Search

Abstract: Photocleavable polymers have attracted much attention in drug delivery, photopatterning, and controlling cell behavior. Photolysis is usually induced by UV light. However, UV light cannot penetrate deeply into biological tissue and may damage biological components. Therefore, conventional UV‐light‐cleavable polymers are problematic for deep‐tissue biomedical applications. In this feature article, red and near‐infrared light‐cleavable polymers are reviewed, and their potential applications are highlighted. The remaining challenges in the field of photocleavable polymers are discussed. [ABSTRACT FROM AUTHOR]

All-inorganic quasi two-dimensional (quasi-2D) or two/three-dimensional (2D/3D) mixed perovskites are still in their infancy, even though they are expected to inherit the advantages of quasi-2D perovskites and all-inorganic perovskites employed in solar cells, light-emitting diodes, and detectors. Herein, we studied a series of all inorganic 2D/3D halide perovskite materials, Csx+2Pbx+1(SCN)2(I/Br)3x+2. Different from common organic–inorganic hybrid quasi-2D perovskites exhibiting phase mixtures of different inorganic sheets, the Csx+2Pbx+1(SCN)2(I/Br)3x+2 (x = 1, 2, 3) phases only consist of 2D Cs2Pb(SCN)2(I/Br)2 and 3D CsPb(I/Br)3 perovskite phases (here x defines the ratio of 3D CsPb(I/Br)3 and 2D Cs2Pb(SCN)2(I/Br)2 perovskite phases). Based on the optimized morphology from the Pb(Ac)2 additive and hexadecyltrimethylammonium iodide (CTAI) passivation, the devices based on Csx+2Pbx+1(SCN)2I3x+2 (x = 3) achieve a PCE of 8.1%. [ABSTRACT FROM AUTHOR]

This paper describes a pneumatic valve controlled microdevice for performing mixing and reaction. This microdevice combined the degassed polydimethylsiloxane (PDMS) pumping method with a syringe-actuated valve system to control the dispensing and mixing of nanoliter solutions. The syringe was used to manually generate vacuum and to open the valves. Upon the opening of the valve, the microchamber was filled with the solution, which was driven by the external atmosphere through the degassed PDMS microchannel. With this microdevice, the enzymatic kinetics of alkaline phosphatase converting the fluorescein diphosphate was studied, and the Michaelis-Menten kinetics was analyzed. The microdevice has the advantages of simplicity and low cost in fabrication and operation. [ABSTRACT FROM AUTHOR]

Directed liquid metal (gallium‐based) manipulation and actuation are paramount for copious applications, including soft robotics, soft electronics, and targeted drug delivery. Although there are several strategies available to achieve mobility of liquid metals in a "wet" environment. Strategies to achieve and improve mobility of liquid metal droplets and puddles in a "dry" environment are scarce and rely on metallophobic surface design or liquid metal marbles. Here, high mobility of Galinstan is elucidated by combining metallophobic surface design and vertical vibrations. Vibration frequencies between 20 and 30 Hz are conducive to droplet movement and threshold inclination angles of 0.5° to 1° are observed upon actuation by these vibrations. The method itself is applicable for a wide range of droplet sizes (30 and 2000 µL) and very robust. The droplet movement typically comprises of periodic receding and advancing of the droplet and commences via a rolling mechanism rather than a gliding mechanism. Finally, it is shown that small (0.5 mm height) obstacles can be traversed by this method, indicating that it can be used in concert with other strategies, such as surface structuring strategies, which open up pathways for mobility and controlled actuation of liquid metal droplets in air. [ABSTRACT FROM AUTHOR]

[Display omitted] Healable electronic skins, an essential component for future soft robotics, implantable bioelectronics, and smart wearable systems, necessitate self-healable and pliable materials that exhibit functionality at intricate interfaces. Although a plethora of self-healable materials have been developed, the fabrication of highly conformal biocompatible functional materials on complex biological surfaces remains a formidable challenge. Inspired by regenerative properties of skin, we present the self-assembled transfer-printable liquid metal epidermis (SALME), which possesses autonomous self-healing capabilities at the oil–water interface. SALME comprises a layer of surfactant-grafted liquid metal nanodroplets that spontaneously assemble at the oil–water interface within a few seconds. This unique self-assembly property facilitates rapid restoration (<10 s) of SALME following mechanical damage. In addition to its self-healing ability, SALME exhibits excellent shear resistance and can be seamlessly transferred to arbitrary hydrophilic/hydrophobic curved surfaces. The transferred SALME effectively preserves submicron-scale surface textures on biological substrates, thus displaying tremendous potential for future epidermal bioelectronics. [ABSTRACT FROM AUTHOR]

