2019, Wang, Y., Kang, V., Arzt, E., Federle, W., Hensel, R.

Recent advances in bio-inspired microfibrillar adhesives have resulted in technologies that allow reliable attachment to a variety of surfaces. Because capillary and van der Waals forces are considerably weakened underwater, fibrillar adhesives are however far less effective in wet environments. Although various strategies have been proposed to achieve strong reversible underwater adhesion, strong adhesives that work both in air and underwater without additional surface treatments have yet to be developed. In this study, we report a novel design - cupped microstructures (CM) - that generates strong controllable adhesion in air and underwater. We measured the adhesive performance of cupped polyurethane microstructures with three different cup angles (15, 30, and 45°) and the same cup diameter of 100 μm in dry and wet conditions in comparison to standard mushroom-shaped microstructures (MSMs) of the same dimensions. In air, 15°CM performed comparably to the flat MSM of the same size with an adhesion strength (force per real contact area) of up to 1.3 MPa, but underwater, 15°CM achieved 20 times stronger adhesion than MSM (∼1 MPa versus ∼0.05 MPa). Furthermore, the cupped microstructures exhibit self-sealing properties, whereby stronger pulls lead to longer stable attachment and much higher adhesion through the formation of a better seal. © 2019 American Chemical Society.

2020, Ho, D.-K., Murgia, X., De Rossi, C., Christmann, R., Hüfner de Mello Martins, A.G., Koch, M., Andreas, A., Herrmann, J., Müller, R., Empting, M., Hartmann, R.W., Desmaele, D., Loretz, B., Couvreur, P., Lehr, C.-M.

Elimination of pulmonary Pseudomonas aeruginosa (PA) infections is challenging to accomplish with antibiotic therapies, mainly due to resistance mechanisms. Quorum sensing inhibitors (QSIs) interfering with biofilm formation can thus complement antibiotics. For simultaneous and improved delivery of both active agents to the infection sites, self-assembling nanoparticles of a newly synthesized squalenyl hydrogen sulfate (SqNPs) were prepared. These nanocarriers allowed for remarkably high loading capacities of hydrophilic antibiotic tobramycin (Tob) and a novel lipophilic QSI at 30 % and circa 10 %, respectively. The drug-loaded SqNPs showed improved biofilm penetration and enhanced efficacy in relevant biological barriers (mucin/human tracheal mucus, biofilm), leading to complete eradication of PA biofilms at circa 16-fold lower Tob concentration than Tob alone. This study offers a viable therapy optimization and invigorates the research and development of QSIs for clinical use.

2020, Liang, Mingxing, Wang, Lei, Presser, Volker, Dai, Xiaohu, Yu, Fei, Ma, Jie

The recent advances in chloride‐ion capturing electrodes for capacitive deionization (CDI) are limited by the capacity, rate, and stability of desalination. This work introduces Ti3C2Tx/Ag synthesized via a facile oxidation‐reduction method and then uses it as an anode for chloride‐ion capture in CDI. Silver nanoparticles are formed successfully and uniformly distributed with the layered‐structure of Ti3C2Tx. All Ti3C2Tx/Ag samples are hydrophilic, which is beneficial for water desalination. Ti3C2Tx/Ag samples with a low charge transfer resistance exhibit both pseudocapacitive and battery behaviors. Herein, the Ti3C2Tx/Ag electrode with a reaction time of 3 h exhibits excellent desalination performance with a capacity of 135 mg Cl− g−1 at 20 mA g−1 in a 10 × 10−3 m NaCl solution. Furthermore, low energy consumption of 0.42 kWh kg−1 Cl− and a desalination rate of 1.5 mg Cl− g−1 min−1 at 50 mA g−1 is achieved. The Ti3C2Tx/Ag system exhibits fast rate capability, high desalination capacity, low energy consumption, and excellent cyclability, which can be ascribed to the synergistic effect between the battery and pseudocapacitive behaviors of the Ti3C2Tx/Ag hybrid material. This work provides fundamental insight into the coupling of battery and pseudocapacitive behaviors during Cl− capture for electrochemical desalination.

