Breathable Nanowood Biofilms as Guiding Layer for Green On‐Skin Electronics

Thin‐film electronics are urged to be directly laminated onto human skin for reliable, sensitive biosensing together with feedback transdermal therapy, their self‐power supply using the thermoelectric and moisture‐induced‐electric effects also has gained great attention (skin and on‐skin electronics (On‐skinE) themselves are energy storehouses). However, “thin‐film” On‐skinE 1) cannot install “bulky” heatsinks or sweat transport channels, but the output power of thermoelectric generator and moisture‐induced‐electric generator relies on the temperature difference (?T ) across generator and the ambient humidity (AH), respectively; 2) lack a routing and accumulation of sweat for biosensing, lack targeted delivery of drugs for precise transdermal therapy; and 3) need insulation between the heat‐generating unit and heat‐sensitive unit. Here, two breathable nanowood biofilms are demonstrated, which can help insulate between units and guide the heat and sweat to another in‐plane direction. The transparent biofilms achieve record‐high transport_///transport_⊥ (//: along cellulose nanofiber alignment direction, ⊥: perpendicular direction) of heat (925%) and sweat (338%), winning applications emphasizing on ?T/AH‐dependent output power and “reliable” biosensing. The porous biofilms are competent in applications where “sensitive” biosensing (transporting_// sweat up to 11.25 mm s^?1 at the 1st second), “insulating” between units, and “targeted” delivery of saline‐soluble drugs are of uppermost priority.     

Triple Acceptors in a Polymeric Architecture for Balanced Ambipolar Transistors and High‐Gain Inverters

The exploration of novel molecular architectures is crucial for the design of high‐performance ambipolar polymer semiconductors. Here, a “triple‐acceptors architecture” strategy to design the ambipolar polymer DPP‐2T‐DPP‐TBT is introduced. The utilization of this architecture enables DPP‐2T‐DPP‐TBT to achieve deep‐lying highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels of ?5.38/?4.19 eV, and strong intermolecular interactions, which are favorable for hole/electron injection and intermolecular hopping through π‐stacking. All these factors result in excellent ambipolar transport characteristics and promising applications in complementary‐like circuits for DPP‐2T‐DPP‐TBT under ambient conditions with high hole/electron mobilities and a gain value of up to 3.01/3.84 cm² V^?1 s^?1 and 171, respectively, which are among the best performances in ambipolar polymer organic thin‐film transistors and associated complementary‐like circuits, especially in top‐gate device configuration with low‐cost glass as substrates. These results demonstrate that the “triple‐acceptors architecture” strategy is an effective way for designing high‐performance ambipolar polymer semiconductors.     

Moulded pulp products manufacturing with thermoforming

For an effective optimization of pulp thermoforming and of the moulded pulp products manufactured by this process, a full understanding of the process physics combined with full knowledge of the pressing equipment is necessary. For this reason, in this Addendum, we clarify how the process parameters “Holding time,” “Vacuum time,” “Cycle time,” and “Temperature” were interpreted and subsequently defined for the analysis of the process and product‐related outputs of the thermoforming experiments.     

Thermally Driven Transport and Relaxation Switching Self‐Powered Electromagnetic Energy Conversion

Electromagnetic energy radiation is becoming a “health‐killer” of living bodies, especially around industrial transformer substation and electricity pylon. Harvesting, converting, and storing waste energy for recycling are considered the ideal ways to control electromagnetic radiation. However, heat‐generation and temperature‐rising with performance degradation remain big problems. Herein, graphene‐silica xerogel is dissected hierarchically from functions to “genes,” thermally driven relaxation and charge transport, experimentally and theoretically, demonstrating a competitive synergy on energy conversion. A generic approach of “material genes sequencing” is proposed, tactfully transforming the negative effects of heat energy to superiority for switching self‐powered and self‐circulated electromagnetic devices, beneficial for waste energy harvesting, conversion, and storage. Graphene networks with “well‐sequencing genes” (w = P_c/P_p > 0.2) can serve as nanogenerators, thermally promoting electromagnetic wave absorption by 250%, with broadened bandwidth covering the whole investigated frequency. This finding of nonionic energy conversion opens up an unexpected horizon for converting, storing, and reusing waste electromagnetic energy, providing the most promising way for governing electromagnetic pollution with self‐powered and self‐circulated electromagnetic devices.     