Transient electronics with degradability or dissolvability on demand possess remarkable characteristics for wearable, bioelectronic, and implanted electronic devices. While synthetic materials have made significant progress in degradability and stretchability, they suffer from intrinsic limitations, including low degradation rates, poor mechanical compliance, and high production cost, which restrict the growth of transient electronic devices. Herein, a versatile fabrication strategy is presented for transient electronics that combine a resilient biopolymer substrate (gelatin biogels) with liquid metal (Galinstan). The circuits made from gelatin biogel‐based and liquid metal are mechanically resilient and durable, exhibiting good compliance with irregular and deformable surfaces, and thus can withstand long‐term exposure to dynamic deformation (about 60 000 cycles at a strain of 50%). More importantly, gelatin biogels are naturally derived and endowed with thermally reversible gelling, which enables on‐demand rapid dissolution and recycling of the materials. As a proof‐of‐concept, transient circuit‐based capacitive sensors, which can be degraded within 20 s, are fabricated for monitoring finger touching, morse code generation, and electrical touchpad. Such a strategy provides a guideline for designing transient electronics with a combination of biopolymer gels and liquid metal, and this approach is anticipated to find applications in human–machine interfaces and wearable devices. [ABSTRACT FROM AUTHOR]

Liquid metal (LM) droplet‐embedded polymer composites with exceptional thermal, electrical, and mechanical characteristics are attractive for applications in soft electronics and thermal management. Generally, a high volume fraction of LMs is required for desirable thermal and electrical properties, and thus recycling of LMs is favorable and cost effective. However, recycling LMs from composites remains a formidable challenge because the LM droplets are typically dispersed into a permanent covalently crosslinked polymer matrix. Here, a facile synthesis of LM‐polymer composites with high electrical conductivity (1800 S cm−1), high stretchability (1400% tensile strain), as well as degradability and recyclability is reported. The composite comprises a poly(2‐hydroxyethyl acrylate) hydrogel that is physically crosslinked by LM nanodroplets as a polymer matrix and either LM microdroplets or silver microflakes as a conductive filler. A postdrying process improves the mechanical performance of the composite while creating percolating pathways via the rearrangement of the conductive fillers, imparting high electrical conductivity to the composite. Moreover, the composites are readily degraded and dissolved in aqueous alkali solutions at room temperature thanks to the reactive nature of LM crosslinks, enabling high recycling efficiency of ≈80% and 95% for composites with LM microdroplets and silver microflakes as conductive fillers, respectively. [ABSTRACT FROM AUTHOR]

This study investigates the rheological properties of dual-network hydrogels based on acrylamide and sodium alginate under large deformations. The concentration of calcium ions affects the nonlinear behavior, and all gel samples exhibit strain hardening, shear thickening, and shear densification. The paper focuses on systematic variation of the alginate concentration—which serves as second network building blocks—and the Ca2+-concentration—which shows how strongly they are connected. The precursor solutions show a typical viscoelastic solution behavior depending on alginate content and pH. The gels are highly elastic solids with only relatively small viscoelastic components, i.e., their creep and creep recovery behavior are indicative of the solid state after only a very short time while the linear viscoelastic phase angles are very small. The onset of the nonlinear regime decreases significantly when closing the second network (alginate) upon adding Ca2+, while at the same time the nonlinearity parameters (Q0, I3/I1, S, T, e3/e1, and v3/v1) increase significantly. Further, the tensile properties are significantly improved by closing the alginate network by Ca2+ at intermediate concentrations. [ABSTRACT FROM AUTHOR]

The emergent transient electronics that can be destroyed or degraded harmlessly under an environmental stimulus are attracting extensive attentions toward eco‐friendly electronic devices and confidential communication applications. However, currently available transient electronics are limited by the poor recyclability of components, which fails to meet the ever‐increasing demands of advanced electronic devices. Here, this work reports a fully recyclable transient electronic device based on a multi‐layered architecture, comprising a liquid metal (LM) as the conductor and a NaOH solution‐embedded paraffin composite (NPC) as the degradation agent. Upon thermally triggered by the bottom heater, the middle‐layer LM circuit and the top NPC layer melt, releasing the aqueous alkali to destroy the circuit at a quick transient rate (46 ± 4 s). Afterward, both the free LM and paraffin are recycled at extremely high efficiencies, that is, 98% for LM owing to the self‐aggregation and fluidic nature, 95% for paraffin arising from the low melting point and good recoverability. The successful integration of transience and recycling abilities dramatically improves the feasibility of transient electronics in real applications, as further demonstrated in a radio‐frequency transmission device and a remote destructible memristor, which hold great promises for confidential data storage devices and next‐generation electronics. [ABSTRACT FROM AUTHOR]

