled with an irreversible chemical process can be greatly enhanced due to kinetic acceleration toward the inverse direction of the chemical reaction by accumulation of products in the nanoconfined regime. However, the kinetic acceleration in a nanoconfined domain shows limitations for enhancing the redox-reversibility, which indicates that stabilization of the species undergoing an irreversible chemical process is another important factor for redox-reversibility enhancement. The origin of nanoporous confinement of ASC and its enhanced redox-reversibility was rationalized by molecular dynamics simulations. We found that ASC-clusters of a fully protonated ASC and its conjugated base formed inside carbon pores, which would be a main driving force for its confinement in microporous carbon networks. Lastly, we demonstrated a prototype energy storage device using redox-reversible ASC in microporous carbon as the half electrode, which shows the feasibility of ASC as a possible redox electrolyte in an aqueous energy storage system.

Self-Powered Active Sensing Based on Triboelectric Generators

The demand for portable and wearable chemical or biosensors and their expeditious development in recent years has created a scientific challenge in terms of their continuous powering. As a result, mechanical energy harvesters such as piezoelectric and triboelectric generators (TEGs) have been explored recently either as sensors or harvesters to store charge in small, but long-life, energy-storage devices to power the sensors. The use of energy harvesters as sensors is particularly interesting, as with such multifunctional operations it is possible to reduce the number devices needed in a system, which also helps overcome the integration complexities. In this regard, TEGs are promising, particularly for energy autonomous chemical and biological sensors, as they can be developed with a wide variety of materials, and their mechanical energy to electricity conversion can be modulated by various analytes. This review focuses on this interesting dimension of TEGs and presents various self-powered active chemical and biological sensors. A brief discussion about the development of TEG-based physical, magnetic, and optical sensors is also included. The influence of environmental factors, various figures of merit, and the significance of TEG design are explained in context with the active sensing. Finally, the key applications, challenges, and future perspective of chemical and biological detection via TEGs are discussed with a view to drive further advances in the field of self-powered sensors.

Skin bioelectronics towards long-term, continuous health monitoring

Skin bioelectronics are considered as an ideal platform for personalised healthcare because of their unique characteristics, such as thinness, light weight, good biocompatibility, excellent mechanical robustness, and great skin conformability. Recent advances in skin-interfaced bioelectronics have promoted various applications in healthcare and precision medicine. Particularly, skin bioelectronics for long-term, continuous health monitoring offer powerful analysis of a broad spectrum of health statuses, providing a route to early disease diagnosis and treatment. In this review, we discuss (1) representative healthcare sensing devices, (2) material and structure selection, device properties, and wireless technologies of skin bioelectronics towards long-term, continuous health monitoring, (3) healthcare applications: acquisition and analysis of electrophysiological, biophysical, and biochemical signals, and comprehensive monitoring, and (4) rational guidelines for the design of future skin bioelectronics for long-term, continuous health monitoring. Long-term, continuous health monitoring of advanced skin bioelectronics will open unprecedented opportunities for timely disease prevention, screening, diagnosis, and treatment, demonstrating great promise to revolutionise traditional medical practices.

Environment-friendly degradable zinc-ion battery based on guar gum-cellulose aerogel electrolyte

With the vigorous development of electronics and the increasingly prominent problem of environmental pollution, it is particularly important to exploit environmentally friendly electronic devices. Transient electronics represent a kind of device that once the specified functions have completed can completely or partially disappear through physical or chemical actions. In this work, we introduce a novel guar gum-cellulose aerogel (GCA) membrane based on natural biomaterials and successfully use it as an electrolyte film to fabricate a degradable zinc-ion battery (DZIB). All components of the prepared DZIBs can be successfully degraded or disintegrate in phosphate-buffered saline (PBS) containing a solution of proteinase K after approximately 40 days. This electrolyte film has a high ionic conductivity of approximately 4.73 × 10^-2 S cm^-1 and a good mechanical stress property. When applied to DZIB, the production of zinc dendrites can be restrained, leading to the battery showing excellent electrochemical performance. The battery exhibits a specific capacity of 309.1 mA h g^-1 at a current density of 308 mA g^-1 after 100 cycles and a steady cycling ability (100% capacity retention after 200 cycles). More importantly, the electrochemical performance of DZIB is better than that of transient batteries reported in the past, taking a solid step in the field of transient electronics in the initial stage.

