In the current shift from conventional fossil-fuel-based materials to renewable energy, ecofriendly materials have attracted extensive research interest due to their sustainability and biodegradable properties. The integration of sustainable materials in electronics provides industrial benefits from wasted bio-origin resources and preserves the environment. This review covers the use of sustainable materials as components in organic electronics, such as substrates, insulators, semiconductors, and conductors. We hope this review will stimulate interest in the potential and practical applications of sustainable materials for green and sustainable industry.
In the past decades, ion conductive polymers and elastomers have drawn worldwide attention for their advanced functions in batteries, electroactive soft robotics, and sensors. Stretchable ionic elastomers with dispersed soft ionic moieties such as ionic liquids have gained remarkable attention as soft sensors, in applications such as the wearable devices that are often called electric skins. A considerable amount of research has been done on ionic-elastomer-based strain, pressure, and shear sensors; however, to the best of our knowledge, this research has not yet been reviewed. In this review, we summarize the materials and performance properties of engineered ionic elastomer actuators and sensors. First, we review three classes of ionic elastomer actuators—namely, ionic polymer metal composites, ionic conducting polymers, and ionic polymer/carbon nanocomposites—and provide perspectives for future actuators, such as adaptive four-dimensional (4D) printed systems and ionic liquid crystal elastomers (iLCEs). Next, we review the state of the art of ionic elastomeric strain and pressure sensors. We also discuss future wearable strain sensors for biomechanical applications and sports performance tracking. Finally, we present the preliminary results of iLCE sensors based on flexoelectric signals and their amplification by integrating them with organic electrochemical transistors.
Host–guest molecular recognition at the liquid–liquid interface endows the interface with unique properties, including stimuli-responsiveness and self-regulation, due to the dynamic and reversible nature of non-covalent interactions. Increasing research efforts have been put into the preparation of supramolecular interfacial systems such as films and microcapsules by integrating functional components (e.g., colloidal particles, polymers) at the interface, providing tremendous opportunities in the areas of encapsulation, delivery vehicles, and biphasic reaction systems. In this review, we summarize recent progress in supramolecular interfacial systems assembled by host–guest chemistry, and provide an overview of the fabrication process, functions, and promising applications of the resultant constructs.
Lightweight and mechanically strong natural silk fibers have been extensively investigated over the past decades. Inspired by this research, many artificial spinning techniques (wet spinning, dry spinning, electrospinning, etc.) have been developed to fabricate robust protein fibers. As the traditional spinning methods provide poor control over the as-spun fibers, microfluidics has been integrated with these techniques to allow the fabrication of biological fibers in a well-designed manner, with simplicity and cost efficiency. The mechanical behavior of the developed fibers can be precisely modulated by controlling the type and size of microfluidic channel, flow rate, and shear force. This technique has been successfully used to manufacture a broad range of protein fibers, and can accelerate the production and application of protein fibers in various fields. This review outlines recent progress in the design and fabrication of protein-based fibers based on microfluidics. We first briefly discuss the natural spider silk-spinning process and the microfluidics spinning process. Next, the fabrication and mechanical properties of regenerated protein fibers via microfluidics are discussed, followed by a discussion of recombinant protein fibers. Other sourced protein fibers are also reviewed in detail. Finally, a brief outlook on the development of microfluidic technology for producing protein fibers is presented.
A plastic may degrade in response to a trigger. The kinetics of degradation have long been characterized by the loss of weight and strength over time. These methods of gross characterization, however, are misleading when plastic degrades heterogeneously. Here, we study heterogeneous degradation in an extreme form: the growth of a crack under the combined action of chemistry and mechanics. An applied load opens the crack, exposes the crack front to chemical attack, and causes the crack to outrun gross degradation. We studied the crack growth in polylactic acid (PLA), a polyester in which ester bonds break by hydrolysis. We cut a crack in a PLA film using scissors, tore it using an apparatus, and recorded the crack growth using a camera through a microscope. In our testing range, the crack velocity was insensitive to load but was sensitive to humidity and pH. These findings will aid the development of degradable plastics for healthcare and sustainability.
