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Increasing environmental concerns raised by the accumulation of electronic waste draws attention to the development of sustainable materials for short‐lived electronics. In this framework, printed capacitive humidity sensors and temperature resistive detectors composed exclusively of biodegradable materials: shellac, carbon‐derived particles, and egg‐albumin are reported. The sensor platform comprises interdigitated electrodes serving as a capacitive transducer for humidity sensing, and a serpentine used as a resistive temperature detector. Both the interdigitated and serpentine electrodes are manufactured by screen‐printing carbon ink on a shellac substrate. The humidity sensors are constructed by drop‐coating egg albumin on the interdigitated carbon electrodes and the temperature detector is prepared by encapsulating the serpentine design with shellac. Shellac is shown to be a biodegradable alternative to hydrophilic cellulose‐derived substrates, with the capacitive humidity sensors demonstrating a sensitivity of 0.011% RH−1. The response and recovery times on shellac are 12 and 20 times faster than on cellulose‐based substrate, and the serpentine resistive temperature detectors have a temperature coefficient of 5300 ppm K−1. At the end of their service‐life, the sensors produced are home compostable and can be environmentally friendly disposed, potentially enabling their future use for sustainable and environmentally friendly smart‐packaging, agricultural sensing, or point‐of‐care testing. [ABSTRACT FROM AUTHOR]

Organohydrogel‐based strain sensors have gained increasing attention in the fields of real‐time healthcare and motion detection due to their excellent flexibility, stretchability, and skin‐like compliance. However, the fundamental attributes, such as mechanical elasticity, self‐adhesiveness, and biocompatibility, are challenging to be simultaneously obtained in organohydrogels, limiting their applications in wearable electronics. Additionally, traditional organohydrogels need to be fixed to the surface of the human skin and suffer from inferior breathability, resulting in complicated operations and severe uncomfortableness, respectively. Herein, a multifunctional organohydrogel is designed for wearable strain sensor by a facile digital light processing (DLP) 3D printing technology. By rationally tailoring the chemical (poly(N‐acryloylmorpholine)/poly(ethylene glycol) diacrylate) and physical (poly(N‐acryloylmorpholine)/poly(ethylene glycol) diacrylate and glycerin/water) cross‐linking networks, the organohydrogel exhibits promising water absorption/retention, high stretchability, impressive elasticity, and promising fatigue resistance. Additionally, good ionic conductivity, inherent self‐adhesiveness, and biocompatibility are simultaneously achieved. On the basis of the multifunctionalities, 3D multihole organohydrogels are designated as wearable and breathable strain sensors, facilitating the manipulation without any fixation and increasing the wear comfortableness. It is believed that 3D printed multihole organohydrogels show great potential in wearable flexible electronics. [ABSTRACT FROM AUTHOR]

Food security is critical for the sustainability of society. The spoilage of stocked food is an ongoing problem that causes significant losses to the global economy. Novel portable analytical platforms that provide timely information on the condition of food stock can support informed decision‐making on the safety of food consumption as well as on maximization of food storage lifetime. Ammonia (NH3) and hydrogen sulfide (H2S) are two of the major harmful gases that are produced due to bacteria activity during the food spoilage process. The timely detection of these gases in food stocks has vital importance to human health. In this review article, the recent progress of conducting polymer based NH3 and H2S gas sensors including sensor device prototypes, their sensing mechanisms, materials and methodologies for sensor fabrication, and their suitability for the development of consumer electronic devices for food spoilage detection are highlighted. [ABSTRACT FROM AUTHOR]

Superamphiphobic coatings that simultaneously repel both water and oil and are applicable to a wide range of surfaces are needed for use in self‐cleaning, anti‐icing, and antimicrobial coatings. Spray coating is a method that can be used to apply such coatings to a wide range of surfaces in a scalable and high throughput manner. This review presents a comprehensive overview of the materials architecture, synthesis, applications, and figures‐of‐merit of superamphiphobic surfaces that are deposited using spray coating. The design requirements of superamphiphobic surfaces—surface roughness and wettability, re‐entrant topographic features, and chemical composition—are initially introduced. Based on the material, different synthesis techniques are then discussed with a focus on metal oxides and metal oxide composites, polymers, emerging, and green materials. The areas of application of superamphiphobic coatings are also presented. Finally, the main hurdles in using such coatings in real‐life applications are discussed in depth, and emerging technologies for overcoming these challenges are presented. [ABSTRACT FROM AUTHOR]

Although controlled wrinkling is demonstrated to be a powerful tool for micro/nanofabrication, large‐area fabrication of microarchitecture arrays on curved substrates by surface wrinkling still remains challenging. Inspired by the cortical folding, a facile method for transforming graphene oxide (GO) patterns into multiscale microarchitecture arrays on curved substrates is developed. Mass production of hierarchical GO papillae arrays can be realized by homogeneous compression of patterned GO/rubber bilayers. The reduced GO (rGO) papillae arrays show superhydrophobicity with tunable adhesion to water, enabling good performance in microdroplet manipulation. Besides, the papillae are capable of regulating the formation of microcracks in the rGO films upon stretching. Similar to the mechanical sensing system of spiders, a crack‐based strain sensor with high gauge factor (≈81), good linearity (0–15%), and fast responding speed (<40 ms) is demonstrated. In addition, the strain sensor is capable of detecting and recognizing multiple deformation modes including stretching, poking, and touching. This work reveals novel cortical folding morphology and provides a simple fabrication method for multifunctional hierarchical microarchitectures on curved substrates, which may find applications in biomimetic microstructures, smart wetting surfaces, and wearable electronics. [ABSTRACT FROM AUTHOR]