N-Doped celery-based biomass carbon with tunable Co3O4 loading for enhanced-performance of solid-state supercapacitors

N-doped celery-based biomass carbon with tunable Co3O4 loading is prepared and shows enhanced specific capacitance.

Enhancement of Bone Regeneration Through the Converse Piezoelectric Effect, A Novel Approach for Applying Mechanical Stimulation

Serious bone injuries have devastating effects on the lives of patients including limiting working ability and high cost. Orthopedic implants can aid in healing injuries to an extent that exceeds the natural regenerative capabilities of bone to repair fractures or large bone defects. Autografts and allografts are the standard implants used, but disadvantages such as donor site complications, a limited quantity of transplantable bone, and high costs have led to an increased demand for synthetic bone graft substitutes. However, replicating the complex physiological properties of biological bone, much less recapitulating its complex tissue functions, is challenging. Extensive efforts to design biocompatible implants that mimic the natural healing processes in bone have led to the investigation of piezoelectric smart materials because the bone has natural piezoelectric properties. Piezoelectric materials facilitate bone regeneration either by accumulating electric charge in response to mechanical stress, which mimics bioelectric signals through the direct piezoelectric effect or by providing mechanical stimulation in response to electrical stimulation through the converse piezoelectric effect. Although both effects are beneficial, the converse piezoelectric effect can address bone atrophy from stress shielding and immobility by improving the mechanical response of a healing defect. Mechanical stimulation has a positive impact on bone regeneration by activating cellular pathways that increase bone formation and decrease bone resorption. This review will highlight the potential of the converse piezoelectric effect to enhance bone regeneration by discussing the activation of beneficial cellular pathways, the properties of piezoelectric biomaterials, and the potential for the more effective administration of the converse piezoelectric effect using wireless control.

A photo-curable gel electrolyte ink for 3D-printable quasi-solid-state lithium-ion batteries

3D printing technologies have been adapted to enable the fabrication of lithium-ion batteries (LIBs), allowing flexible designs such as micro-scale 3D shapes. Here, we demonstrate 3D-printable gel electrolytes, printed at room temperature. The electrolyte gel solidified by UV irradiation maintains its structural integrity and high lithium-ion conductivity, enabling fully 3D-printed quasi-solid-state LIBs.

Ultrasound-Powered Implants: A Critical Review of Piezoelectric Material Selection and Applications

Ultrasound-powered implants (UPIs) represent cutting edge power sources for implantable medical devices (IMDs), as their powering strategy allows for extended functional lifetime, decreased size, increased implant depth, and improved biocompatibility. IMDs are limited by their reliance on batteries. While batteries proved a stable power supply, batteries feature relatively large sizes, limited life spans, and toxic material compositions. Accordingly, energy harvesting and wireless power transfer (WPT) strategies are attracting increasing attention by researchers as alternative reliable power sources. Piezoelectric energy scavenging has shown promise for low power applications. However, energy scavenging devices need be located near sources of movement, and the power stream may suffer from occasional interruptions. WPT overcomes such challenges by more stable, on-demand power to IMDs. Among the various forms of WPT, ultrasound powering offers distinct advantages such as low tissue-mediated attenuation, a higher approved safe dose (720 mW cm^-2 ), and improved efficiency at smaller device sizes. This study presents and discusses the state-of-the-art in UPIs by reviewing piezoelectric materials and harvesting devices including lead-based inorganic, lead-free inorganic, and organic polymers. A comparative discussion is also presented of the functional material properties, architecture, and performance metrics, together with an overview of the applications where UPIs are being deployed.