Nanobubbles have attracted considerable attention in various industrial applications due to their exceptionally long lifetime and their potential as carriers at the nanoscale. The stability and physiochemical properties of nanobubbles are highly sensitive to the presence of surfactants that can lower their surface tension or improve their electrostatic stabilization. Herein, we report real-time observations of the dynamic behaviors of nanobubbles in the presence of soluble surfactants. Using liquid-phase transmission electron microscopy (TEM) with multi-chamber graphene liquid cells, bulk nanobubbles and surface nanobubbles were observed in the same imaging condition. Our direct observations of nanobubbles indicate that stable gas transport frequently occurs without interfaces merging, while a narrow distance is maintained between the interfaces of interacting surfactant-laden nanobubbles. Our results also elucidate that the interface curvature of nanobubbles is an important factor that determines their interfacial stability.
A novel method has been successfully developed for the facile and efficient removal of organic micropollutants (OMP) from water based on novel functional capsules encapsulating molecular-recognizable nanogels. The functional capsules are composed of ultrathin calcium alginate (Ca-Alg) hydrogel shells as semipermeable membranes and encapsulated poly(N-isopropylacrylamide-co-acrylic acid-g-mono-
(6-ethanediamine-6-deoxy)-β-cyclodextrin) (PNCD) nanogels with β-cyclodextrin (CD) moieties as OMP capturers. The semipermeable membranes of the capsules enable the free transfer of OMP and water molecules across the capsule shells, but confine the encapsulated PNCD nanogels within the capsules. Bisphenol A (BPA), an endocrine-disrupting chemical that is released from many plastic water containers, was chosen as a model OMP molecule in this study. Based on the host–guest recognition complexation, the CD moieties in the PNCD nanogels can efficiently capture BPA molecules. Thus, the facile and efficient removal of BPA from water can be achieved by immersing the proposed functional capsules into BPAcontaining aqueous solutions and then simply removing them, which is easily done due to the capsules' characteristically large size of up to several millimeters. The kinetics of adsorption of BPA molecules by the capsules is well described by a pseudo-second-order kinetic model, and the isothermal adsorption thermodynamics align well with the Freundlich and Langmuir isothermal adsorption models. The regeneration of capsules can be achieved simply by washing them with water at temperatures above the volume phase transition temperature of the PNCD nanogels. Thus, the proposed functional capsules encapsulating molecular-recognizable nanogels provide a novel strategy for the facile and efficient removal of OMP from water.
Engineering the electrical properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) holds great potential for various applications such as sensors, thermoelectric (TE) generators, and hole transport layers in solar cells. Various strategies have been applied to achieve optimal electrical properties, including base solution post-treatments. However, the working mechanism and the exact details of the structural transformations induced by base post-treatments are still unclear. In this work, we present a comparative study on the post-treatment effects of using three common and green alkali base solutions: namely LiOH, NaOH, and KOH. The structural modifications induced in the film by the base post-treatments are studied by techniques including atomic force microscopy, grazingincidence
wide-angle X-ray scattering, ultraviolet–visible–near-infrared spectroscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy. Base-induced structural modifications are responsible for an improvement in the TE power factor of the films, which depends on the basic solution used. The results are explained on the basis of the different affinity between the alkali cations and the PSS chains, which determines PEDOT dedoping. The results presented here shed light on the structural reorganization occurring in PEDOT:PSS when exposed to high-pH solutions and may serve as inspiration to create future pH-/ion-responsive devices for various applications.
Flow profiles are frequently engineered in microfluidic channels for enhanced mixing, reaction control, and material synthesis. Conventionally, flow profiles are engineered by inducing inertial secondary flow to redistribute the streams, which can hardly be reproduced in microfluidic environments with negligible inertial flow. The employed symmetric channel structures also limit the variety of achievable flow profiles. Moreover, each of the flow profiles specifically corresponds to a strictly defined flow condition and cannot be generalized to other flow environments. To address these issues, we present a systematic method to engineer the flow profile using inertialess secondary flow. The flow is manipulated in the Stokes regime by deploying a cascaded series of microsteps with various morphologies inside a microchannel to shape the flow profile. By tuning the shapes of the microsteps, arbitrary outflow profiles can be customized. A numerical profile-transformation program is developed for rapid prediction of the output profiles of arbitrary sequences of predefined microsteps. The proposed method allows the engineering of stable flow profiles, including asymmetric ones, over a wide range of flow conditions for complex microfluidic environmental prediction and design.
