Sustainable Natural Bio-Origin Materials for Future Flexible Devices

Flexible devices serve as important intelligent interfaces in various applications involving health monitoring, biomedical therapies, and human-machine interfacing. To address the concern of electronic waste caused by the increasing usage of electronic devices based on synthetic polymers, bio-origin materials that possess environmental benignity as well as sustainability offer new opportunities for constructing flexible electronic devices with higher safety and environmental adaptivity. Herein, the bio-source and unique molecular structures of various types of natural bio-origin materials are briefly introduced. Their properties and processing technologies are systematically summarized. Then, the recent progress of these materials for constructing emerging intelligent flexible electronic devices including energy harvesters, energy storage devices, and sensors are introduced. Furthermore, the applications of these flexible electronic devices including biomedical implants, artificial e-skin, and environmental monitoring are summarized. Finally, future challenges and prospects for developing high-performance bio-origin material-based flexible devices are discussed. This review aims to provide a comprehensive and systematic summary of the latest advances in the natural bio-origin material-based flexible devices, which is expected to offer inspirations for exploitation of green flexible electronics, bridging the gap in future human-machine-environment interactions.

Research on a Health Care Personnel Training Model Based on Multilayered Knowledge Mapping for the Integration of Nursing Courses and Examinations

While nursing courses provide a convenient and quick way to learn, they can also be overloaded with resources that can cause learners to become cognitively disoriented or have difficulty choosing nursing course. This paper proposes to fully explore learners' interests in the case of sparse data by fusing knowledge graph technology and deep recommendation models and adopt knowledge graph to model nursing courses at the semantic level so as to correspond the set of nursing courses to the knowledge graph and solve the problem of lack of logical knowledge relationships. Due to the specificity of its positions, the nursing profession must accurately position the nursing professional curriculum standards in the process of determining the talent cultivation model based on the nursing professional positions and the admission requirements for nursing practice qualification. Through linear feature mining based on the knowledge graph, entities and relationships are used to intuitively display the interest paths of nursing professional learners and enhance the interpretability of recommendations.

Silk Fibroin and Pomegranate By-Products to Develop Sustainable Active Pad for Food Packaging Applications

In this study, a bio-based polymeric system loaded with fruit by-products was developed. It was based on silk fibroin produced by the silkworm Bombyx mori and pomegranate peel powder, selected as active agent. The weight ratio between fibroin and pomegranate powder was 30:70. Pads also contained 20% w/w of glycerol vs. fibroin to induce water insolubility. Control systems, consisting of only fibroin and glycerol, were produced as reference. Both control and active systems were characterized for structural and morphological characterization (Fourier-transform infrared spectroscopy and optical microscope), antioxidant properties and antimicrobial activity against two foodborne spoilage microorganisms. Results demonstrate that under investigated conditions, an active system was obtained. The pad showed a good water stability, with weight loss of about 28% due to the release of the active agent and not to the fibroin loss. In addition, this edible system has interesting antioxidant and antimicrobial properties. In particular, the pad based on fibroin with pomegranate peel recorded an antioxidant activity of the same order of magnitude of that of vitamin C, which is one of the most well-known antioxidant compounds. As regards the antimicrobial properties, results underlined that pomegranate peel in the pad allowed maintaining microbial concentration around the same initial level (10⁴ CFU/mL) for more than 70 h of monitoring, compared to the control system where viable cell concentration increased very rapidly up to 10⁸ CFU/mL.

Glial Interfaces: Advanced Materials and Devices to Uncover the Role of Astroglial Cells in Brain Function and Dysfunction

Research over the past four decades has highlighted the importance of certain brain cells, called glial cells, and has moved the neurocentric vision of structure, function, and pathology of the nervous system toward a more holistic perspective. In this view, the demand for technologies that are able to target and both selectively monitor and control glial cells is emerging as a challenge across neuroscience, engineering, chemistry, and material science. Frequently neglected or marginally considered as a barrier to be overcome between neural implants and neuronal targets, glial cells, and in particular astrocytes, are increasingly considered as active players in determining the outcomes of device implantation. This review provides a concise overview not only of the previously established but also of the emerging physiological and pathological roles of astrocytes. It also critically discusses the most recent advances in biomaterial interfaces and devices that interact with glial cells and thus have enabled scientists to reach unprecedented insights into the role of astroglial cells in brain function and dysfunction. This work proposes glial interfaces and glial engineering as multidisciplinary fields that have the potential to enable significant advancement of knowledge surrounding cognitive function and acute and chronic neuropathologies.

Nanostructured Organic/Hybrid Materials and Components in Miniaturized Optical and Chemical Sensors

In the last decade, biochemical sensors have brought a disruptive breakthrough in analytical chemistry and microbiology due the advent of technologically advanced systems conceived to respond to specific applications. From the design of a multitude of different detection modalities, several classes of sensor have been developed over the years. However, to date they have been hardly used in point-of-care or in-field applications, where cost and portability are of primary concern. In the present review we report on the use of nanostructured organic and hybrid compounds in optoelectronic, electrochemical and plasmonic components as constituting elements of miniaturized and easy-to-integrate biochemical sensors. We show how the targeted design, synthesis and nanostructuring of organic and hybrid materials have enabled enormous progress not only in terms of modulation and optimization of the sensor capabilities and performance when used as active materials, but also in the architecture of the detection schemes when used as structural/packing components. With a particular focus on optoelectronic, chemical and plasmonic components for sensing, we highlight that the new concept of having highly-integrated architectures through a system-engineering approach may enable the full expression of the potential of the sensing systems in real-setting applications in terms of fast-response, high sensitivity and multiplexity at low-cost and ease of portability.

