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- ItemWet-Spinning of Biocompatible Core–Shell Polyelectrolyte Complex Fibers for Tissue Engineering(Weinheim : Wiley-VCH, 2020) Cui, Qing; Bell, Daniel Josef; Rauer, Sebastian Bernhard; Wessling, MatthiasPolyelectrolyte complex fibers (PEC fibers) have great potential with regard to biomedical applications as they can be fabricated from biocompatible and water-soluble polyelectrolytes under mild process conditions. The present publication describes a novel method for the continuous fabrication of PEC fibers in a water-based wet-spinning process by interfacial complexation within a core–shell spinneret. This process combines the robustness and flexibility of nonsolvent-induced phase separation (NIPS) spinning processes conventionally used in the membrane industry with the complexation between oppositely charged polyelectrolytes. The produced fibers demonstrate a core–shell structure with a low-density core and a highly porous polyelectrolyte complex shell of ≈800 μm diameter. In the case of chitosan and polystyrene sulfonate (PSS), mechanical fiber properties could be enhanced by doping the PSS with poly(ethylene oxide) (PEO). The resulting CHI/PSS-PEO fibers present a Young modulus of 3.78 GPa and a tensile strength of 165 MPa, which is an excellent combination of elongation at break and break stress compared to literature. The suitability of the CHI/PSS-PEO fibers as a scaffold for cell culture applications is verified by a four-day cultivation of human HeLa cells on PEO-reinforced fibers with a subsequent analysis of cell viability by fluorescence-based live/dead assay. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemTunable Photomechanics in Diarylethene-Driven Liquid Crystal Network Actuators(Washington, DC : ACS Publications, 2020) Lahikainen, Markus; Kuntze, Kim; Zeng, Hao; Helantera, Seidi; Hecht, Stefan; Priimagi, ArriThe response of soft actuators made of stimuli-responsive materials can be phenomenologically described by a stimulus-deformation curve, depicting the controllability and sensitivity of the actuator system. Manipulating such stimulus-deformation curve allows fabricating soft microrobots with reconfigurable actuation behavior, which is not easily achievable using conventional materials. Here, we report a light-driven actuator based on a liquid crystal polymer network containing diarylethene (DAE) photoswitches as cross-links, in which the stimulus-deformation curve under visible-light illumination is tuned with UV light. The tuning is brought about by the reversible electrocyclization of the DAE units. Because of the excellent thermal stability of the visible-absorbing closed-form DAEs, the absorbance of the actuator can be optically fixed to a desired value, which in turn dictates the efficiency of photothermally induced deformation. We employ the controllability in devising a logical AND gate with macroscopic output, i.e., an actuator that bends negligibly under UV or visible light irradiation, but with profound shape change when addressed to both simultaneously. The results provide design tools for reconfigurable microrobotics and polymer-based logic gating. © 2020 American Chemical Society. All rights reserved.
- Item4D Printing of a Light-Driven Soft Actuator with Programmed Printing Density(Washington, DC : ACS Publications, 2020) Nishiguchi, Akihiro; Zhang, Hang; Schweizerhof, Sjören; Schulte, Marie Friederike; Mourran, Ahmed; Möller, MartinThere is a growing interest in the concept of four-dimensional (4D) printing that combines a three-dimensional (3D) manufacturing process with dynamic modulation for bioinspired soft materials exhibiting more complex functionality. However, conventional approaches have drawbacks of low resolution, control of internal micro/nanostructure, and creation of fast, complex actuation due to a lack of high-resolution fabrication technology and suitable photoresist for soft materials. Here, we report an approach of 4D printing that develops a bioinspired soft actuator with a defined 3D geometry and programmed printing density. Multiphoton lithography (MPL) allows for controlling printing density in gels at pixel-by-pixel with a resolution of a few hundreds of nanometers, which tune swelling behaviors of gels in response to external stimuli. We printed a 3D soft actuator composed of thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) and gold nanorods (AuNRs). To improve the resolution of printing, we synthesized a functional, thermoresponsive macrocrosslinker. Through plasmonic heating by AuNRs, nanocomposite-based soft actuators undergo nonequilibrium, programmed, and fast actuation. Light-mediated manufacture and manipulation (MPL and photothermal effect) offer the feasibility of 4D printing toward adaptive bioinspired soft materials. Copyright © 2020 American Chemical Society.
- ItemOligothiophene-Based Phosphonates for Surface Modification of Ultraflat Transparent Conductive Oxides(Weinheim : Wiley-VCH, 2020) Timpel, Melanie; Nardi, Marco V.; Wegner, Berthold; Ligorio, Giovanni; Pasquali, Luca; Hildebrandt, Jana; Pätzel, Michael; Hecht, Stefan; Ohta, Hiromichi; Koch, NorbertThe self-assembly of electroactive organic molecules on transparent conductive oxides is a versatile strategy to engineer the interfacial energy-level alignment and to enhance charge carrier injection in optoelectronic devices. Via chemical grafting of an aromatic oligothiophene molecule by changing the position of the phosphonic acid anchoring group with respect to the organic moiety (terminal and internal), the direction of the main molecular dipole is changed, i.e., from parallel to perpendicular to the substrate, to study the molecular arrangement and electronic properties at the organic–inorganic interface. It is found that the observed work function increase cannot solely be predicted based on the calculated molecular dipole moment of the oligothiophene-based phosphonates. In addition, charge transfer from the substrate to the molecule has to be taken into account. Molecular assembly and induced electronic changes are analogous for both indium-tin oxide (ITO) and zinc oxide (ZnO), demonstrating the generality of the approach and highlighting the direct correlation between molecular coverage and electronic effects. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemExperimental and Computational Study on the Microfluidic Control of Micellar Nanocarrier Properties(Washington, DC : ACS Publications, 2021) Rezvantalab, Sima; Maleki, Reza; Drude, Natascha Ingrid; Khedri, Mohammad; Jans, Alexander; Moraveji, Mostafa Keshavarz; Darguzyte, Milita; Ghasemy, Ebrahim; Tayebi, Lobat; Kiessling, FabianMicrofluidic-based synthesis is a powerful technique to prepare well-defined homogenous nanoparticles (NPs). However, the mechanisms defining NP properties, especially size evolution in a microchannel, are not fully understood. Herein, microfluidic and bulk syntheses of riboflavin (RF)-targeted poly(lactic-co-glycolic acid)-poly(ethylene glycol) (PLGA-PEG-RF) micelles were evaluated experimentally and computationally. Using molecular dynamics (MD), a conventional "random"model for bulk self-assembly of PLGA-PEG-RF was simulated and a conceptual "interface"mechanism was proposed for the microfluidic self-assembly at an atomic scale. The simulation results were in agreement with the observed experimental outcomes. NPs produced by microfluidics were smaller than those prepared by the bulk method. The computational approach suggested that the size-determining factor in microfluidics is the boundary of solvents in the entrance region of the microchannel, explaining the size difference between the two experimental methods. Therefore, this computational approach can be a powerful tool to gain a deeper understanding and optimize NP synthesis. © 2021 The Authors. Published by American Chemical Society.