Degradation Behavior, Biocompatibility, Electrochemical Performance, and Circularity Potential of Transient Batteries

Transient technology seeks the development of materials, devices, or systems that undergo controlled degradation processes after a stable operation period, leaving behind harmless residues. To enable externally powered fully transient devices operating for longer periods compared to passive devices, transient batteries are needed. Albeit transient batteries are initially intended for biomedical applications, they represent an effective solution to circumvent the current contaminant leakage into the environment. Transient technology enables a more efficient recycling as it enhances material retrieval rates, limiting both human and environmental exposures to the hazardous pollutants present in conventional batteries. Little efforts are focused to catalog and understand the degradation characteristics of transient batteries. As the energy field is a property-driven science, not only electrochemical performance but also their degradation behavior plays a pivotal role in defining the specific end-use applications. The state-of-the-art transient batteries are critically reviewed with special emphasis on the degradation mechanisms, transiency time, and biocompatibility of the released degradation products. The potential of transient batteries to change the current paradigm that considers batteries as harmful waste is highlighted. Overall, transient batteries are ready for takeoff and hold a promising future to be a frontrunner in the uptake of circular economy concepts.

Development of Magnesium Anode-Based Transient Primary Batteries

Biodegradable primary batteries, also known as transient batteries, are essential to realize autonomous biodegradable electronic devices with high performance and advanced functionality. In this work, magnesium, copper, iron, and zinc - metals that exist as trace elements in the human body - were tested as materials for biomedical transient electronic devices. Different full cell combinations of Mg and X (where X = Cu, Fe, and Zn and the anodized form of the metals) with phosphate buffered saline (PBS) as electrolyte were studied. To form the cathodes, metal foils were anodized galvanostatically at a current density of 2.0 mA cm-2 for 30 mins. Electrochemical measurements were then conducted for each electrode combination to evaluate full cell battery performance. Results showed that the Mg-Cuanodized chemistry has the highest power density at 0.99 mW/cm2 . Nominal operating voltages of 1.26 V for the first 0.50 h and 0.63 V for the next 3.7 h were observed for Mg-Cuanodized which was discharged at a current density of 0.70 mA cm-2 . Among the materials tested, Mg-Cuanodized exhibited the best discharge performance with an average specific capacity of 2.94 mAh cm-2 , which is comparable to previous reports on transient batteries.

Emerging intraoral biosensors

Biomedical devices that involved continuous and real-time health-care monitoring have drawn much attention in modern medicine, of which skin electronics and implantable devices are widely investigated. Skin electronics are characterized for their non-invasive access to the physiological signals, and implantable devices are superior at the diagnosis and therapy integration. Despite the significant progress achieved, many gaps remain to be explored to provide a more comprehensive overview of human health. As the connecting point of the outer environment and human systems, the oral cavity contains many unique biomarkers that are absent in skin or inner organs, and hence, this could become a promising alternative locus for designing health-care monitoring devices. In this review, we outline the status of the oral cavity during the communication of the environment and human systems and compare the intraoral devices with skin electronics and implantable devices from the biophysical and biochemical aspects. We further summarize the established diagnosis database and technologies that could be adopted to design intraoral biosensors. Finally, the challenges and potential opportunities for intraoral biosensors are discussed. Intraoral biosensors could become an important complement for existing biomedical devices to constitute a more reliable health-care monitoring system.

Multifunctional Batteries: Flexible, Transient, and Transparent

The primary task of a battery is to store energy and to power electronic devices. This has hardly changed over the years despite all the progress made in improving their electrochemical performance. In comparison to batteries, electronic devices are continuously equipped with new functions, and they also change their physical appearance, becoming flexible, rollable, stretchable, or maybe transparent or even transient or degradable. Mechanical flexibility makes them attractive for wearable electronics or for electronic paper; transparency is desired for transparent screens or smart windows, and degradability or transient properties have the potential to reduce electronic waste. For fully integrated and self-sufficient systems, these devices have to be powered by batteries with similar physical characteristics. To make the currently used rigid and heavy batteries flexible, transparent, and degradable, the whole battery architecture including active materials, current collectors, electrolyte/separator, and packaging has to be redesigned. This requires a fundamental paradigm change in battery research, moving away from exclusively addressing the electrochemical aspects toward an interdisciplinary approach involving chemists, materials scientists, and engineers. This Outlook provides an overview of the different activities in the field of flexible, transient, and transparent batteries with a focus on the challenges that have to be faced toward the development of such multifunctional energy storage devices.