Review: 74 refs. [ABSTRACT FROM AUTHOR]

A series of ester‐ether copolymers were obtained via the reaction between α,ω‐dihydroxyl poly(ϵ‐caprolactone) (PCL) and ethylene oxide (EO) or monosubstituted epoxides catalyzed by strong phosphazene bases. The two types of monomeric units were distributed in highly random manners due to the concurrence of epoxide ring‐opening and fast transesterification reactions. The substituent of epoxide showed an interesting bidirectional effect on the enzymatic degradability of the copolymer. Compared with PCL, copolymers derived from EO exhibited enhanced hydrophilicity and decreased crystallinity which then resulted in higher degradability. For the copolymers derived from propylene oxide and 1,2‐butylene oxide, the hydrophobic alkyl pendant groups also allowed lower crystallinity of the copolymers thus higher degradation rates. However, further enlarging the pendant groups by using styrene oxide or 2‐ethylhexyl glycidyl ether caused a decrease in the degradation rate, which might be ascribed to the higher bulkiness hindering the contact of ester groups with lipase. [ABSTRACT FROM AUTHOR]

Liquid metals are a class of materials with a millennia‐long history, albeit until 200 years ago, mostly centered on mercury‐based applications. The knowledge of mercury's toxicity and the discovery of it's bioaccumulation and biomagnification in the late 20th century resulted in phasing out mercury for copious application. Lead‐based, bismuth‐based, and sodium‐based technology has partially replaced mercury, but due to toxicity or reactivity issues, replacements for lead and sodium are sought. The discovery of indium and, especially, gallium has allowed for the third generation of alloys with a melting point close to room temperature. This review gives a comprehensive overview of the technological developments of fusible and liquid metals, i. e. metals and alloys with melting points below ca. 250 °C, from the early days to current research and industrial application. Special emphasis is focused on important steppingstones and recent developments of gallium‐based alloys as well as how they could be used for future applications. [ABSTRACT FROM AUTHOR]

The booming field of wearable devices has nourished progress in developing multifunctional wearable energy sources that can withstand deformations while maintaining their electrochemical functions. Unlike energy storage systems such as rechargeable batteries and supercapacitors, wearable biofuel cells (w‐BFCs) generate green electricity from energy‐dense carbon‐neutral fuels via highly efficient bioelectrochemical reactions, delivering excellent biocompatibility, remarkable environmental sustainability, and exceptional capability of miniaturization. These desirable merits give w‐BFCs great potential in the field of wearable applications. Moreover, emerging studies of w‐BFCs in self‐powered biosensing, controlled drug delivery, and wound dressings have greatly expanded their possible fields of application. Recent progress and strategies to accomplish flexible and stretchable w‐BFCs are summarized here. Novel materials and configurations with tailored features that can be employed to fabricate w‐BFCs are elaborated and discussed. Current applications and near‐future applications of w‐BFCs in health‐monitoring and medical treatment fields are outlined. Furthermore, challenges and perspectives regarding this emerging field of materials science and engineering are also emphasized. [ABSTRACT FROM AUTHOR]

Liquid metals have aroused interest in the scientific communities of electronics, engineering and biomedicine. In particular, the stabilization of liquid metal nanodroplets by surfactants and macromolecules has been investigated in the past extensively. Herein, we investigate the change in interfacial tension of the liquid metal Galinstan in contact with aqueous electrolytes upon addition of surfactants in aqueous solutions. We show that is governed by the chemical environment, the structure of the electric double layer (EDL) and the surfactant charge. In most environments a critical micelle concentration (CMC) can be determined, the value of which is in favorable agreement with literature values. Furthermore, based on the selective adsorption of the surfactant, the structure of the EDL is predicted and discussed, and the adsorption of surfactants is employed to mitigate liquid metal droplet coalescence. In this regard, the data suggests that the packing parameter, change in IFT upon surfactant addition and charge density of EDL are the main contributors for liquid metal droplet stability. [ABSTRACT FROM AUTHOR]

Recently, numerous research studies have contributed to engineering hydrogels by soaking strategies to obtain designed properties, from mechanical strengthening to environmentally adapting. Hydrogels are three-dimensional hydrophilic polymer networks dispersed in water with widespread applications. However, most of the traditional hydrogels possess limited mechanical strength and poor temperature and environmental tolerance, which limits their applications. Due to their unique water-rich property, the physical and chemical properties of hydrogels can be post-engineered by facile soaking strategies. The soaking strategies can be divided into two categories: the first involves soaking salt solutions into the aqueous phase of the gel, and the second involves soaking in organic solvents to displace the water in the gel, forming organohydrogels. In this feature article, we aim to summarize the most recent progress in designing and engineering hydrogels using soaking strategies, including strengthening hydrogels with superior mechanical properties, and providing the hydrogels with environmentally adapting properties, such as anti-freezing and anti-dehydration. The first section summarizes some common design principles and fabrication methods to strengthen hydrogels by soaking, and then it introduces some successful applications of these soaking-induced tough hydrogels. In the second section, the soaking strategy to engineer hydrogels with environmentally adapting properties is discussed. In the end, a brief outlook is proposed based on current challenges and the pros and cons of the soaking strategy. [ABSTRACT FROM AUTHOR]

