Nanopaper-based sensors

Green Preparation and Functional Properties of Reinforced All-Cellulose Membranes Made from Corn Straw

In this study, all-cellulose nanocomposite (ACNC) was successfully prepared through a green and sustainable approach by using corn stalk as raw material, water as regeneration solvent, and recyclable two-component ionic liquid/DMSO as the solvent to dissolve cellulose. The morphology and structural properties of ACNC were determined by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis, indicating homogeneity and good crystallinity. In addition, a comprehensive characterization of ACNC showed that CNF not only improved the thermal stability and mechanical characteristics of ACNC, but also significantly improved the oxygen barrier performance. The ACNC prepared in this work has a good appearance, smooth surface, and good optical transparency, which provides a potential application prospect for converting cellulose wastes such as corn straws into biodegradable packaging materials and electronic device encapsulation materials.

Paper-Based Humidity Sensors as Promising Flexible Devices: State of the Art: Part 1. General Consideration

In the first part of the review article "General considerations" we give information about conventional flexible platforms and consider the advantages and disadvantages of paper when used in humidity sensors, both as a substrate and as a humidity-sensitive material. This consideration shows that paper, especially nanopaper, is a very promising material for the development of low-cost flexible humidity sensors suitable for a wide range of applications. Various humidity-sensitive materials suitable for use in paper-based sensors are analyzed and the humidity-sensitive characteristics of paper and other humidity-sensitive materials are compared. Various configurations of humidity sensors that can be developed on the basis of paper are considered, and a description of the mechanisms of their operation is given. Next, we discuss the manufacturing features of paper-based humidity sensors. The main attention is paid to the consideration of such problems as patterning and electrode formation. It is shown that printing technologies are the most suitable for mass production of paper-based flexible humidity sensors. At the same time, these technologies are effective both in the formation of a humidity-sensitive layer and in the manufacture of electrodes.

Moving toward smart biomedical sensing

The development of novel biomedical sensors as highly promising devices/tools in early diagnosis and therapy monitoring of many diseases and disorders has recently witnessed unprecedented growth; more and faster than ever. Nonetheless, on the eve of Industry 5.0 and by learning from defects of current sensors in smart diagnostics of pandemics, there is still a long way to go to achieve the ideal biomedical sensors capable of meeting the growing needs and expectations for smart biomedical/diagnostic sensing through eHealth systems. Herein, an overview is provided to highlight the importance and necessity of an inevitable transition in the era of digital health/Healthcare 4.0 towards smart biomedical/diagnostic sensing and how to approach it via new digital technologies including Internet of Things (IoT), artificial intelligence, IoT gateways (smartphones, readers), etc. This review will bring together the different types of smartphone/reader-based biomedical sensors, which have been employing for a wide variety of optical/electrical/electrochemical biosensing applications and paving the way for future eHealth diagnostic devices by moving towards smart biomedical sensing. Here, alongside highlighting the characteristics/criteria that should be met by the developed sensors towards smart biomedical sensing, the challenging issues ahead are delineated along with a comprehensive outlook on this extremely necessary field.

Direct conversion of raw wood to TEMPO-oxidized cellulose nanofibers

A direct production route of cellulose nanofibers (TOCN-D) from raw wood particles of paulownia using simultaneous bleaching and TEMPO oxidation process was specifically investigated and introduced. For comparison, we prepared cellulose nanofibers (TOCN-C) through a common route of TEMPO oxidation of cellulose fibers, and cellulose nanofibers with disk grinding (GCNF). FE-SEM analysis showed that the average diameter of TOCN-D (5 ± 3 nm) was similar to that of TOCN-C (6 ± 3 nm). XRD results confirmed that the crystal properties of TOCN-D and that of TOCN-C were almost the same. TOCN-D and TOCN-C showed similar chemical, thermal and optical properties in FTIR, TGA and transparency tests, respectively. The nanopaper made from TOCN-D showed high Young's modulus (13.8 GPa) and tensile strength (233 MPa), which were similar to those of TOCN-C nanopaper. Owing the aforementioned similarities, it is concluded that the TOCN-D produced through direct route is a technically, environmental-friendly and economically valuable product.

Paper-Based Screen-Printed Electrodes: A New Generation of Low-Cost Electroanalytical Platforms

Screen-printed technology has helped considerably to the development of portable electrochemical sensors since it provides miniaturized but robust and user-friendly electrodes. Moreover, this technology allows to obtain very versatile transducers, not only regarding their design, but also their ease of modification. Therefore, in the last decades, the use of screen-printed electrodes (SPEs) has exponentially increased, with ceramic as the main substrate. However, with the growing interest in the use of cheap and widely available materials as the basis of analytical devices, paper or other low-cost flat materials have become common substrates for SPEs. Thus, in this revision, a comprehensive overview on paper-based SPEs used for analytical proposes is provided. A great variety of designs is reported, together with several examples to illustrate the main applications.

All-Cellulose Composites: A Review of Recent Studies on Structure, Properties and Applications

Nowadays, there is greater demand for greener materials in societies due to environmental consciousness, depleting fossil fuels and growing ecological concerns. Within the foreseeable future, industries and suppliers will be required to be more aware of challenges faced due to the availability of resources and use more sustainable and renewable raw materials. In this context, cellulose can be expected to become a vital resource for materials owing to its abundance, versatility as a biopolymer, several different forms and potential applications. Thus, all-cellulose composites (ACCs) have gained significant research interest in recent years. ACC is a class of biocomposites in which the matrix is a dissolved and regenerated cellulose, while the reinforcement is undissolved or partly dissolved cellulose. This review paper is intended to provide a brief outline of works that cover recent progress in the manufacturing and processing techniques for ACCs, various cellulose sources, solvents and antisolvents, as well as their properties.