Nanoparticle-Based Electrodes with High Charge Transfer Efficiency through Ligand Exchange Layer-by-Layer Assembly

Organic-ligand-based solution processes of metal and transition metal oxide (TMO) nanoparticles (NPs) have been widely studied for the preparation of electrode materials with desired electrical and electrochemical properties for various energy devices. However, the ligands adsorbed on NPs have a significant effect on the intrinsic properties of materials, thus influencing the performance of bulk electrodes assembled by NPs for energy devices. To resolve these critical drawbacks, numerous approaches have focused on developing unique surface chemistry that can exchange bulky ligands with small ligands or remove bulky ligands from NPs after NP deposition. In particular, recent studies have reported that the ligand-exchange-induced layer-by-layer (LE-LbL) assembly of NPs enables controlled assembly of NPs with the desired interparticle distance, and interfaces, dramatically improving the electrical/electrochemical performance of electrodes. This emerging approach also demonstrates that efficient surface ligand engineering can exploit the unique electrochemical properties of individual NPs and maximize the electrochemical performance of the resultant NP-assembled electrodes through improved charge transfer efficiency. This report focuses on how LE-LbL assembly can be effectively applied to NP-based energy storage/conversion electrodes. First, the basic principles of the LE-LbL approach are introduced and then recent progress on NP-based energy electrodes prepared via the LE-LbL approach is reviewed.

Intercalation and flexibility chemistries of soft layered materials

Layered materials, alternate stackings of two or more components, are found in a wide range of scales. Chemists can design and synthesize layered structures containing functional units. The soft-type layered materials exhibit characteristic dynamic functions originating from two-dimensional (2D) anisotropy and structure flexibility. This feature article focuses on "intercalation" and "flexibility" as two new perspectives for designing soft layered materials. Intercalation of guests is a characteristic approach for design of layered structures. Flexibility is an important factor to control the dynamic functions of the layered structures. As a model case, the intercalation-induced tunable stimuli-responsive color-change properties of layered polydiacetylene (PDA) are introduced to study the impact of the intercalation and flexibility on the dynamic functions. Recently, layered materials have drastically expanded the research area from conventional rigid inorganic compounds to new self-assembled nanostructures consisting of organic components, such as polymers, metal-organic frameworks, and covalent-organic frameworks. These new layered architectures have potentials for exhibiting dynamic functions originating from the structure flexibility beyond the static properties originating from classical intercalation and host-guest chemistries. Therefore, intercalation and flexibility chemistries of soft layered materials are regarded as new perspectives for design of advanced dynamic functional materials.

Supramolecular Chiral Nanoarchitectonics

Exploration of molecular functions and material properties based on the control of chirality would be a scientifically elegant approach. Here, the fabrication and function of chiral-featured materials from both chiral and achiral components using a supramolecular nanoarchitectonics concept are discussed. The contents are classified in to three topics: i) chiral nanoarchitectonics of rather general molecular assemblies; ii) chiral nanoarchitectonics of metal-organic frameworks (MOFs); iii) chiral nanoarchitectonics in liquid crystals. MOF structures are based on nanoscopically well-defined coordinations, while mesoscopic orientations of liquid-crystalline phases are often flexibly altered. Discussion on the effects and features in these representative materials systems with totally different natures reveals the universal importance of supramolecular chiral nanoarchitectonics. Amplification of chiral molecular information from molecules to materials-level structures and the creation of chirality from achiral components upon temporal statistic fluctuations are universal, regardless of the nature of the assemblies. These features are thus surely advantageous characteristics for a wide range of applications.

Nanoarchitectonics beyond Self-Assembly: Challenges to Create Bio-Like Hierarchic Organization

Incorporation of non-equilibrium actions in the sequence of self-assembly processes would be an effective means to establish bio-like high functionality hierarchical assemblies. As a novel methodology beyond self-assembly, nanoarchitectonics, which has as its aim the fabrication of functional materials systems from nanoscopic units through the methodological fusion of nanotechnology with other scientific disciplines including organic synthesis, supramolecular chemistry, microfabrication, and bio-process, has been applied to this strategy. The application of non-equilibrium factors to conventional self-assembly processes is discussed on the basis of examples of directed assembly, Langmuir-Blodgett assembly, and layer-by-layer assembly. In particular, examples of the fabrication of hierarchical functional structures using bio-active components such as proteins or by the combination of bio-components and two-dimensional nanomaterials, are described. Methodologies described in this review article highlight possible approaches using the nanoarchitectonics concept beyond self-assembly for creation of bio-like higher functionalities and hierarchical structural organization.