Single‐Layer Ternary Chalcogenide Nanosheet as a Fluorescence‐Based “Capture‐Release” Biomolecular Nanosensor

The novel application of two‐dimensional (2D) single‐layer ternary chalcogenide nanosheets as “capture‐release” fluorescence‐based biomolecular nanosensors is demonstrated. Fluorescently labeled biomolecular probe is first captured by the ultrathin Ta₂NiS₅ nanosheets and then released upon adding analyte containing a target biomolecule due to the higher probe‐target affinity. Here, the authors use a nucleic acid probe for the model target biomolecule Plasmodium lactate dehydrogenase, which is an important malarial biomarker. The ultrathin Ta₂NiS₅ nanosheet serves as a highly efficient fluorescence quencher and the nanosensor developed from the nanosheet is highly sensitive and specific toward the target biomolecule. Apart from the specificity toward the target biomolecule in homogeneous solutions, the developed nanosensor is capable of detecting and differentiating the target in heterogeneous solutions consisting of either a mixture of biomolecules or serum, with exceptional specificity. The simplicity of the “capture‐release” method, by eliminating the need for preincubation of the probe with the test sample, may facilitate further development of portable and rapid biosensors. The authors anticipate that this ternary chalcogenide nanosheet‐based biomolecular nanosensor will be useful for the rapid detection and differentiation of a wide range of chemical and biological species.     

Early Experiences in Cross‐Disciplinary Education in Biomedical Technology Innovation at Stanford University*

This paper describes two new educational programs at Stanford that address some of the unique issues in teaching medical technology innovation and design. The first is a team‐based medical device design and prototyping course that is based on clinical immersion and “hands‐on” device prototyping. Medical device innovation at Stanford is further encouraged by means of a series of university‐wide competitions, called Invention Challenges, to invent solutions to defined clinical problems with the potential for real‐world impact.     

Absorption Enhancement in “Giant” Core/Alloyed‐Shell Quantum Dots for Luminescent Solar Concentrator

Luminescent solar concentrators (LSCs) can potentially reduce the cost of solar cells by decreasing the photoactive area of the device and boosting the photoconversion efficiency (PCE). This study demonstrates the application of “giant” CdSe/Cd_xPb_1–xS core/shell quantum dots (QDs) as light harvesters in high performance LSCs with over 1.15% PCE. Pb addition is critical to maximize PCE. First, this study synthesizes “giant” CdSe/Cd_xPb_1–xS QDs with high quantum yield (40%), narrow size distribution (<10%), and stable photoluminescence in a wide temperature range (100–300 K). Subsequently these thick alloyed‐shell QDs are embedded in a polymer matrix, resulting in a highly transparent composite with absorption spectrum covering the range 300–600 nm, and are applied as active material for prototype LSCs. The latter exhibits a 15% enhancement in efficiency with respect to 1% PCE of the pure‐CdS‐shelled QDs. This study attributes this increase to the contribution of Pb doping. The results demonstrate a straightforward approach to enhance light absorption in “giant” QDs by metal doping, indicating a promising route to broaden the absorption spectrum and increase the efficiency of LSCs.     

Molecular Switch Controlled by Pulsed Bias Voltages

Recent experiments have shown that the current–voltage characteristics (I–V) of BPDN‐DT (bipyridyl‐dinitro oligophenylene‐ethynylene dithiol) can be switched in a very controlled manner between “on” and “off” traces by applying a pulse in a bias voltage, V_bias. Here, the polaron formation energies are calculated to check a frequently held belief, namely, that the polaron formation can explain the observed bistability. These results are not consistent with such a mechanism. Instead, a conformational reorientation is proposed. The molecule carries an intrinsic dipole moment, which couples to V_bias. Ramping V_bias exerts a force on the dipole that can reorient (“rotate”) the molecule from the ground state (“off”) into a metastable configuration (“on”) and back. By elaborated electronic structure calculations, a specific path for this rotation is identified through the molecule's conformational phase space. It is shown that this path has sufficiently high barriers to inhibit thermal instability but that the molecule can still be switched in the voltage range of the junction stability. The theoretical I–Vs qualitatively reproduce the key experimental observations. A proposal for the experimental verification of the alternative mechanism of conductance switching is presented.     

Simplicity as a Route to Impact in Materials Research

Materials scientists and engineers desire to have an impact. In this Progress Report we postulate a close correlation between impact – whether academic, technological, or scientific – and simple solutions, here defined as solutions that are inexpensive, reliable, predictable, highly performing, “stackable” (i.e., they can be combined and compounded with little increase in complexity), and “hackable” (i.e., they can be easily modified and optimized). In light of examples and our own experience, we propose how impact can be pursued systematically in materials research through a simplicity‐driven approach to discovery‐driven or problem‐driven research.     