2019, Khan, Arshad, Roo, Joan Sol, Kraus, Tobias, Steimle, Jürgen

Despite the increasing popularity of soft interactive devices, their fabrication remains complex and time consuming. We contribute a process for rapid do-it-yourself fabrication of soft circuits using a conventional desktop inkjet printer. It supports inkjet printing of circuits that are stretchable, ultrathin, high resolution, and integrated with a wide variety of materials used for prototyping. We introduce multi-ink functional printing on a desktop printer for realizing multi-material devices, including conductive and isolating inks. We further present DIY techniques to enhance compatibility between inks and substrates and the circuits' elasticity. This enables circuits on a wide set of materials including temporary tattoo paper, textiles, and thermoplastic. Four application cases demonstrate versatile uses for realizing stretchable devices, e-textiles, body-based and re-shapeable interfaces.

2020, Liu, Zhen, Zhang, Peng, Pyttlik, Andrea, Kraus, Tobias, Volmer, Dietrich A.

Gold nanoparticles (AuNP) are frequently used in surface‐assisted laser desorption/ionization mass spectrometry (SALDI‐MS) for analysis of biomolecules because they exhibit suitable thermal and chemical properties as well as strong surface plasmonic effects. Moreover, the structures of AuNP can be controlled by well‐established synthesis protocols. This was important in the present work, which studied the influence of the nanoparticles’ structures on atmospheric pressure (AP)‐SALDI‐MS performance. A series of AuNP with different core sizes and capping ligands were investigated, to examine the desorption/ionization efficiency (DIE) under AP‐SALDI conditions. The results showed that both the AuNP core size as well as the nature of the surface ligand had a strong influence on DIE. DIE increased with the size of the AuNP and the hydrophobicity of the ligands. Chemical interactions between ligand and analytes also influenced DIE. Moreover, we discovered that removing the organic ligands from the deposited AuNP substrate layer by simple laser irradiation prior to LDI further amplified DIE values. The optimized AuNP were successfully used to analyze a wide arrange of different low molecular weight biomolecules as well as a crude pig brain extract, which readily demonstrated the ability of the technique to detect a wide range of lipid species within highly complex samples.

2019, Taverno, I., Rodrigo, A.M., Kandziora, M., Kuntz, S., Dernedde, J., Trautwein, C., Tacke, F., Blas-Garcia, A., Bartneck, M.

Due to their importance for the outcome of the inflammatory response, the motile myeloid cells are a focus of novel treatment options. The interplay of selectins and their ligands with leukocytes and endothelial cells, which mediate endothelial attachment and transmigration of immune cells, can be modulated by selectin‐binding structures. Here, a library of selectin‐targeting ligands coupled to either gold, silver, iron oxide nanospheres, or quantum dots of 5–10 nm in size is used to systematically study their impact on immune cell motility. The multivalent presentation of the carbohydrate mimetics results in very low sub‐nanomolar binding to L ‐selectin. Using human primary monocytes, granulocytes, lymphocytes, and macrophages, it is shown that the ligands exhibit only minor effects on uptake, whereas the motility of leukocytes is critically affected as observed in migration assays evaluated by flow cytometry. The carbohydrate mimetic ring structure, sulfation, in particular, and the degree of ligand presentation, are constituents which cohere in this process. Specific carbohydrate ligands can thus selectively regulate leukocyte subsets. These data form the basis for advanced immunotherapy which inhibits the amplification of inflammation by restricting leukocyte influx to injured tissue sites. Furthermore, the targeting ligands may complement existing treatment options for inflammatory diseases.

