Self-healing hydrogels attract broad attention as cell/drug carriers for direct injection into damaged tissues or as bioinks for three-dimensional (3D) printing of tissue-like constructs. For ...application in 3D printing, the self-healing hydrogels should maintain the steady rheological properties during printing process, and be further stabilized by secondary post-printing crosslinking. Here, a chitosan self-healing hydrogel is developed for injectable hydrogel and printable ink using phenol-functionalized chitosan and dibenzaldehyde-terminated telechelic poly(ethylene glycol). Phenol functionalization of chitosan can introduce unique interaction that allows the hydrogel to possess fast gelling rate, good self-healing ability, and long-range critical gel behavior, as well as secondary visible light-crosslinking capability. The hydrogel is easily pre-formed in a syringe and extruded through a 26-gauge needle to produce a continuous and stackable filament. The cell-laden hydrogel is successfully printed into a 3D construct. Moreover, the hydrogel is developed for modular 3D printing, where hydrogel modules (LEGO-like building blocks) are individually printed and assembled into an integrated construct followed by secondary visible light-crosslinking. The versatile phenol-functionalized chitosan self-healing hydrogel will open up numerous potential applications, particularly in 3D bioprinting and modular 3D bioprinting.
A White Random Laser Chang, Shu-Wei; Liao, Wei-Cheng; Liao, Yu-Ming ...
Scientific reports,
02/2018, Volume:
8, Issue:
1
Journal Article
Peer reviewed
Open access
Random laser with intrinsically uncomplicated fabrication processes, high spectral radiance, angle-free emission, and conformal onto freeform surfaces is in principle ideal for a variety of ...applications, ranging from lighting to identification systems. In this work, a white random laser (White-RL) with high-purity and high-stability is designed, fabricated, and demonstrated via the cost-effective materials (e.g., organic laser dyes) and simple methods (e.g., all-solution process and self-assembled structures). Notably, the wavelength, linewidth, and intensity of White-RL are nearly isotropic, nevertheless hard to be achieved in any conventional laser systems. Dynamically fine-tuning colour over a broad visible range is also feasible by on-chip integration of three free-standing monochromatic laser films with selective pumping scheme and appropriate colour balance. With these schematics, White-RL shows great potential and high application values in high-brightness illumination, full-field imaging, full-colour displays, visible-colour communications, and medical biosensing.
A new design concept for novel photoresponsive flash organic field‐effect transistor (OFET) memory is demonstrated by employing the carbazoledioxazine polymer (Poly CD) as an electret. Photoactive ...electrets that can absorb the light effectively rather than photoactive semiconductors are proposed by the “photoinduced recovery” mechanism in the literature; however, the correlation between the chemical structure and photoresponsive electrical performances is ambiguous. In this study, it is reported for the first time that the OFET memory with trapped charges can be optically recovered by a polymer electret and the working mechanism can be explained by the structural design. The highly planar Poly CD electret exhibits photoluminescence quenching in film states, resulting in the generation of sufficient excitons to eliminate trapped charges under light excitation. Additionally, the Poly CD electret with coplanar donor–acceptor moieties is suitable for both p‐channel and n‐channel semiconductors. For p‐type memory devices, a large memory window (82 V) and stable nonvolatile retention performance with high ON/OFF ratio could be obtained. The memories also display good switching reliability for voltage‐programming and light‐erasing cycles. This study provides useful information for the development of polymer‐based photoresponsive flash OFET memories and demonstrates the practical applications of photorecorder and photosensitive smart tag.
Novel photoresponsive flash memory devices based on a polymer electret, carbazoledioxazine polymer, shows an ambipolar nature and fast photoinduced recovery response. Moreover, the memory devices exhibit nonvolatile characteristics over 104 s with a high memory ratio of 103 and reliable durability under switching cycles, which potentially satisfy the requirements for the practical application of the photorecorder and photosensitive smart tag.
Bone is a natural composite of collagen protein and the mineral hydroxyapatite. The structure of bone is known to be important to its load-bearing characteristics, but relatively little is known ...about this structure or the mechanism that govern deformation at the molecular scale. Here we perform full-atomistic calculations of the three-dimensional molecular structure of a mineralized collagen protein matrix to try to better understand its mechanical characteristics under tensile loading at various mineral densities. We find that as the mineral density increases, the tensile modulus of the network increases monotonically and well beyond that of pure collagen fibrils. Our results suggest that the mineral crystals within this network bears up to four times the stress of the collagen fibrils, whereas the collagen is predominantly responsible for the material's deformation response. These findings reveal the mechanism by which bone is able to achieve superior energy dissipation and fracture resistance characteristics beyond its individual constituents.
Variable stoichiometry and silicate polymorphism in calcium-silicate-hydrates (C-S-H) has impeded the revelation of point defects distribution in the silicate tetrahedral network of C-S-H, which ...resembles tobermorite crystal structure with some bridging tetrahedra (BT) and paired tetrahedra (PT) vacancies in dreierketten chains. Here we use a computational approach to characterize silicate polymorphism by introducing the vacancy ratio of BT to PT (α) and establishing a three-term empirical mean chain length (MCL) formula for different calcium-to‑silicon ratios (Ca/Si) ranging from 1.2 to 2.3. The formula identifies BT and PT controls at low and high α respectively and allows an inverse mapping of polymorphic range based on NMR experiments. The proposed computational framework quantitatively describes silicate polymorphs and links NMR-measured MCL to C-S-H atomistic configurations at the molecular level.
