Ethylene is a hormone that plays a critical role in many phases of plant growth and fruit ripening. Currently, detection of ethylene heavily relies on sophisticated and timeconsuming conventional assays such as chromatography, spectroscopy, and electrochemical methods. Herein, we develop a polydiacetylene-based sensor for the detection of ethylene via color change. The sensors are prepared through the reaction between polydiacetylene and Lawesson's reagent that results in decorating polydiacetylene with terminal thiol groups. Upon exposure to ethylene, the sensor changes color from blue to red which is visible to the naked eye. Our device shows a limit of detection for ethylene at 600 ppm in air and can be applied for monitoring ethylene released during the fruit-ripening process. Such easy-to-use ethylene sensors may find applications in plant biology, agriculture, and food industry.

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Lignin is a low-cost, natural polymer with abundant polar sites on its backbone that can be utilized for physical cross-linking of polymers. Here, we use lignin for additional cross-linking of hydrophilic polyether-based polyurethane (HPU) hydrogels, aiming to improve their mechanical properties and processability. Without reducing the swelling, simple addition of 2.5 wt % lignin increases the fracture energy and Young's modulus of HPU hydrogels from, respectively, 1540 ± 40 to 2050 ± 50 J m −2 and 1.29 ± 0.06 to 2.62 ± 0.84 MPa. Lignin also increases the lap shear adhesiveness of hydrogels and induces an immediate load recovery of 95%. We further confirm that hydrogen bonding is the dominant toughening mechanism and elucidate the toughening mechanism by applying the Lake-Thomas and a recently developed sequential debonding theory. We show that unlike the Lake−Thomas theory, the latter model is able to capture the impact of lignin on toughening of hydrogels. Moreover, the lignin-loaded HPU hydrogels are easily processable by various techniques, such as fiber spinning, casting, and 3D printing and are biocompatible with primary human dermal fibroblasts.

To determine the most appropriate use of lignin, surface, structural, and thermal characteristics of lignin was investigated in this work. It was observed that kraft lignin (KL), the lignin of prehydrolysis liquor (LPHL), lignosulfonate of NSSC process (LSL), and lignosulfonates (LSs) of sulfite pulping process had 0.67, 0.25, 0.90, and 1.52-2.25 meq/g anionic charge density, and 6.3, 2.1, 10.1, and 8.8-10.1 nm hydrodynamic diameter, respectively. These results suggested that LSL and LSs could be used more effectively than other lignin as filler modifiers, flocculants, and dispersants. The combustion studies of the lignin samples suggested that KL and LPHL combusted more efficiently than other samples, as they had high heating (calorific) values of 27.02 and 19.2 MJ/kg, the apparent activation energy of 126.64 and 99.14 kJ/mol based on Flynn-Wall-Ozawa method and 122.16 and 94.73 kJ/mol based on Kissinger-Akahira-Sunose and no ash, respectively. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42336.

Wood chips are pretreated with steam prior to refining in the thermomechanical pulping process. The steam treatment dissolves part of lignin of wood chips in the spent liquor (SL) of this process, and subsequently the SL is sent to the wastewater system of the process. However, the lignin of SL can be used in the production of value-added chemicals, but it should first be separated from the SL in order to have a feasible downstream process. In this study, activated carbon (AC) was considered as an adsorbent to isolate lignin from SL. The results showed that the maximum adsorption of lignin on AC was 166 mg/g under the optimal conditions of pH 5.2, 30 degrees C and 3 h treatment. Furthermore, the separation of lignin from SL was improved from 45% to 60% by having a two-stage adsorption process at pH 5.2, which also reduced the turbidity and chemical oxygen demand of SL by 39% and 32%, respectively.

Hydrogen peroxide (H2O2) is a common chemical used in many industries and can be found in various biological environments, water, and air. Yet, H2O2 in a certain range of concentrations can be hazardous and toxic. Therefore, it is crucial to determine its concentration at different conditions for safety and diagnostic purposes. This review provides an insight about different types of sensors that have been developed for detection of H2O2. Their flexibility, stability, cost, detection limit, manufacturing, and challenges in their applications have been compared. More specifically the advantages and disadvantages of various flexible substrates that have been utilized for the design of H2O2 sensors were discussed. These substrates include carbonaceous substrates (e.g., reduced graphene oxide films, carbon cloth, carbon, and graphene fibers), polymeric substrates, paper, thin glass, and silicon wafers. Many of these substrates are often decorated with nanostructures composed of Pt, Au, Ag, MnO2, Fe3O4, or a conductive polymer to enhance the performance of sensors. The impact of these nanostructures on the sensing performance of resulting flexible H2O2 sensors has been reviewed in detail. In summary, the detection limits of these sensors are within the range of 100 nM–1 mM, which makes them potentially, but not necessarily, suitable for applications in health, food, and environmental monitoring. However, the required sample volume, cost, ease of manufacturing, and stability are often neglected compared to other detection parameters, which hinders sensors’ real-world application. Future perspectives on how to address some of the substrate limitations and examples of application-driven sensors are also discussed.

