Hybrid Living Capsules Autonomously Produced by Engineered Bacteria

Bacterial cellulose (BC) has excellent material properties and can be produced cheaply and sustainably through simple bacterial culture, but BC-producing bacteria lack the extensive genetic toolkits of model organisms such as Escherichia coli. Here, we describe a simple approach for producing highly programmable BC materials through incorporation of engineered E. coli. The acetic acid bacterium Gluconacetobacter hansenii was co-cultured with engineered E. coli in droplets of glucose-rich media to produce robust cellulose capsules, which were then colonized by the E. coli upon transfer to selective lysogeny broth media. We show that the encapsulated E. coli can produce engineered protein nanofibers within the cellulose matrix, yielding hybrid capsules capable of sequestering specific biomolecules from the environment and enzymatic catalysis. Furthermore, we produced capsules capable of altering their own bulk physical properties through enzyme-induced biomineralization. This novel system, based on autonomous biological fabrication, significantly expands the functionality of BC-based living materials.

Micro- and Macromechanical Properties of a Composite with a Ternary PLA–PCL–TPS Matrix Reinforced with Short Fique Fibers

Biocomposites were prepared from a ternary matrix of polylactic acid (PLA), polycaprolactone (PCL), and thermoplastic starch (TPS) and reinforced with native fique fibers from southwestern Colombia. The influence of surface modification by alkalization of fique fibers on the interfacial properties of the biocomposite was studied using pull-out tests. Additionally, the effect of short fique fibers in three proportions (10%, 20%, and 30% (w/w)) on the tensile mechanical properties of the composite was evaluated. The experimental results indicated that the interfacial shear strength (IFSS) of the ternary matrix was predominantly influenced by PCL and characterized by the development of a weak interface that failed due to matrix yielding. Furthermore, the incorporation of short fique fibers increased the elastic modulus of the composite to values similar to those estimated with the Tsai–Pagano model. The alkalization treatment of the fique fibers improved the interface with the composite matrix, and this phenomenon was evidenced by the results of the micromechanical and tensile characterizations of the composite.

Polarimetry for Photonic Integrated Circuits

Photonic integrated circuits (PICs) play a key role in a wide range of applications. Very often, the performance of PICs depends strongly on the state of polarization of light. Classically, this is regarded as undesirable, but more and more applications emerge that make explicit use of polarization dependence. In either case, the characterization of the polarization properties of a PIC can be a nontrivial task. We present a way of characterizing PICs in terms of their full Müller matrix, yielding a complete picture of their polarization properties. The approach is demonstrated by carrying out measurements of fabricated PICs.

Structure and Stability of C:H:O Plasma Polymer Films Co-Polymerized Using Dimethyl Carbonate

C:H:O plasma polymer films (PPFs) were deposited by means of plasma-enhanced chemical vapour deposition using the non-toxic, biodegradable organic compound dimethyl carbonate (DMC) at various plasma powers and pressures in order to control the degradation properties related to the carbonate ester group. Coating properties using pure DMC monomer vapours were compared to co-polymerized films from gaseous mixtures of DMC with either ethylene (C2H4) or carbon dioxide (CO2) affecting deposition rate and chemical composition. C:H:O film properties were found to depend primarily on the amount of oxygen in the plasma. To investigate the PPF stability during aging, changes in the composition and properties were studied during their storage both in air and in distilled water over extended periods up to 5 months. It was shown that aging of the films is mostly due to oxidation of the plasma polymer matrix yielding slow degradation and decomposition. The aging processes and their rate are dependent on the intrinsic amount of oxygen in the as-prepared C:H:O films which in turn depends on the experimental conditions and the working gas mixture. Adjustable film properties were mainly attained using a pure DMC plasma considering both gas phase and surface processes. It is thus possible to prepare C:H:O PPFs with controllable degradability both in air and in water.

Fiber Surface Modification; Characterization of Rattan Fiber Reinforced Composite

Increasing the awareness of global warming and the depletion of petroleum resources had made many researchers focuses on using natural materials such as rattan. Its an edible fibers are prepared to reinforce matrix yielding composite products within the aid of epoxy based resin and hardener which also perform as catalyst. The fibres are previously conducted an alkali treatment, this was considered to enhance the cohessiveness of fibers to matrix. Silane and dimethylethanolamine (DMEA) as an adhesives booster is respectively added to the composite formula. The specific purpose of this research is to know the influence of addition of Silane and DMEA to the final properties of composite; flexural, tensile strength, elongation at break, hardness, and thermal. From the test results it is found that Silane keeps the matrix amorphous, while the addition of DMEA formed crystalline polymer. The ultimate property of the composites are found also depends on fiber woven pattern.

