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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]

[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]

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]

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]

[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]

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]

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]

[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]

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]