Outer membrane vesicles (OMVs) are produced by Gram-negative bacteria both in vitro and in vivo. OMVs are nano-sized spherical vehicles formed by lipid bilayer membranes and contain multiple parent bacteria-derived components. Based on the presence of bacterial antigens, pathogen-associated molecular patterns (PAMPs), adhesins, various proteins and the vesicle structure, OMVs have been developed for biomedical applications as bacterial vaccines, adjuvants, cancer immunotherapy agents, drug delivery vehicles, and anti-bacteria adhesion agents. In this review, we analyze the contributions of the structure and composition of OMVs to their applications, summarize the methods used to isolate and characterize OMVs, and highlight recent progress and future perspectives of OMVs in biomedical applications. Unlabelled Image • OMVs have been developed as bacterial vaccines, adjuvants, cancer immunotherapy agents, drug delivery vehicles, and anti-bacteria adhesion agents. • The advantages and potential problems of OMVs in biomedical applications are comprehensively discussed in the review. • The methods used to isolate and characterize OMVs are summarized in the review. • The contribution of OMVs components to their biomedical applications is analyzed in the review. [ABSTRACT FROM AUTHOR]

Graphical abstract PDMS sponge supported DMAP on polymer brushes can be used as highly efficient recyclable base catalyst and ligand for various organic transformations and provide much better catalytic activities and selectivities than free DMAP in water. Highlights • PDMS sponge DMAP has high catalytic activity and selectivity in water. • The polymer brush nano-structures on sponge can provide excellent reactive sites. • The catalyst's easy preparation by solid-phase synthetic strategy. • Recyclable catalyst and ligand, and easy to scale up by a flow reactor. • This hydrophobic PDMS sponge will be an excellent catalyst carrier in water. Abstract The successfully developed polydimethylsiloxane (PDMS, a stable hydrophobic polymer material) sponge supported DMAP can be used as base catalyst and ligand to facilitate a series of organic transformations with high efficiency and good reusability in water. This PDMS sponge DMAP can provide much better catalytic activities and selectivities than free DMAP in water. Through an easy-to-build continuous flow reactor, the PDMS sponge DMAP facilitated reactions can be facilely scaled up. This porous hydrophobic PDMS sponge material will be a promising carrier for the development of highly efficient recyclable catalysts in water. [ABSTRACT FROM AUTHOR]