Due to their large contact and loading surfaces as well as high sensitivities to chemical changes, graphene‐based materials (GBMs) are increasingly being employed into novel nanomedicine technologies. Here biomolecule—monolayer graphene—kidney tissue hybrid structures are studied using mapping micro‐Raman and fluorescence spectroscopies. Because in this configuration graphene interacts with molecules on both sides, a double‐sided graphene‐enhanced Raman scattering (GERS) effect up to ≈10.1 is found for biomolecules adsorbed on graphene and amino acids in the kidney tissue below graphene. Moreover, graphene causes an efficient autofluorescence quenching (FLQ) up to ≈20% emitted by the kidney tissue. Despite the complexity of such layered materials, the intriguing simultaneous occurrence of double‐sided GERS (a new development of GERS) and FLQ phenomena can be well explained by suitable molecular structure and energy level alignment between molecules and graphene. These result in effective charge transfer mediated by non‐covalent interactions as indicated by correlative strain, doping, and defect analyses in graphene based on the Raman data and energy level calculations. Last, the advantages of using graphene over standard photobleaching are demonstrated. This work can be extended to other macromolecular entities toward integrating GBMs in versatile drug delivery, imaging, and sensing devices. [ABSTRACT FROM AUTHOR]

Cell‐repellent interfaces have various applications, including microfluidic devices, biosensors, and antibiofouling surfaces. Efficient cell repellency, long‐term stability, and ability to fabricate micropatterns with cell repellency are main optimal requirements for cell‐repellent interfaces. In this study, a flexible and practical method is proposed to construct a cell‐repellent interface and engineer controlled cell organization. Using femtosecond‐laser direct writing to pattern surfaces with microcraters, it is shown that micropatterned surfaces with physical and chemical changes have outstanding characteristics of super‐hydrophobicity. Furthermore, the cell adhesion is inhibited by these features and arbitrary cell patterns are achieved by selective cell adhesion induced by the distribution of the microcrater structures. These findings suggest a high potential for directing cell organization with desired shapes to analyze the fundamental mechanism of cell adhesion. [ABSTRACT FROM AUTHOR]

Food sensors have been developed for quality monitoring and contaminant detection to improve food management. Despite the alarming rates of food waste and food‐related illness, few food sensor technologies are utilized and translated into commercial products. This review aims to explore challenges and opportunities relating to sensor translation by first documenting recent advances in state‐of‐the‐art optical and electronic food sensors that target common analytes including temperature, humidity, pH, gases, pesticides, and pathogens. Promising sensors are designed with careful consideration of the chemistry of the contaminant or quality marker which they detect and the inherent challenges of analyte recognition in complex food samples. Recent advances focus on the incorporation of sensors into materials and devices for food packaging and processing. Challenges and opportunities for food sensor translation are then identified and discussed including the complexity of and natural variation in food products, different causes of food spoilage, the food–sensor interface, signal processing and governing legislation. For the successful translation of sensors into ubiquitous features on food products, these issues must be addressed through material and design advances. [ABSTRACT FROM AUTHOR]

Hydrogels, which are hydrophilic soft porous networks, are an important class of materials of broad relevance to bioanalytical chemistry, soft‐robotics, drug delivery, and regenerative medicine. Transformer hydrogels are micro‐ and mesostructured hydrogels that display a dramatic transformation of shape, form, or dimension with associated changes in function, due to engineered local variations such as in swelling or stiffness, in response to external controls or environmental stimuli. This review describes principles that can be utilized to fabricate transformer hydrogels such as by layering, patterning, or generating anisotropy, and gradients. Transformer hydrogels are classified based on their responsivity to different stimuli such as temperature, electromagnetic fields, chemicals, and biomolecules. A survey of the current research progress suggests applications of transformer hydrogels in biomimetics, soft robotics, microfluidics, tissue engineering, drug delivery, surgery, and biomedical engineering. [ABSTRACT FROM AUTHOR]

Human skin, the largest organ of human body, can perceive tactile sensations, temperature, humidity, and other complex environmental stimulations. To mimic the capabilities of human skin, graphene provides great potential in building wearable electronic skins (E‐skins), which hold broad applications in advanced robotics, healthcare monitoring, artificial intelligence, human–machine interfaces, etc. Herein, the recent progress in flexible tactile sensors and E‐skins based on graphene material is presented. A brief introduction of the main approaches to prepare graphene nanosheets is provided. The main developments on the functions and mechanisms of bionic functional devices in E‐skins including tactile sensors, temperature sensors, and humidity sensors are then highlighted. The current and future applications for graphene‐based E‐skins, such as multifunctional biomimetic E‐skins, healthcare monitoring, and interactive human–machine interface, are also described. Finally, the existing challenges and future development trends for graphene‐based E‐skins are discussed. Graphene‐based electronic skins (E‐skins) hold great significant for building wearable and portable devices, which can precisely perceive tactile, temperature, and humidity, etc. An overview on this field is given, summarizing the recent researches and application perspectives of graphene‐based tactile sensors and E‐skins. [ABSTRACT FROM AUTHOR]