Experimental and micromechanical modeling of fracture toughness: MWCNT-reinforced polypropylene/glass fiber hybrid composites

In this study, polypropylene-based nano and hybrid composites are prepared with 20 wt% glass fiber and multiwalled carbon nanotubes (MWCNTs) ranging up to 5 wt%. The multiaxial stress fields developed during external loading of composites cause crack propagation by various fracture mechanisms. Among the nanocomposites, it is observed that the critical stress intensity factor (KI) is highest for the one prepared at 3 wt% loading of MWCNTs. The synergistic effect of multiscale fillers in hybrid composite with MWCNT content of 3 wt% results in superior fracture toughness properties as evidenced by 16.6% increase in KI with respect to neat PP. Analytical expressions that take into account the fracture mechanisms like particle debonding and matrix yielding are employed to estimate the composite crack resistance and then compared with experimentally obtained fracture toughness properties. The fracture toughness properties are found to be dependent on composition of fillers, matrix yield strain, and debonding strain of the composites.

Fracture behavior of highly toughened poly(lactic acid)/ethylene-co-vinyl acetate blends

Poly(lactic acid) (PLA) is brittle which restricts the range of its applications. The toughness of PLA was effectively improved in this work by incorporation of rubber grade ethylene-co-vinyl acetate (EVM). For example, the elongation at break of PLA increased by about 50 times after the addition of the EVM (10–30 wt%), although the EVM was not miscible with the PLA matrix. Furthermore, the notched impact toughness of PLA/EVM blend (70/30 wt/wt) reached to 85 kJ/m2 even at a temperature as low as −10°C. The critical temperatures of brittle-to-ductile transition (BDT) for PLA/EVM blends are observed at −20~0°C depending on the composition, while no BTD transition appeared for neat PLA. The impact fracture surface morphology of PLA and PLA/EVM blends observed by SEM indicates that the toughening modification was achieved through obvious matrix yielding. Moreover, the toughening behavior of the PLA/EVM blends was also interpreted quantitatively by using a single-edge notched three-point bending model (SEN3PB). The SEN3PB experiments reveal that the fracture energy was consumed in an outer plastic zone away from the fracture surface rather than in the inner fracture process zone, which accounts for the high toughness of the PLA/EVM blends.

Squalene/polyethylenimine based non-viral vectors: synthesis and use in systems for sustained gene release

New squalene/BPEI conjugates, acting as efficient gene carriers, were included in the 3D matrix, yielding tunable DNA release and long-term bioavailability.

Dynamic effects of a single fiber break in unidirectional glass fiber-reinforced polymer composites: Effects of matrix plasticity

In a unidirectional composite under static tensile loading, breaking of a fiber is shown to be a locally dynamic process, leading to stress concentrations in the matrix and neighboring fibers and debonding of the interface, which can propagate at high speed over long distances. In our previous work, a fiber break within a two-dimensional fiber array embedded in elastic epoxy matrix (with cohesive interface) was modeled to quantify the effects of these dynamic stresses. The results indicated that the elastic limit of the polymer matrix can be exceeded. In this study, the effects of matrix plasticity on dynamic stress concentrations due to a single fiber break are investigated. For the range of matrix yield stresses considered, the dynamic stress concentrations are significantly higher than corresponding values predicted by a quasi-static model with a pre-broken fiber. Based on the ratio of shear yield strength of the matrix and mode II peak traction of the interface cohesive law, two distinct regimes of damage are shown to exist. Only matrix yielding occurs when this ratio is less than 1.0, while both interfacial debonding and matrix yielding occur when it is greater than 1.0. At higher fiber break strengths, where the elastic matrix model predicts unstable interfacial debonding, reduction in matrix yield strength leads to a transition to stable debonding and arrest. Reducing the matrix yield strength also leads to a lowering of the peak dynamic stress concentrations in adjacent fibers, while spreading the stress concentrations over a larger volume of the composite microstructure.