Deposition of adherent and low friction nanocrystalline diamond films on cemented carbide cutting tools has been realized by application of a self-assembly seeding process with the help of lysine as stabilizing and directing agent. The colloidal stability of as-received detonated nanodiamond (DND) particles was enhanced by simply adding lysine into the nanodiamond seeding solution and adjusting the pH. Due to the two amine moieties it enhances the adsorption of oxidized nanodiamond on negatively charged cemented carbide substrate. The DND particle adsorption and adhesion of nanocrystalline diamond films on WC-Co substrate strongly depended on factors, such as concentration of lysine, pH of seeding solution and concentration of DND particles. The highest nucleation density of 6.5 × 10 10  cm −2 was achieved with optimal colloidal stability, which was 10–100 times higher than most earlier published results on WC-Co substrate. Moreover, nanocrystalline diamond thin films were deposited uniformly and densely on cutting inserts while the film adhesion was significantly improved. Compared to diamond films prepared without the addition of lysine, the friction coefficient was 3-times lower. Therefore, electrostatic induced adsorption of diamond nanoparticles can serve to increase tool lifetime and enhance surface quality of a workpiece. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly breathable, water-repellent and antibacterial face mask was developed. • The antibacterial layer inhibits the passage of bacteria-containing aerogel. • The mask can monitor the breath condition in wireless and real-time fashion. Face masks with multiple functionalities and exceptional durability have attracted increasing interests during the COVID-19 pandemic. How to integrate the antibacterial property, comfortability during long-time wearing, and breath monitoring capability together on a face mask is still challenging. Here we developed a kind of face mask that assembles the particles-free water-repellent fabric, antibacterial fabric, and hidden breath monitoring device together, resulting in the highly breathable, water-repellent, and antibacterial face mask with breath monitoring capability. Based on the rational design of the functional layers, the mask shows exceptional repellency to micro-fogs generated during breathing while maintaining high air permeability and inhibiting the passage of bacteria-containing aerogel. More importantly, the multi-functional mask can also monitor the breath condition in a wireless and real-time fashion, and collect the breath information for epidemiological analysis. The resultant mask paves the way to develop multi-functional breath-monitoring masks that can aid the prevention of the secondary transmission of bacteria and viruses while preventing potential discomfort and face skin allergy during long-period wearing. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical properties (e.g., stiffness, stretchability) of prefabricated hydrogels are of pivotal importance for diverse applications in tissue engineering, soft robotics, and medicine. This study reports a feasible method to fabricate ultrasoft and highly stretchable structures from stiff and tough hydrogels of low stretchability and the application of these switchable hydrogels in programmable shape‐morphing systems. Stiff and tough hydrogel structures are first fabricated by the mechanical strengthening of Ca2+‐alginate/polyacrylamide tough hydrogels by addition of Fe3+ ions, which introduces Fe3+ ionically cross‐linked centers into the Ca2+ divalent cross‐linked hydrogel, forming an additional and much less flexible trivalent ionically cross‐linked network. The resulting stiff and tough hydrogels are exposed to an L‐ascorbic acid (vitamin C, VC) solution to rapidly reduce Fe3+ to Fe2+. As a result, flexible divalent ionically cross‐linked networks are formed, leading to swift softening of the stiff and tough hydrogels. Moreover, localized stiffness variation of the tough hydrogels can be realized by precise patterning of the VC solution. To validate this concept, sequential steps of VC patterning are carried out for local tuning of the stiffness of the hydrogels. With this strategy, localized softening, unfolding, and sequential folding of the tough hydrogels into complex 3D structures is demonstrated. [ABSTRACT FROM AUTHOR]

Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti-freezing, non-drying CPA-based organohydrogels with long-term stability by partially displacing water molecules within the pre-fabricated hydrogels. CPAbased Ca-alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA-based organohydrogels remain unfrozen and mechanically flexible even up to @70 8C and are stable under ambient conditions or even vacuum. [ABSTRACT FROM AUTHOR]

Abstract: Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti‐freezing, non‐drying CPA‐based organohydrogels with long‐term stability by partially displacing water molecules within the pre‐fabricated hydrogels. CPA‐based Ca‐alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA‐based organohydrogels remain unfrozen and mechanically flexible even up to −70 °C and are stable under ambient conditions or even vacuum. [ABSTRACT FROM AUTHOR]

The deposition of diamond coatings is often impaired by poor adhesion on hard metal substrates. To enhance the adhesion of diamond coatings on Co-cemented tungsten carbide (WC-Co), TiB 2 thin films (100 nm to 1 μm in thickness) were deposited as interlayers by magnetron sputtering. Diamond coatings were continuously, densely and quickly deposited on the TiB 2 interlayers. The adhesion of the diamond coatings evaluated by Rockwell C indentation, was enhanced by utilizing TiB 2 interlayer with appropriate thickness compared to that without interlayer. The barrier function of the interlayer versus cobalt is dependent on the thickness of the TiB 2 interlayer. As observed by scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS), the cobalt diffusion was effectively hindered by utilizing TiB 2 interlayers with a thickness greater than 200 nm, whereas the strongest film adhesion was obtained for the TiB 2 interlayer with thickness of ca. 200 nm. Furthermore, the thickness of the deposited diamond film was 1.7 times higher than that of the diamond film grown without TiB2 interlayer, indicating an accelerated growth. Raman spectroscopy and X-ray diffraction (XRD) analyses demonstrated the existence of TiB 2 and high quality of diamond films. This work indicates that thin TiB 2 interlayers are promising candidates for achieving adherent diamond coated cutting tools, such as micro-drills and milling tools. [ABSTRACT FROM AUTHOR]

Abstract: Nontoxic liquid metals (conductive materials in a liquid state at room temperature) are an emerging class of materials for applications ranging from soft electronics and robotics to medical therapy and energy devices. Their sticky and corrosive properties, however, are becoming more of a critical concern for circuits and devices containing other metals as these are easily destroyed or contaminated by the liquid metals. Herein, a feasible method for fabricating highly conductive graphene‐coated liquid metal (GLM) droplets is reported and their application as nonstick, noncorrosive, movable, soft contacts for electrical circuits is demonstrated. The as‐prepared GLM droplets consist of a liquid‐phase soft core of liquid metal and a slippery outer layer of graphene sheets. These structures address the issue of simultaneous control of the wettability and conductivity of a soft electronic contact by combining extraordinary properties, i.e., nonstick, noncorrosive, yet exhibiting high electronic conductivity while in contact with metal substrates, e.g., Au, Cu, Ag, and Ni. As proof‐of‐concept, the as‐prepared GLM droplets are demonstrated as floating electrodes for movable, recyclable electronic soft contacts in electrical circuits. [ABSTRACT FROM AUTHOR]