Don't Forget Langmuir-Blodgett Films 2020: Interfacial Nanoarchitectonics with Molecules, Materials, and Living Objects

Designing interfacial structures with nanoscale (or molecular) components is one of the important tasks in the nanoarchitectonics concept. In particular, the Langmuir-Blodgett (LB) method can become a promising and powerful strategy in interfacial nanoarchitectonics. From this viewpoint, the status of LB films in 2020 will be discussed in this feature article. After one section on the basics of interfacial nanoarchitectonics with the LB technique, various recent research examples of LB films are introduced according to classifications of (i) growing research, (ii) emerging research, and (iii) future research. In recent LB research, various materials other than traditional lipids and typical amphiphiles can be used as film components of the LB techniques. Two-dimensional materials, supramolecular structures such as metal organic frameworks, and biomaterials such as DNA origami pieces are capable of working as functional components in the LB assemblies. Possible working areas of the LB methods would cover emerging demands, including energy, environmental, and biomedical applications with a wide range of functional materials. In addition, forefront research such as molecular manipulation and cell fate control is conducted in LB-related interfacial science. The LB technique is a traditional and well-develop methodology for molecular films with a ca. 100 year history. However, there is plenty of room at the interfaces, as shown in LB research examples described in this feature article. It is hoped that the continuous development of the science and technology of the LB method make this technique an unforgettable methodology.

From Molecular Reconstruction of Mesoscopic Functional Conductive Silk Fibrous Materials to Remote Respiration Monitoring

Turning insulating silk fibroin materials into conductive ones turns out to be the essential step toward achieving active silk flexible electronics. This work aims to acquire electrically conductive biocompatible fibers of regenerated Bombyx mori silk fibroin (SF) materials based on carbon nanotubes (CNTs) templated nucleation reconstruction of silk fibroin networks. The electronical conductivity of the reconstructed mesoscopic functional fibers can be tuned by the density of the incorporated CNTs. It follows that the hybrid fibers experience an abrupt increase in conductivity when exceeding the percolation threshold of CNTs >35 wt%, which leads to the highest conductivity of 638.9 S m^-1 among organic-carbon-based hybrid fibers, and 8 times higher than the best available materials of the similar types. In addition, the silk-CNT mesoscopic hybrid materials achieve some new functionalities, i.e., humidity-responsive conductivity, which is attributed to the coupling of the humidity inducing cyclic contraction of SFs and the conductivity of CNTs. The silk-CNT materials, as a type of biocompatible electronic functional fibrous material for pressure and electric response humidity sensing, are further fabricated into a smart facial mask to implement respiration condition monitoring for remote diagnosis and medication.

Identification of Metal-Binding Peptides and Their Conjugation onto Nanoparticles of Superparamagnetic Iron Oxides and Liposomes

Metallic materials are used for clinical medical devices such as vascular stents and coils to treat both ischemic and hemorrhagic vascular diseases. An antiplatelet drug is required to avoid thromboembolic complication until metallic surface is covered with a neo-endothelial cell layer. It is important to identify endothelial cell coverage on the metallic surface. However, it is difficult since there are no selective ligands. Here, we used the phage display method to identify peptide ligands that had high affinity for the metallic surface of Ni-Ti stents, Pt-W coils, and Co-Cr stents. The binding assay using fluorescence labeling revealed that several synthetic peptides could bind onto those surfaces. We also chose some oligopeptides for the conjugation onto superparamagnetic iron oxide (SPIO) nanoparticles and liposome-encapsulating SPIO nanoparticles and studied their ability to bind to the stent and coils. By SEM and fluorophotometry, we found that those modified SPIOs and liposomes were selectively bound onto those surfaces. In addition, both treated stents and coils could be detected by magnetic resonance imaging due to the magnetic artifact through the SPIOs and liposomes that were immobilized onto the surface. Thus, we identified metal-binding peptides which may enable to stop antiplatelet therapy after vascular stenting or coiling.