2019, Włodarczyk-Biegun, Malgorzata K., Paez, Julieta I., Villiou, Maria, Feng, Jun, del Campo, Aranzazu

Inspired by reversible networks present in nature, we have explored the printability of catechol functionalized polyethylene glycol (PEG) based inks with metal-coordination crosslinking. Material formulations containing Al3+, Fe3+ or V3+ as crosslinking ions were tested. The printability and shape fidelity were dependent on the ink composition (metal ion type, pH, PEG molecular weight) and printing parameters (extrusion pressure and printing speed). The relaxation time, recovery rate and viscosity of the inks were analyzed in rheology studies and correlated with thermodynamic and ligand exchange kinetic constants of the dynamic bonds and the printing performance (i.e. shape fidelity of the printed structures). The relevance of the relaxation time and ligand exchange kinetics for printability was demonstrated. Cells seeded on the crosslinked materials were viable, indicating the potential of the formulations to be used as inks for cell encapsulation. The proposed dynamic ink design offers significant flexibility for 3D (bio)printing, and enables straightforward adjustment of the printable formulation to meet application-specific needs.

2020, Han, L., Zheng, Y., Luo, H., Feng, J., Engstler, R., Xue, L., Jing, G., Deng, X., del Campo, A., Cui, J.

A solid-to-hollow evolution in macroscopic structures is challenging in synthetic materials. A fundamentally new strategy is reported for guiding macroscopic, unidirectional shape evolution of materials without compromising the material's integrity. This strategy is based on the creation of a field with a “swelling pole” and a “shrinking pole” to drive polymers to disassemble, migrate, and resettle in the targeted region. This concept is demonstrated using dynamic hydrogels containing anchored acrylic ligands and hydrophobic long alkyl chains. Adding water molecules and ferric ions (Fe3+) to induce a swelling–shrinking field transforms the hydrogels from solid to hollow. The strategy is versatile in the generation of various closed hollow objects (for example, spheres, helix tubes, and cubes with different diameters) for different applications.

2020, Yang, P., Zhang, L., Kang, D.J., Strahl, R., Kraus, T.

The direct printing of microscale quantum dot light-emitting diodes (QLEDs) is a cost-effective alternative to the placement of pre-formed LEDs. The quality of printed QLEDs currently is limited by nonuniformities in droplet formation, wetting, and drying during inkjet printing. Here, optimal ink formulation which can suppress nonuniformities at the pixel and array levels is demonstrated. A solvent mixture is used to tune the ejected droplet size, ensure wetting, and provoke Marangoni flows that prevent coffee stain rings. Arrays of green QLED devices are printed at a resolution of 500 pixels in.−1 with a maximum luminance of ≈3000 cd m−2 and a peak current efficiency of 2.8 cd A−1. The resulting array quality is sufficient to print displays at state-of-the-art resolutions.

2020, Mora-Boza, A., Włodarczyk-Biegun, M.K., Del Campo, A., Vázquez-Lasa, B., Román, J.S.

The fabrication of intricate and long-term stable 3D polymeric scaffolds by a 3D printing technique is still a challenge. In the biomedical field, hydrogel materials are very frequently used because of their excellent biocompatibility and biodegradability, however the improvement of their processability and mechanical properties is still required. This paper reports the fabrication of dual crosslinked 3D scaffolds using a low concentrated (<10 wt%) ink of gelatin methacryloyl (GelMA)/chitosan and a novel crosslinking agent, glycerylphytate (G1Phy) to overcome the current limitations in the 3D printing field using hydrogels. The applied methodology consisted of a first ultraviolet light (UV) photopolymerization followed by a post-printing ionic crosslinking treatment with G1Phy. This crosslinker provides a robust framework and avoids the necessity of neutralization with strong bases. The blend ink showed shear-thinning behavior and excellent printability in the form of a straight and homogeneous filament. UV curing was undertaken simultaneously to 3D deposition, which enhanced precision and shape fidelity (resolution ≈150 μm), and prevented the collapse of the subsequent printed layers (up to 28 layers). In the second step, the novel G1Phy ionic crosslinker agent provided swelling and long term stability properties to the 3D scaffolds. The multi-layered printed scaffolds were mechanically stable under physiological conditions for at least one month. Preliminary in vitro assays using L929 fibroblasts showed very promising results in terms of adhesion, spreading, and proliferation in comparison to other phosphate-based traditional crosslinkers (i.e. TPP). We envision that the proposed combination of the blend ink and 3D printing approach can have widespread applications in the regeneration of soft tissues.