Methoden zur betriebsfesten Bauteilvorbemessung von innendruckbeaufschlagten Bauteilen aus hochfesten Eisengusswerkstoffen

In the present paper methods based on the related stress gradient χ* and the highly stressed material volume HBV_90% for the assessment of the structural durability of high‐strength ductile iron components are presented. Approximate solutions were formulated on the basis of extensive fatigue tests under constant amplitude loading using specimens from the alloys EN‐GJS‐500‐7, SiboDur 700‐10 and MADI. The estimated fatigue strengths were validated by tests with the so‐called “Pulsing Dummy Model Bodies”, samples with a bore intersection with an angle of 45° as critical area.     

Optically Rewritable Transparent Liquid Crystal Displays Enabled by Light‐Driven Chiral Fluorescent Molecular Switches

Functional soft materials exhibiting distinct functionalities in response to a specific stimulus are highly desirable towards the fabrication of advanced devices with superior dynamic performances. Herein, two novel light‐driven chiral fluorescent molecular switches have been designed and synthesized that are able to exhibit unprecedented reversible Z/E photoisomerization behavior along with tunable fluorescence intensity in both isotropic and anisotropic media. Cholesteric liquid crystals fabricated using these new fluorescent molecular switches as chiral dopants exhibit reversible reflection color tuning spanning the visible and infrared region of the spectrum. Transparent display devices have been fabricated using both low chirality and high chirality cholesteric films that operate either exclusively in fluorescent mode or in both fluorescent and reflection mode, respectively. The dual mode display device employing short pitch cholesteric film is able to function on demand under all ambient light conditions including daylight and darkness with fast response and high resolution. Moreover, the proof‐of‐concept for a “remote‐writing board” using cholesteric films containing one of the light‐driven chiral fluorescent molecular switches with ease of fabrication and operation is disclosed herein. Such optically rewritable transparent display devices enabled by light‐driven chiral fluorescent molecular switches pave a new way for developing novel display technology under different lighting conditions.     

The “<Emphasis Type="Italic">Daphnia</Emphasis>” Lynx Mark I Suborbital Flight Experiment: Hardware Qualification at the Drop Tower Bremen

The Drop Tower Bremen, a ground-based facility enabling research under real microgravity conditions, is an excellent platform for testing new types of experimental hardware to ensure full performance when deployed in costly and rare flight opportunities such as suborbital flights. Here we describe the “Daphnia” experiment which will fly on XCOR Aerospace Lynx Mark I and our experience from the hardware tests with the catapult system at the drop tower. The aim of the “Daphnia” experiment is to obtain data on the biological performance of daphnids and predator-prey interactions in microgravity, which are important for the development of aquatic bioregenerative life support systems (BLSS). The experiment consists of two subunits: The first unit is dedicated to predator-prey interactions, where behavioural analysis should reveal if microgravity interfere with prey (Daphnia) detection or feeding and therefore may interrupt the trophic cascade. The functioning of such an artificial food web is indispensable for a long-lasting BLSS suitable for long-duration manned space missions or Earth-based explorations to extreme habitats. The second unit is designed to investigate the impact of microgravity on gene expression and the cytoskeleton in Daphnia. Next to data collection, the real microgravity conditions at the drop tower have helped to identify the weak points of the “Daphnia” experimental hardware and lead to further improvement. Hence, the drop tower is ideal for testing new experimental hardware which is indispensable before the implementation in suborbital flights.     

Wafer Scale Solventless Adhesive Bonding with iCVD Polyglycidylmethacrylate: Effects of Bonding Parameters on Adhesion Energies

Initiated chemical vapor deposition (iCVD) polyglycidylmethacrylate (PGMA) thin films are investigated as adhesives for wafer‐scale bonding of 300 mm silicon substrates and demonstrated to form highly uniform, void‐free bond interfaces. The effects of bonding temperature and pressure on critical adhesion energy (G_c) between iCVD PGMA and silicon are studied using the four‐point bend technique. G_c values can be varied over an order of magnitude (0.59–41.6 J m⁻²) by controlling the bonding temperature and the observed dependence is attributed to changes in the physical (diffusion) and chemical (crosslinking) properties of the film. Thermal degradation studies using spectroscopic ellipsometry reveal that the iCVD PGMA films can crosslink when annealed above 120 °C in air. Further, changes in polymer behavior associated with annealing temperature are demonstrated to influence the crack propagation interface between the bonded substrates. These findings demonstrate the feasibility of iCVD polymer films for both temporary “thermoplastic,” and permanent “thermoset” bonding with potential applications in 3D integrated circuit technologies.     