According to the differential information of four homologous oligonucleotides, two domain-based encoders have been constructed with the molecular information as the input. Based on the one-to-one correspondence between the input and output, SNVs can be identified and their sites can be located at the domain level. [ABSTRACT FROM AUTHOR]

A novel bifunctional organic sponge photocatalyst can enable the efficient coupling of tertiary amines with ketones in water. The asymmetric transformation can be also achieved by using this sponge photocatalyst. [ABSTRACT FROM AUTHOR]

Nanocrystalline diamond particles are promising candidates for copious applications in materials science, biology and electronics. In this work, diamond nucleation density was unprecedentedly enhanced via a non-invasive electrostatic self-assembly seeding approach. By addition of glutamic acid to the nanodiamond seeding solution, the positively charged amino-group of glutamic acid, which is adsorbed on nanodiamond particles, enhances the adsorption on negative charged cemented carbide substrate. The highest nucleation density (1.0 × 10 10 cm −2 ) was achieved by utilizing glutamic acid at pH 4 as well as DI water at pH 2.2. This density was 20–1000 times higher than most earlier published results on WC-Co substrate. The concentration of the organic molecule, pH, concentration of ND particles and ultrasonication seeding time were found to be important for the seeding process. The colloidal stability was tweaked by pH of the dispersion and concentration of glutamic acid. The optimized parameters for nanodiamond adsorption on WC-Co substrate were found to be pH 4 at a concentration of 7 × 10 −5 M of glutamic acid at a nanodiamond concentration of 0.005 wt%, while the seeding was conducted for 30 min. The short ultrasonication time inhibits aggregation and void formation due to peeling off of nanodiamond patches at prolonged seeding times. Moreover, diamond thin films were deposited uniformly and densely on end mills made of cemented carbide. This work indicates that electrostatic induced adsorption of diamond nanoparticles is crucial for the development of ultra-high nucleation densities for the growth of high performance nanocrystalline diamond films, especially for micro sized tools with sharp cutting edges. It may serve as an approach for pinhole-free ultra-thin films deposition on micro-electromechanical system, and encapsulation coating in harsh environment. [ABSTRACT FROM AUTHOR]

Colloidal stability of nanoparticles with particle sizes smaller than 100 nm is a critical issue for various research areas, including material science, electronics and biomedicine. We propose a facile, fast and cost-efficient method to increase the colloidal stability by simply adding organic molecules as ligands, which adsorb to the nanoparticle surface subsequently. Citric acid, oxalic acid, glutamic acid and propylamine were found to stabilize the nanodiamond (ND) particles with a mean diameter of approx. 30–100 nm. The charge of the particles could be controlled by the pH of the dispersions and by stabilizing with carboxylic acids or amino acids mentioned above. ND particles stabilized with citric acid and oxalic acid at a pH higher than 2.5 were negatively charged, while ND dispersions stabilized with glutamic acid were charged positively below a pH of 3.2. Furthermore, the stability of the dispersion was found to be dependent on the concentration of the stabilizing agent and the pH of the dispersion. Finally, we proposed the stabilizing mechanism of ND particles with propylamine. Glutamic acid and propylamine stabilized ND dispersions can be utilized for high seeding densities on negatively charged surfaces due to the amino-groups, which can be helpful for adsorption processes in electronics and material science. Due to the high biocompatibility, non-cytotoxicity and chemical inertness of ND particles, carboxylic acids and amino acids stabilized ND particles are envisaged to be useful in the biomedical field, i.e. bio-labels, drug delivery vehicles, and effective enterosorbent. [ABSTRACT FROM AUTHOR]

The successfully developed polydimethylsiloxane (PDMS, a green and highly transparent polymer material) sponge photocatalyst can catalyze cross-dehydrogenative coupling (CDC) of tertiary amines and various nucleophiles with high efficiency and reusability under visible light irradiation. Through an easy-to-build continuous flow reactor, the sponge photocatalytic reaction can be facilely scaled up. [ABSTRACT FROM AUTHOR]

Herein we propose a hybridization chain reaction based kinetics competition strategy able to recognize the combination/sequence of input signals. Further, a DNA priority encoder and a keypad lock were constructed. This strategy allowed us to develop a one-pot assay that can automatically and smartly respond to multiple inputs. [ABSTRACT FROM AUTHOR]