Vegetable oil‐based feeds are regarded as an alternative source for the production of fuels and chemicals. Paraffins and olefins can be produced from these feeds through catalytic deoxygenation. The ...fundamentals of this process are mostly studied by using model compounds such as fatty acids, fatty acid esters, and specific triglycerides because of their structural similarity to vegetable oils. In this Review we discuss the impact of feedstock, reaction conditions, and nature of the catalyst on the reaction pathways of the deoxygenation of vegetable oils and its derivatives. As such, we conclude on the suitability of model compounds for this reaction. It is shown that the type of catalyst has a significant effect on the deoxygenation pathway, that is, group 10 metal catalysts are active in decarbonylation/decarboxylation whereas metal sulfide catalysts are more selective to hydrodeoxygenation. Deoxygenation studies performed under H2 showed similar pathways for fatty acids, fatty acid esters, triglycerides, and vegetable oils, as mostly deoxygenation occurs indirectly via the formation of fatty acids. Deoxygenation in the absence of H2 results in significant differences in reaction pathways and selectivities depending on the feedstock. Additionally, using unsaturated feedstocks under inert gas results in a high selectivity to undesired reactions such as cracking and the formation of heavies. Therefore, addition of H2 is proposed to be essential for the catalytic deoxygenation of vegetable oil feeds.
Deoxygenation—yes or no? The deoxygenation of vegetable oil‐based feeds is mostly studied using model compounds. Reactions in the presence and absence of H2 show possible deoxygenation pathways and intermediates for the different model compounds. By studying the influence of the type of catalyst, reaction atmosphere, feedstock, and its degree of unsaturation on the deoxygenation pathways we conclude on the suitability of model compounds for the deoxygenation of vegetable oil‐based feeds.
Water is an important component of collagen in tendons, but its role for the function of this load-carrying protein structure is poorly understood. Here we use a combination of multi-scale ...experimentation and computation to show that water is an integral part of the collagen molecule, which changes conformation upon water removal. The consequence is a shortening of the molecule that translates into tensile stresses in the range of several to almost 100 MPa, largely surpassing those of about 0.3 MPa generated by contractile muscles. Although a complete drying of collagen would be relevant for technical applications, such as the fabrication of leather or parchment, stresses comparable to muscle contraction already occur at small osmotic pressures common in biological environments. We suggest, therefore, that water-generated tensile stresses may play a role in living collagen-based materials such as tendon or bone.
Two-dimensional spiral plasmonic structures have emerged as a versatile approach to generate near-field vortex fields with tunable topological charges. We demonstrate here a far-field approach to ...observe the chiral second-harmonic generation (SHG) at designated visible wavelengths from a single plasmonic vortex metalens. This metalens comprises an Archimedean spiral slit fabricated on atomically flat aluminum epitaxial film, which allows for precise tuning of plasmonic resonances and subsequent transfer of two-dimensional materials on top of the spiral slit. The nonlinear optical measurements show a giant SHG circular dichroism. Furthermore, we have achieved an enhanced chiral SHG conversion efficiency (about an order of magnitude greater than the bare aluminum lens) from monolayer tungsten disulfide (WS2)/aluminum metalens, which is designed at the C-exciton resonance of WS2. Since the C-exciton is not a valley exciton, the enhanced chiral SHG in this hybrid system originates from the plasmonic vortex field-enhanced SHG under the optical spin–orbit interaction.
In this article, we propose heterojunction bipolar light-emitting transistors (HBLETs) with a staircase quantum well (QW) into the base region and investigate the temperature-dependent current gain ...of HBLET under different substrate temperatures. Our measured experimental results indicate a significant increase in current gain of approximately 73.23% at the base current, I <inline-formula> <tex-math notation="LaTeX">_{\textit{B}}</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">=</tex-math> </inline-formula> 0.2 mA, and base-to-collector voltage, V <inline-formula> <tex-math notation="LaTeX">_{\text{CE}}</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">=</tex-math> </inline-formula> 2 V, as the temperature of HBLET is increased from 25 <inline-formula> <tex-math notation="LaTeX">^{\circ}</tex-math> </inline-formula>C to 85 <inline-formula> <tex-math notation="LaTeX">^{\circ}</tex-math> </inline-formula>C. This behavior is opposite to that of conventional heterojunction bipolar transistors (HBTs) and is primarily attributed to electrons escaping from the InGaAs QW more quickly at higher temperatures. We propose a modified charge-control model based on QW thermionic emission theory to analyze this unique temperature-dependent current gain phenomenon. The experimental results are consistent with the simulation results, and thus, this study suggests that HBLETs have the potential for design the front end of smart thermal sensors.
Optical super-resolution microscopy allows nanoscale imaging of protein molecules in intact biological tissues. However, it is still challenging to perform large volume super-resolution imaging for ...entire animal organs. Here we develop a single-wavelength Bessel lightsheet method, optimized for refractive-index matching with clarified specimens to overcome the aberrations encountered in imaging thick tissues. Using spontaneous blinking fluorophores to label proteins of interest, we resolve the morphology of most, if not all, dopaminergic neurons in the whole adult brain (3.64 × 10
µm
) of Drosophila melanogaster at the nanometer scale with high imaging speed (436 µm
per second) for localization. Quantitative single-molecule localization reveals the subcellular distribution of a monoamine transporter protein in the axons of a single, identified serotonergic Dorsal Paired Medial (DPM) neuron. Large datasets are obtained from imaging one brain per day to provide a robust statistical analysis of these imaging data.
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