Engineering Bimetallic Ag–Cu Nanoalloys for Highly Efficient Oxygen Reduction Catalysts: A Guideline for Designing Ag‐Based Electrocatalysts with Activity Comparable to Pt/C‐20%

Development of highly active and stable Pt‐free oxygen reduction reaction catalysts from earth‐abundant elements remains a grand challenge for highly demanded metal–air batteries. Ag‐based alloys have many advantages over platinum group catalysts due to their low cost, high stability, and acceptable oxygen reduction reaction (ORR) performance in alkaline solutions. Nevertheless, compared to commercial Pt/C‐20%, their catalytic activity still cannot meet the demand of commercialization. In this study, a kind of catalysts screening strategy on Ag_x Cu_100?x nanoalloys is reported, containing the surface modification method, studies of activity enhancement mechanism, and applied research on zinc–air batteries. The results exhibit that the role of selective dealloying (DE) or galvanic displacement (GD) is limited by the “parting limitation”, and this “parting limitation” determines the surface topography, position of d‐band center, and ORR performance of Ag_x Cu_100?x alloys. The GD‐Ag₅₅Cu₄₅ and DE‐Ag₂₅Cu₇₅ catalysts alloys present excellent ORR performance that is comparable to Pt/C‐20%. The relationship between electronic perturbation and specific activity demonstrates that positive shift of the d‐band center (≈0.12 eV, relative to Ag) for GD‐Ag₅₅Cu₄₅ is beneficial for ORR, which is contrary to Pt‐based alloys (negative shift, ≈0.1 eV). Meanwhile, extensive electrochemical and electronic structure characterization indicates that the high work function of GD‐Ag₅₅Cu₄₅ (4.8 eV) is the reason behind their excellent durability for zinc–air batteries.     

15 Years of Small: Research Trends in Nanosafety

In the field of nano‐ and microscale science and technology, Small has become one of the worldwide leading journals since its initiation 15 years ago. Among all the topics covered in Small, “nanosafety” has received growing interest over the years, which accounts for a large proportion of the total publications of Small. Herein, inspired by its coming Special Issue “Rethinking Nanosafety,” a general bibliometric overview of the nanosafety studies that have been published in Small is presented. Using the data derived from the Web of Science Core Collection, the annual publication growth, most influential countries/institutions as well as the visualized collaborations between different countries and institutions based on CiteSpace software are presented. A special emphasis on the impact of the previous Special Issue from Small that is related to nanosafety research is given and the research trend from the most highly cited papers during last 15 years is analyzed. Lastly, future research directions are also proposed.     

Mineralization of Collagen‐Coated Electrospun Poly(lactide‐co‐glycolide) Nanofibrous Mesh to Enhance Growth and Differentiation of Osteoblasts and Bone Marrow Mesenchymal Stem Cells

To obtain the biomimetic scaffolding materials for bone tissue engineering, poly(lactide‐co‐glycolide) (PLGA) nanofibrous mesh (NFM) was mineralized in a 5× simulated body fluid (SBF) for different time after it was treated by air plasma for 15 min and subsequent collagen coating. The apatite particles were nucleated on the surface of individual nanofibers, gradually grew up, and finally covered the whole NFM surface. The mineral aggregates were mainly composed of tiny hydroxyapatite (HA) nanoparticles, whose content reached a constant value of 54 µg · cm^?2 after 9 days. The collagen coating and apatite deposition enhanced the NFM strength pronouncedly too. In vitro cell culture demonstrated that the non‐ or less mineralized NFMs were more beneficial of cell spreading and proliferation than those highly mineralized NFMs, but the latter ones could strongly promote secretion of alkaline phosphatase (ALP) by osteoblasts after cultured for 14 days. Moreover, the highly mineralized NFMs also could significantly up‐regulated ALP activity and calcium synthesis of bone marrow mesenchymal stem cells (BMSCs), demonstrating that these NFMs are more favorable of the osteoblast phenotype expression and osteogenic induction. Therefore, the biomimetic apatite deposited PLGA/collagen NFM could be a promising candidate scaffold for bone tissue engineering.     

Fatigue crack closure: A myth or a misconception?