Mechanical Tolerance of Cascade Bioreactions via Adaptive Curvature Engineering for Epidermal Bioelectronics

Epidermal bioelectronics that can monitor human health status non-invasively and in real time are core to wearable healthcare equipment. Achieving mechanically tolerant surface bioreactions that convert biochemical information to detectable signals is crucial for obtaining high sensing fidelity. In this work, by combining simulations and experiments, a typical epidermal biosensor system is investigated based on a redox enzyme cascade reaction (RECR) comprising glucose oxidase/lactate oxidase enzymes and Prussian blue nanoparticles. Simulations reveal that strain-induced change in surface reactant flux is the key to the performance drop in traditional flat bioelectrodes. In contrast, wavy bioelectrodes capable of curvature adaptation maintain the reactant flux under strain, which preserves sensing fidelity. This rationale is experimentally proven by bioelectrodes with flat/wavy geometry under both static strain and dynamic stretching. When exposed to 50% strain, the signal fluctuations for wavy bioelectrodes are only 7.0% (4.9%) in detecting glucose (lactate), which are significantly lower than the 40.3% (51.8%) in flat bioelectrodes. Based on this wavy bioelectrode, a stable human epidermal metabolite biosensor insensitive to human gestures is further demonstrated. This mechanically tolerant biosensor based on adaptive curvature engineering provides a reliable bio/chemical-information monitoring platform for soft healthcare bioelectronics.

2D Nanoarchitectonics: Soft Interfacial Media as Playgrounds for Microobjects, Molecular Machines, and Living Cells

Soft and flexible two-dimensional (2D) systems, such as liquid interfaces, would have much more potentials in dynamic regulation on nano-macro connected functions. In this Minireview article, we focus especially on dynamic motional functions at liquid dynamic interfaces as 2D material systems. Several recent examples are selected to be explained for overviewing features and importance of dynamic soft interfaces in a wide range of action systems. The exemplified research systems are mainly classified into three categories: (i) control of microobjects with motional regulations; (ii) control of molecular machines with functions of target discrimination and optical outputs; (iii) control of living cells including molecular machine functions at cell membranes and cell/biomolecular behaviors at liquid interface. Sciences on soft 2D media with motional freedom and their nanoarchitectonics constructions will have increased importance in future technology in addition to popular rigid solid 2D materials.

Nanoarchitectonics of Nanoporous Carbon Materials in Supercapacitors Applications

High surface area and large pore volume carbon materials having hierarchical nanoporous structure are required in high performance supercapacitors. Such nanoporous carbon materials can be fabricated from organic precursors with high carbon content, such as synthetic biomass or agricultural wastes containing cellulose, hemicellulose, and lignin. Using recently developed unique concept of materials nanoarchitectonics, high performance porous carbons with controllable surface area, pore size distribution, and hierarchy in nanoporous structure can be fabricated. In this review, we will overview the recent trends and advancements on the synthetic methods for the production of hierarchical porous carbons with one- to three-dimensional network structure with superior performance in supercapacitors applications. We highlight the promising scope of accessing nanoporous graphitic carbon materials from: (i) direct conversion of single crystalline self-assembled fullerene nanomaterials and metal organic frameworks, (ii) hard- and soft-templating routes, and (iii) the direct carbonization and/or activation of biomass or agricultural wastes as non-templating routes. We discuss the appealing points of the different synthetic carbon sources and natural precursor raw-materials derived nanoporous carbon materials in supercapacitors applications.

Nanoarchitectonics from Atom to Life

Functional materials with rational organization cannot be directly created only by nanotechnology-related top-down approaches. For this purpose, a novel research paradigm next to nanotechnology has to be established to create functional materials on the basis of deep nanotechnology knowledge. This task can be assigned to an emerging concept, nanoarchitectonics. In the nanoarchitectonics approaches, functional materials were architected through combination of atom/molecular manipulation, organic chemical synthesis, self-assembly and related spontaneous processes, field-applied assembly, micro/nano fabrications, and bio-related processes. In this short review article, nanoarchitectonics-related approaches on materials fabrications and functions are exemplified from atom-scale to living creature level. Based on their features, unsolved problems for future developments of the nanoarchitectonics concept are finally discussed.