devices, [5,6] textiles, [7] bionics, [8,9] soft electronics, [10] and soft robotic [11] systems. Yet, the majority of methods developed for manufacturing flexible sensors are cumbersome, inconvenient, and often expensive. For instance, rigid materials can be made flexible once their thickness is reduced to micrometer or nanometer scales through specialized fabrication methods. [12,13] Nanostructured semiconductors such as graphene, [14] nontransition-metal oxides such as ZnO, SnO 2 , Ga 2 O 3 , [15,16] and transition metal dichalcogenides [17] are a few examples of materials used for micro/nanofabrication of sensors. However, these materials are still intrinsically rigid, and complex fabrication techniques are required to create substrates thin enough to become flexible.Amongst the numerous sensors integrated into our modern lifestyle, pH sensors are amongst the most common. pH is considered a fundamental environmental signal that provides considerable information about the surrounding environment. Representing the proton activity of the solution, pH can be directly linked to other environmental signals such as the level of CO 2 in aqueous solutions or the activity of certain biological species. [18] Traditionally, pH is measured electrochemically or spectrometrically. Both methods are based on materials that are rigid and incompatible with flexible systems. A few flexible pH sensors have been developed based on ion-sensitive flexible electrodes in which the change in the potential of a working electrode against a reference electrode is used as a measure of pH. Early examples of such ion-sensitive pH sensors were made by embedding hydrogen ionophore species in the plasticized poly(vinyl chloride) (PVC) laminated on a polyimide (PI) substrate. [19,20] While the researchers were able to demonstrate the ionic sensitivity of these sensors successfully, delamination of PVC from the substrate compromised the performance of the first generation of ion-sensitive sensors. Later, Koncki and Mascini utilized screen printing to deposit ruthenium oxide films as a proton sensitive layer on polyester films to fabricate flexible pH sensors. [21] Moreover, Huang et al. developed a flexible pH sensor by depositing iridium oxide on a PI substrate. [22] The potential application of such sensors in measuring pH in biological environments has been demonstrated for a live pig's oesophagus [23] as well as human and rabbit hearts. [24] Despite these technological advancements, the stiffness of materials used in these examples is considerably higher than that of biological tissues.In this study, we demonstrated an elegant approach for 3D printing of highly flexible pH-sensitive hydrogels based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with Current sensors for monitoring environmental signals, such as pH, are often made from rigid materials that are incompatible with soft biological tissues. The high stiffness of such materials sets practical limitations on the in situ utilization of sensors under biological conditions. This artic...

Native arteries contain a distinctive intima‐media composed of organized elastin and an adventitia containing mature collagen fibrils. In contrast, implanted biodegradable small‐diameter vascular grafts do not present spatially regenerated, organized elastin. The elastin‐containing structures within the intima‐media region encompass the elastic lamellae (EL) and internal elastic lamina (IEL) and are crucial for normal arterial function. Here, the development of a novel electrospun small‐diameter vascular graft that facilitates de novo formation of a structurally appropriate elastin‐containing intima‐media region following implantation is described. The graft comprises a non‐porous microstructure characterized by tropoelastin fibers that are embedded in a PGS matrix. After implantation in mouse abdominal aorta, the graft develops distinct cell and extracellular matrix profiles that approximate the native adventitia and intima‐media by 8 weeks. Within the newly formed intima‐media region there are circumferentially aligned smooth muscle cell layers that alternate with multiple EL similar to that found in the arterial wall. By 8 months, the developed adventitia region contains mature collagen fibrils and the neoartery presents a distinct IEL with thickness comparable to that in mouse abdominal aorta. It is proposed that this new class of material can generate the critically required, organized elastin needed for arterial regeneration.