In this paper, we have extended our previous study on fatigue crack closure to examine the phenomenon of crack opening displacement (COD) and its impact on the crack tip fields in both 2D and 3D specimen geometries using full‐field experimental measurements and integrated finite element modelling. Digital image correlation (DIC) and digital volume correlation (DVC) were used to measure the near‐tip material responses on the surfaces (DIC) and the interior (DVC) of the specimens. Materials with elastic‐plastic and large plastic characteristics were chosen for the study, where plasticity‐induced premature contact between the crack flanks is known to occur. Displacement maps around the cracks were obtained using DIC and DVC at selected load increments and were introduced as boundary conditions into the finite element (FE) models to obtain the “effective” crack driving force in terms of J‐integral, and the results were compared with those “nominal” from the standard FE analysis. Both visual observation and compliance curves were used to determine the “crack opening” levels; whilst the impacts of the crack opening on the crack driving force J and the normal strains ahead of the crack tip were evaluated in 2D and 3D. The results from the study indicate that, crack closure, although clearly identifiable in the compliance curves, does not appear to impact on global crack driving force, such as J‐integral, or strains ahead of the crack tip; hence, it may well be a misconception.     

Liberating N‐CNTs Confined Highly Dispersed Co?Nx Sites for Selective Hydrogenation of Quinolines

Selective hydrogenation of quinoline and its derivatives is an important means to produce corresponding 1,2,3,4‐tetrahydroquinolines for a wide spectrum of applications. A facile and efficient “laser irradiation in liquid” technique to liberate the inaccessible highly dispersed Co? N_x active sites confined inside N‐doped carbon nanotubes is demonstrated. The liberated Co? N_x sites possess generic catalytic activities toward selective hydrogenation of quinoline and its hydroxyl, methyl, and halogen substituted derivatives into corresponding 1,2,3,4‐tetrahydroquinolines with almost 100% conversion efficiency and selectivity. This laser irradiation treatment approach should be widely applicable to unlock the catalytic powers of inaccessible catalytic active sites confined by other materials.     

Zero Linear Compressibility in Nondense Borates with a “Lu‐Ban Stool”‐Like Structure

Discovering materials that exhibit zero linear compressibility (ZLC) behavior under hydrostatic pressure is extremely difficult. To date, only a handful of ZLC materials have been found, and almost all of them are ultrahard materials with densified structures. Here, to explore ZLC in nondense materials, a structural model analogous to the structure of the “Lu‐Ban stool,” a product of traditional Chinese woodworking invented 2500 years ago, is proposed. The application of this model to borates leads to the discovery of ZLC in AEB₂O₄ (AE = Ca and Sr) with the unique “Lu‐Ban stool”‐like structure, which can obtain a subtle mechanical balance between pressure‐induced expansion and contraction effects. Coupled with the very wide ultraviolet transparent windows, the ZLC behavior of AEB₂O₄ may result in some unique but important applications. The applications of the “Lu‐Ban stool” model open a new route for pursuing ZLC materials in nondense structural systems.     

Biological Metabolism Synthesis of Metal Oxides Nanorods from Bacteria as a Biofactory toward High‐Performance Lithium‐Ion Battery Anodes

Increasing awareness toward environmental remediation and renewable energy has led to a vigorous demand for exploring a win‐win strategy to realize the eco‐efficient conversion of pollutants (“trash”) into energy‐storage nanomaterials (“treasure”). Inspired by the biological metabolism of bacteria, Acidithiobacillus ferrooxidans (A. ferrooxidans) is successfully exploited as a promising eco‐friendly sustainable biofactory for the controllable fabrication of α‐Fe₂O₃ nanorods via the oxidation of soluble ferrous irons to insoluble ferric substances (Jarosite, KFe₃(SO₄)₂(OH)₆) and a facile subsequent heat treatment. It is demonstrated that the stable solid electrolyte interphase layers and marvelous cracks in situ formed in biometabolic α‐Fe₂O₃ nanorods play important roles that not only significantly enhance the structure stability but also facilitate electron and ion transfer. Consequently, these biometabolic α‐Fe₂O₃ nanorods deliver a superior stable capacity of 673.9 mAh g^?1 at 100 mA g^?1 over 200 cycles and a remarkable multi‐rate capability that observably prevails over the commercial counterpart. It is highly expected that such biological synthesis strategies can shed new light on an emerging field of research interconnecting biotechnology, energy technology, environmental technology, and nanotechnology.