Cyber-Physiochemical Interfaces

Living things rely on various physical, chemical, and biological interfaces, e.g., somatosensation, olfactory/gustatory perception, and nervous system response. They help organisms to perceive the world, adapt to their surroundings, and maintain internal and external balance. Interfacial information exchanges are complicated but efficient, delicate but precise, and multimodal but unisonous, which has driven researchers to study the science of such interfaces and develop techniques with potential applications in health monitoring, smart robotics, future wearable devices, and cyber physical/human systems. To understand better the issues in these interfaces, a cyber-physiochemical interface (CPI) that is capable of extracting biophysical and biochemical signals, and closely relating them to electronic, communication, and computing technology, to provide the core for aforementioned applications, is proposed. The scientific and technical progress in CPI is summarized, and the challenges to and strategies for building stable interfaces, including materials, sensor development, system integration, and data processing techniques are discussed. It is hoped that this will result in an unprecedented multi-disciplinary network of scientific collaboration in CPI to explore much uncharted territory for progress, providing technical inspiration-to the development of the next-generation personal healthcare technology, smart sports-technology, adaptive prosthetics and augmentation of human capability, etc.

Water-Processable, Stretchable, Self-Healable, Thermally Stable, and Transparent Ionic Conductors for Actuators and Sensors

For emerging biocompatible, wearable, and stretchable epidermal electronic devices, it is essential to realize novel stretchable conductors with the attributes of transparency, low-cost and nontoxic components, green-solvent processbility, self-healing, and thermal stabililty. Although conducting materials-rubber composites, ionic hydrogels, organogels have been developed, no stretchable material system that meets all the outlined requirements has been reported. Here, a series of P(SPMA-r-MMA) polymers with different ratios of ionic side chains is designed and synthesized, and it is demonstrated that the resulting stretchable ionic conductors with glycerol are transparent, water processable, self-healable, and thermally stable due to the chemically linked ionic side chain, satisfying all of the aforementioned requirements. Among the series of polymer gels, the P(SPMA_0.75 -r-MMA_0.25 ) gel shows optimum conductivity (6.7 × 10^-4 S cm^-1 ), stretchability (2636% of break at elongation), and self-healing (98.3% in 3 h) properties. Accordingly, the transparent and self-healable P(SPMA_0.75 -r-MMA_0.25 ) gels are used to realize thermally robust actuators up to 100 °C and deformable and self-healable thermal sensors.

Building memory devices from biocomposite electronic materials

Natural biomaterials are potential candidates for the next generation of green electronics due to their biocompatibility and biodegradability. On the other hand, the application of biocomposite systems in information storage, photoelectrochemical sensing, and biomedicine has further promoted the progress of environmentally benign bioelectronics. Here, we mainly review recent progress in the development of biocomposites in data storage, focusing on the application of biocomposites in resistive random-access memory (RRAM) and field effect transistors (FET) with their device structure, working mechanism, flexibility, transient characteristics. Specifically, we discuss the application of biocomposite-based non-volatile memories for simulating biological synapse. Finally, the application prospect and development potential of biocomposites are presented.

Halloysite Nanoclay/Biopolymers Composite Materials in Tissue Engineering

Biocompatible materials for the fabrication of tissue substitutes are crucially important in the advancement of modern medicinal biotechnology. These materials, to serve their function, should be similar in physical, chemical, biological, and structural properties to native tissues which they are aimed to mimic. The porosity of artificial scaffolds is essential for normal nutrient transmission to cells, gas diffusion, and cell attachment and proliferation. Nanoscale inorganic additives and dopants are widely used to improve the functional properties of the polymer materials for tissue engineering. Among these inorganic dopants, halloysite nanotubes are arguably the most perspective candidates because of their biocompatibility and functional properties allowing to enhance significantly the mechanical and chemical stability of tissue engineering scaffolds. Here, this vibrant field of biotechnology for regenerative medicine is overviewed.