Carbohydrates, which are mostly present in sugar, starch, and fiber, are one of the main ingredients of food and the primary source of energy in the human diet. Among these three main sources, starch stands out as one of the most abundant reserves of carbohydrates. Investigating starch would not only enhance our understanding of the functionality of starch in the human body but also aid in the design of novel starch-based dietary foods. The present review first provides a state-of-the-art understanding of the various classifications of dietary starches, including rapidly digesting starch (RDS), slowly digesting starch (SDS), and resistant starch (RS). Moreover, both the in vivo and in vitro determination methods of the digestibility of starch-based dietary foods are discussed. Based on the current understanding, present research strategies to design novel starch-based dietary foods through either the direct addition of modified starch or the alteration of processing conditions are highlighted. Furthermore, certain perspectives related to the future research directions of starch-based foods are also included.
Rapid global population growth has caused an increasing need for products containing protein. Meat products are the most common high-protein food source, but impact the environment, cause animal welfare issues, and raise public health concerns. Consumer health and food safety are paramount to the food industry. Both the scientists and food industry are actively seeking plant proteins to substitute for animal-sourced proteins. Plant proteins have a well-balanced amino acid composition, and exhibit great potential for replacing meat via the development of healthy, high-protein, low-saturated fat, cholesterolfree, and nutritionally similar meat-like products. Generally, meat analogue formulations are specially designed and processing conditions are optimized to obtain the texture and bite of real animal meat. This article focuses on plant-based meat analogues, and covers aspects regarding processing, products, quality, and nutritional and structural modifications. Product safety consciousness and consumer acceptance are also discussed. Challenges and perspectives for future research concerning nonmeat products are presented.
Non-alcoholic fatty liver disease (NAFLD), which has a global prevalence of 20%–33%, has become the main cause of chronic liver disease. Except for lifestyle medication, no definitive medical treatment has been established so far, making it urgent to find effective strategies for the treatment of NAFLD. With the identification of the significant role played by the gut microbiota in the pathogenesis of NAFLD, studies on probiotics for the prevention and treatment of NAFLD are increasing in number. Bacteria from the Bifidobacterium and Lactobacillus genera constitute the most widely used traditional probiotics. More recently, emerging next-generation probiotics (NGPs) such as Akkermansia muciniphila and Faecalibacterium prausnitzii have also gained attention due to their potential as therapeutic options for the treatment of NAFLD. This review provides an overview of the effects of oral administration of traditional probiotics and NGPs on the development and progress of NAFLD. The mechanisms by which probiotics directly or indirectly affect the disease are illustrated, based on the most recent animal and clinical studies. Although numerous studies have been published on this topic, further research is required to comprehensively understand the specific underlying mechanisms among probiotics, gut microbiota, and NAFLD, and additional large-scale clinical trials are required to evaluate the therapeutic efficacy of probiotics for the treatment of NAFLD, as well as the safety of probiotics in the human body.
Fault is a common geological structure that has been revealed in the process of underground coal excavation and mining. The nature of its discontinuous structure controls the deformation, damage, and mechanics of the coal or rock mass. The interaction between this discontinuous structure and mining activities is a key factor that dominates fault reactivation and the coal burst it can induce. This paper first summarizes investigations into the relationships between coal mining layouts and fault occurrences, along with relevant conceptual models for fault reactivation. Subsequently, it proposes mechanisms of fault reactivation and its induced coal burst based on the superposition of static and dynamic stresses, which include two kinds of fault reactivations from: mining-induced quasi-static stress (FRMSS)-dominated and seismic-based dynamic stress (FRSDS)-dominated. These two kinds of fault reactivations are then validated by the results of experimental investigations, numerical modeling, and in situ microseismic monitoring. On this basis, monitoring methods and prevention strategies for fault-induced coal burst are discussed and recommended. The results show that fault-induced coal burst is triggered by the superposition of high static stress in the fault pillar and dynamic stress from fault reactivation. High static stress comes from the interaction of the fault and the roof structure, and dynamic stress can be ascribed to FRMSS and FRSDS. The results in this paper could be of great significance in guiding the monitoring and prevention of fault-induced coal bursts.