This study presents the synthesis and characterization of a novel glucose electrochemical biosensor based on gold nanoparticles/bovine serum albumin/Fe 3 O 4 (AuNPs/BSA/Fe 3 O 4 ) composite nanoparticles. The prepared magnetic composite nanoparticles consist of a BSA protein shell, providing biocompatible environment for enzyme immobilization. Furthermore, in situ immobilization of gold nanoparticles greatly enhances the performance of electron transfer. Using these composite nanoparticles, the model enzyme, glucose oxidase (GOx) was readily adsorbed to surface so as the GOx/AuNPs/BSA/Fe 3 O 4 electrochemical biosensor was developed. The electrochemical performance of the biosensor was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. Under the optimal preparation conditions, the resultant biosensor has a short response time of 0.8 s, an excellent sensitivity of 115.3 μA mM −1 cm −2 , and a linear dynamic range from 0.25 to 7.0 mM with a low detection limit of 3.54 μM (S/N = 3). The high sensitivity, good reproducibility and stability of the biosensor presented in this study show that the as-prepared AuNPs/BSA/Fe 3 O 4 composite nanoparticles are a promising material for the development and construction of biosensors. [ABSTRACT FROM AUTHOR]

This article describes a low-temperature thermal stabilization method, for the efficient preparation of polyacrylontrile (PAN)-based carbon fibers with improved mechanical properties. In this method, bundles of regular PAN precursor fibers were firstly heated and stored in air for 30 days at 120 °C to cyclise the nitrile groups and oxidize the PAN backbone. A further stabilization above 200 °C in air made the pretreated fibers fully stabilized. Structural changes of the as-made PAN fibers were observed by Fourier Transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetry and dynamic mechanical analysis. Microvoid evolutions of the fibers during stabilization and carbonization process were studied by synchrotron small-angle X-ray scattering. Our results showed that the initiation of the cyclization and oxidation reaction at 120 °C not only restricts the disorientation of PAN molecules but also reduces the pyrolysis of molecular chains at higher temperatures in the carbonization process. Hence, preferred orientation of crystallites and char yield increased. Moreover, microvoid defects were significantly reduced, leading to a significant improvement of the mechanical properties (a 16% increment in the tensile strength). [ABSTRACT FROM AUTHOR]

This paper describes a fully aqueous- and air-compatible chemical approach to preparing high-performance conductive textiles. In this method, the surfaces of textile materials are first modified with an aqueous solution of double-bond-containing silane molecules to form a surface-anchoring layer for subsequent in situ free-radical polymerization of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) in the air. Thin layers of poly-METAC (PMETAC) are therefore covalently grafted on top of the silane-modified textile surface. Cu- or Ni-coated textiles are finally fabricated by electroless deposition (ELD) onto the PMETAC-modified textiles. Parameters including polymerization time, temperature, and ELD conditions are studied to optimize the whole fabrication process. The as-made conductive textiles exhibit sheet resistance as low as 0.2 Ω sq−1, which makes them highly suitable for use as conductive wires and interconnects in flexible and wearable electronic devices. More importantly, the chemical method is fully compatible with the conventional 'pad-dry-cure' fabrication process in the textile manufacturing industry, thus indicating that it is very promising for high-throughput and roll-to-roll fabrication of high-performance metal-coated conductive textiles in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Intrinsically adhesive and temperature tolerant flexible sensors are fabricated. • Strain sensor achieves a GF of 2.58 and a sensing range of 0–1000%. • Reliefs on electrodes lead to a GF of 2.14 kPa−1 for pressure sensor. • Wireless strain sensor is demonstrated based on a bluetooth protocol. Hydrogel-based flexible sensors are of promising applications in various fields, but fabrication of such sensors with integrated high performances remains a challenge. In this work, flexible sensors (both strain sensors and pressure sensors) with integrated high performances are fabricated utilizing double network (DN) organohydrogels. Because of the unique structure of DN organohydrogels, the flexible sensors exhibit intrinsic adhesion without introducing components that are often used to obtain adhesive hydrogels, such as polydopamine, nucleobases or proteins. In addition, outstanding temperature tolerance (−18 to 80 °C), high stretchability (>2000%), tensile strength (>300 kPa), self-healing ability (96.5%) and transparency (90%) are also achieved. Resistive-type strain sensors of DN organohydrogels achieve high gauge factor (GF = 2.58), low response time (0.18 s), large sensing range (0–1000%) and reversible sensing ability (>1000 cycles). Sandwich-shaped capacitive-type pressure sensors comprising DN organohydrogel electrodes with reliefs exhibit a high sensitivity of 2.14 kPa−1. Such flexible sensors can be applied in monitoring various human motions and subtle physiological activities and further promoted as wireless sensors on the basis of a Bluetooth protocol. [ABSTRACT FROM AUTHOR]