Side chain modification on PDI-spirobifluorene-based molecular acceptors and its impact on organic solar cell performances

N-Substitution in perylene diimide (PDI) n-type semiconductors is critical for their performance in organic bulk heterojunction solar cells.

Towards Efficient Spectral Converters through Materials Design for Luminescent Solar Devices

Single-junction photovoltaic devices exhibit a bottleneck in their efficiency due to incomplete or inefficient harvesting of photons in the low- or high-energy regions of the solar spectrum. Spectral converters can be used to convert solar photons into energies that are more effectively captured by the photovoltaic device through a photoluminescence process. Here, recent advances in the fields of luminescent solar concentration, luminescent downshifting, and upconversion are discussed. The focus is specifically on the role that materials science has to play in overcoming barriers in the optical performance in all spectral converters and on their successful integration with both established (e.g., c-Si, GaAs) and emerging (perovskite, organic, dye-sensitized) cell types. Current challenges and emerging research directions, which need to be addressed for the development of next-generation luminescent solar devices, are also discussed.

Metal nanoparticles triggered persistent negative photoconductivity in silk protein hydrogels

Silk protein is a natural biopolymer with intriguing properties, which are attractive for next generation bio-integrated electronic and photonic devices. Here, we demonstrate the negative photoconductive response of Bombyx mori silk protein fibroin hydrogels, triggered by Au nanoparticles. The room temperature electrical conductivity of Au-silk hydrogels is found to be enhanced with the incorporation of Au nanoparticles over the control sample, due to the increased charge transporting networks within the hydrogel. Au-silk lateral photoconductor devices show a unique negative photoconductive response under an illumination of 325 nm, with excitation energy higher than the characteristic metal plasmon resonance band. The enhanced photoconductance yield in the hydrogels over the silk protein is attributed to the photo-oxidation of amino groups in the β-pleated sheets of the silk around the Au nanoparticles followed by the breaking of charge transport networks. The Au-silk nanocomposite does not show any photoresponse under visible illumination because of the localization of excited charges in Au nanoparticles. The negative photoconductive response of hybrid Au-silk under UV illumination may pave the way towards the utilization of silk for future bio-photonic devices using metal nanoparticle platforms.

Enhanced Ultraviolet Stability of Air-Processed Polymer Solar Cells by Al Doping of the ZnO Interlayer

Photostability of organic photovoltaic devices represents a key requirement for the commercialization of this technology. In this field, ZnO is one of the most attractive materials employed as an electron transport layer, and the investigation of its photostability is of particular interest. Indeed, oxygen is known to chemisorb on ZnO and can be released upon UV illumination. Therefore, a deep analysis of the UV/oxygen effects on working devices is relevant for the industrial production where the coating processes take place in air and oxygen/ZnO contact cannot be avoided. Here we investigate the light-soaking stability of inverted organic solar cells in which four different solution-processed ZnO-based nanoparticles were used as electron transport layers: (i) pristine ZnO, (ii) 0.03 at %, (iii) 0.37 at %, and (iv) 0.8 at % aluminum-doped AZO nanoparticles. The degradation of solar cells under prolonged illumination (40 h under 1 sun), in which the ZnO/AZO layers were processed in air or inert atmosphere, is studied. We demonstrate that the presence of oxygen during the ZnO/AZO processing is crucial for the photostability of the resulting solar cell. While devices based on undoped ZnO were particularly affected by degradation, we found that using AZO nanoparticles the losses in performance, due to the presence of oxygen, were partially or totally prevented depending on the Al doping level.

Effect of different fabrication methods on the chemo-physical properties of silk fibroin films and on their interaction with neural cells

In this study, we investigated the influence of processing methods on the chemo-physical properties of silk fibroin (SF) film and on their interaction with neural cells.

The influence of the hydrophilic-lipophilic environment on the structure of silk fibroin protein

The present study examines the influence of the hydrophilic-lipophilic environment, mediated by small molecules, on the structural changes in silk protein fibroin. Small molecules mediate the various hydrophilic-lipophilic balances (HLBs) that impact the organisation of silk protein chains. Changes in the silk fibroin structure due to additives are related to the HLB value. At HLB > 10, silk fibroin primarily forms Silk I crystalline structures. Small molecules with HLB < 8.9 primarily induce the formation of Silk II crystalline structures. When 8.9 < HLB < 10, the crystalline structure of silk is related to the content of small molecules. The Silk I structure is primarily formed when the content of small molecules is low, whereas the Silk II structure is formed when the small molecule content is high. The structure of silk fibroin is maintained by regulating the HLB in the fibroin environment. This type of control for the functional design of materials may play a role in fine-tuning the biomaterial properties of silk fibroin protein.