Immobilization of Polyiodide Redox Species in Porous Carbon for Battery-Like Electrodes in Eco-Friendly Hybrid Electrochemical Capacitors

Hybrid electrochemical capacitors have emerged as attractive energy storage option, which perfectly fill the gap between electric double-layer capacitors (EDLCs) and batteries, combining in one device the high power of the former and the high energy of the latter. We show that the charging characteristics of the positive carbon electrode are transformed to behave like a battery operating at nearly constant potential after it is polarized in aqueous iodide electrolyte (1 mol L⁻¹ NaI). Thermogravimetric analysis of the positive carbon electrode confirms the decomposition of iodides trapped inside the carbon pores in a wide temperature range from 190 °C to 425 °C, while Raman spectra of the positive electrode show characteristic peaks of I₃⁻ and I₅⁻ at 110 and 160 cm⁻¹, respectively. After entrapment of polyiodides in the carbon pores by polarization in 1 mol L⁻¹ NaI, the positive electrode retains the battery-like behavior in another cell, where it is coupled with a carbon-based negative electrode in aqueous NaNO₃ electrolyte without any redox species. This new cell (theiodide-ion capacitor) demonstrates the charging characteristics of a hybrid capacitor with capacitance values comparable to the one using 1 mol L⁻¹ NaI. The constant capacitance profile of the new hybrid cell in aqueous NaNO₃ for 5000 galvanostatic charge/discharge cycles at 0.5 A g⁻¹ shows that iodide species are confined to the positive battery-like electrode exhibiting negligible potential decay during self-discharge tests, and their shuttling to the negative electrode is prevented in this system.

Highly Stable and Stretchable Conductive Films through Thermal-Radiation-Assisted Metal Encapsulation

Stretchable conductors are the basic units of advanced flexible electronic devices, such as skin-like sensors, stretchable batteries and soft actuators. Current fabrication strategies are mainly focused on the stretchability of the conductor with less emphasis on the huge mismatch of the conductive material and polymeric substrate, which results in stability issues during long-term use. Thermal-radiation-assisted metal encapsulation is reported to construct an interlocking layer between polydimethylsiloxane (PDMS) and gold by employing a semipolymerized PDMS substrate to encapsulate the gold clusters/atoms during thermal deposition. The stability of the stretchable conductor is significantly enhanced based on the interlocking effect of metal and polymer, with high interfacial adhesion (>2 MPa) and cyclic stability (>10 000 cycles). Also, the conductor exhibits superior properties such as high stretchability (>130%) and large active surface area (>5:1 effective surface area/geometrical area). It is noted that this method can be easily used to fabricate such a stretchable conductor in a wafer-scale format through a one-step process. As a proof of concept, both long-term implantation in an animal model to monitor intramuscular electric signals and on human skin for detection of biosignals are demonstrated. This design approach brings about a new perspective on the exploration of stretchable conductors for biomedical applications.

Giant Poisson's Effect for Wrinkle-Free Stretchable Transparent Electrodes

The next generation of flexible electronics will require highly stretchable and transparent electrodes, many of which consist of a relatively stiff metal network (or carbon materials) and an underlying soft substrate. Typically, such a stiff-soft bilayer suffers from wrinkling or folding when subjected to strains, causing high surface roughness and seriously deteriorated optical transparency. In this work, a network with a giant effective Poisson's ratio on a soft substrate is found to be under biaxial tension upon deformation, and thus does not wrinkle or fold, but maintains smooth surfaces and high transparency. Soft tactile sensors employing such network electrodes exhibit high transparency and low fatigue over many stretching cycles. Such a giant Poisson's ratio has the same effect in other systems. This work offers a new understanding of surface instabilities and a general strategy to prevent them not only in flexible electronics, but also in other materials and mechanical structures that require flat surfaces.

Layer-by-Layer Assembly: Recent Progress from Layered Assemblies to Layered Nanoarchitectonics

As an emerging concept for the development of new materials with nanoscale features, nanoarchitectonics has received significant recent attention. Among the various approaches that have been developed in this area, the fixed-direction construction of functional materials, such as layered fabrication, offers a helpful starting point to demonstrate the huge potential of nanoarchitectonics. In particular, the combination of nanoarchitectonics with layer-by-layer (LbL) assembly and a large degree of freedom in component availability and technical applicability would offer significant benefits to the fabrication of functional materials. In this Minireview, recent progress in LbL assembly is briefly summarized. After introducing the basics of LbL assembly, recent advances in LbL research are discussed, categorized according to physical, chemical, and biological innovations, along with the fabrication of hierarchical structures. Examples of LbL assemblies with graphene oxide are also described to demonstrate the broad applicability of LbL assembly, even with a fixed material.