Mechanically controlled polymerization that employs the mechanical energy to fabricate novel synthetic materials has attracted considerable interest. However, only a few examples have been achieved so far, owing to the limited choices of materials and strategies. Herein, a versatile, liquid metal (LM)‐mediated mechanochemical polymerization method (LMMMP) is developed for the air‐compatible, robust preparation of polymers in an aqueous solution. This method involves the simultaneous disruption of bulk LMs into micro‐ and nanodroplets and the combination of monomers into polymers during ultrasonic irradiation. The pristine and reactive LM surface continuously generated by ultrasound endows this polymerization method with excellent oxygen tolerance, high reaction rate, and the ability to produce polymers with high molecular weight from a wide variety of water‐soluble monomers. Besides, LM droplets are readily reclaimed and reused for polymerization. The authors envision that the LMMMP promotes the utilization of mechanical energy for the synthesis of functional polymers, constitutes a novel fabrication approach for polymer–LM nanocomposites, and provides new insight into the design of LM‐based platforms for polymerization. [ABSTRACT FROM AUTHOR]

Liquid Metal-Mediated Mechanochemical Polymerization B Front Cover b : In article number 1900537, Xuechang Zhou and co-workers report a liquid-metal-mediated mechanochemical polymerization method for the air-compatible and robust preparation of polymers in an aqueous solution. By applying sonication, bulk liquid metals are disrupted into micro- and nanodroplets, and simultaneously, polymers are synthesized. [Extracted from the article]

Transient electronics, arising electronic devices with dissolvable or degradable features on demand, is still at an early stage of development due to the limited choices of materials and strategies. Herein, a facile fabrication method for transient circuits by the combination of room‐temperature liquid metals (RTLMs) as the electronic circuit and water‐soluble poly(vinyl alcohol) (PVA) as the packaging material is reported. The as‐made transient circuits exhibit remarkable durability and stable electric performance upon bending and twisting, while possessing short transience times, owing to the excellent solubility of PVA substrates and the intrinsic flexibility of RTLM patterns. Moreover, the RTLM‐based transient circuit shows an extremely high recycling efficiency, up to 96% of the employed RTLM can be recovered. As such, the economic and environmental viability of transient electronics increases substantially. To validate this concept, the surface patterning of RTLMs with complicated shapes is demonstrated, and a transient antenna is subsequently applied for passive near‐field communication tag and a transient capacitive touch sensor. The application of the RTLM‐based transient circuit for sequentially turning off an array of light‐emitting‐diode lamps is also demonstrated. The present RTLM‐based PVA‐encapsulated circuits substantially expand the scope of transient electronics toward flexible and recyclable transient systems. Flexible and recyclable transient circuits are fabricated by employing room‐temperature liquid metals as the electronic circuit and water‐soluble poly(vinyl alcohol) as the packaging material. The as‐made transient circuits are successfully applied to various electronic devices, including near‐field communication, capacitive touch sensors, and transient circuits to allow sequentially turning off an array of light‐emitting‐diode lamps. [ABSTRACT FROM AUTHOR]

Living biological tissues are made of structures with properly defined mechanical properties (toughness and stiffness) toward specific biological functions. Herein, a chemical manipulation strategy is developed to locally vary the oxidation state of Fe ions from divalent to trivalent in the tough hydrogels. The resultant trivalent ionically cross‐linked networks become less flexible and lead to a significant enhancement of the stiffness of the tough hydrogels. The mechanical strengthening of Fe2+/Ca2+‐alginate/polyacrylamide tough hydrogels is demonstrated by the oxidation with ammonium persulfate (APS). Moreover, by applying surface patterning, the mechanical properties of the tough hydrogels are spatially stiffened and thus can serve as anisotropic elements to guide the shape morphing of tough hydrogels into complex 3D structures. This method opens up a simple strategy not only to dynamically vary the mechanics of tough hydrogels, both in bulk and locally from prefabricated soft tough hydrogels, but also toward their shape morphing behaviors on demand. Stiffening and shape morphing of soft Fe2+/Ca2+‐alginate/polyacrylamide tough hydrogels is achieved by applying a chemical manipulation method to localized varying the oxidation state of Fe ions from divalent to trivalent. With this method, 3D molding or shape morphing of tough hydrogels is realized by the as‐encoded mechanical anisotropy. [ABSTRACT FROM AUTHOR]

Correction for 'Bifunctional organic sponge photocatalyst for efficient cross-dehydrogenative coupling of tertiary amines to ketones' by Teng Zhang et al., Chem. Commun., 2017, 53, 12536–12539. [ABSTRACT FROM AUTHOR]