Search

The development of robust and sensitive point-of-care testing platforms is necessary to improve patient care and outcomes. Surface-enhanced Raman scattering (SERS)-based immunosensors are especially suited for this purpose. Here, we present a highly sensitive and selective SERS immunoassay, demonstrating for example the detection of horseradish peroxidase (HRP), in a sandwich format. The strength of our biosensor lies in merging: (i) SERS-immunotags based on gold nanostars, allowing exceptional intense SERS from attached Raman probes, covalent attachment of anti-HRP antibodies by a simple chemical method providing exceptional antigen binding activity; (ii) the ease of preparation of the capture platform from a regenerated cellulose-based hydrogel, a transparent material, ideal for microfluidics applications, with low background fluorescence and Raman signal, particularly suited for preserving high activity of the covalently bound anti-HRP antibodies. The sandwich complexes formed were characterised by atomic force microscopy, and by scanning electron microscopy coupled with electron diffraction spectroscopy; and (iii) the robustness of the simple Classical Least Squares method for SERS data analysis, resulting in superior discrimination of SERS signals from the background and much better data fitting, compared to the commonly used peak integral method. Our SERS immunoassay greatly improves the detection limits of traditional enzyme-linked immunosorbent assay approaches, and its performance is better or comparable to those of existing SERS-based immunosensors. Our approach successfully overcomes the main challenges of application at point-of-care, including increasing reproducibility, sensitivity, and specificity, associated with an environmentally friendly and robust design. Also, the proposed design withstands several cycles of regeneration, a feature absent in paper-SERS immunoassays and this opens the way for sensitive multiplexing applications on a microfluidic platform.

An increase in the demand for the next generation of "Internet‐of‐Things" (IoT) has motivated efforts to develop flexible and affordable smart electronic systems, in line with sustainable development and carbon neutrality. Cellulose holds the potential to fulfil such demands as a low‐cost green material due to its abundant and renewable nature and tunable properties. Here, a cellulose‐based ionic conductive substrate compatible with printing techniques that combines the mechanical robustness, thermal resistance and surface smoothness of cellulose nanofibrils nanopaper with the high capacitance of a regenerated cellulose hydrogel electrolyte, is reported. Fully screen‐printed electrolyte‐gated transistors and universal logic gates are demonstrated using the engineered ionic conductive nanopaper and zinc oxide nanoplates as the semiconductor layer. The devices exhibit low‐voltage operation (<3 V), and remarkable mechanical endurance under outward folding due to the combination of the robustness of the nanopaper and the compliance of the semiconductor layer provided by the ZnO nanoplates. The printed devices and the ion‐conductive nanopaper can be efficiently recycled to fabricate new devices, which is compatible with the circular economy concept. [ABSTRACT FROM AUTHOR]

Printed electronics answers to the emerging trend of using truly inexpensive and easily accessible techniques to design and fabricate low‐cost and recyclable flexible electronic components. Nevertheless, printing of inorganic semiconductor materials arises some barriers for flexible electronics, as they usually may require high annealing temperatures to enhance their electronic performances, which are not compatible with paper. Here, the formulation of a water‐based, screen‐printable ink loaded with zinc oxide nanoparticles that does not require any sintering process is reported. The ink is used to create the channel in fully printed electrolyte‐gated transistors on paper, gated by a cellulose‐based ionic conductive sticker. The high conformability of the electrolyte‐sticker mitigates the effect of the surface roughness of the channel, yielding transistors that operate under low voltage (<2.5 V) with a current modulation above 104 and μSat ≈ 22 cm2 V−1 s−1. These devices operate even under moderate outward bending conditions. The screen‐printed transistors are readily integrated in "universal" logic gates (NOR and NAND) by using ubiquitous calligraphy accessories for patterning of conductive paths and graphitic load resistances. This demonstrates the manufacturing of reliable and recyclable cellulose‐based iontronic circuits with low power consumption, paving the way to a new era of sustainable "green" electronics. [ABSTRACT FROM AUTHOR]

Laser irradiation to induce networks of graphene-based structures toward cost-effective, flexible device fabrication is a highly pursued area, with applications in various polymeric substrates. This work reports the application of this approach toward commonly available, eco-friendly, low-cost substrates, namely, chromatographic and office papers. Through an appropriate chemical treatment with sodium tetraborate as a fire-retardant agent, photothermal conversion to porous laser-induced graphene (LIG) on paper is achieved. Raman peaks are identified, with I2D/IG and ID/IG peak ratios of 0.616 ± 0.095 and 1.281 ± 0.173, showing the formation of multilayered graphenic material, exhibiting sheet resistances as low as 56.0 Ω sq-1. Coplanar, LIG-based, three-electrode systems (working, counter and reference electrodes) are produced and characterized, showing high current Faradaic oxidation and reduction peaks, translating in high electrochemical active area, doubling the geometric area. Good electron transfer kinetics performed exclusively with on-chip measurements are reached, with k0 values as high as 7.15 x 10-4 cm s-1. Proof-of-concept, amperometric, enzymatic glucose biosensors are developed, exhibiting good analytical performance in physiologically relevant glucose levels, with results pointing to the applicability of paper-based LIG toward efficient, disposable electrochemical sensor development, increasing their sustainability and accessibility, while simplifying their production and reducing their cost. [ABSTRACT FROM AUTHOR]

The world in the 21st century is confronted with multifaceted challenges against rapid climate change and continuous ecological disturbances caused by revolutionary socio‐economic developments, accelerated expansion of disposable electronic gadgets, and growing dependence on unrecyclable raw materials, among others. The ever‐increasing consumer demand for electronic devices is significantly contributing to the world's fastest‐growing waste stream, known as electronic waste (e‐waste), which is becoming an environmental threat at an alarming rate due to its toxic legacy. The ever‐shortening lifespan of smart technologies has created a "tsunami of e‐waste," as the United Nations has characterized it, with 50 million tons accumulated each year, of which only 20% undergo formal e‐recycling. Therefore, the challenge of optimizing the current resources management models with an aim of improving the manufacturing processes and lifecycles of electronic devices, as well as building a circular economy, has become significantly prominent. Paper/cellulose, which covers a wide range of essential needs in everyday scenarios (from packaging to writing utilities), constitutes promising candidates for the effective achievement of a circular economy. Particularly, cellulose is revealed as an advantageous material for electronic applications because of its abundant availability, which contributes to its cost‐effectiveness, straightforward fabrication process, and high recyclability and reproducibility. [ABSTRACT FROM AUTHOR]

Novel nature‐based engineered functional materials combined with sustainable and economically efficient processes are among the great challenges for the future of mankind. In this context, this work presents a new generation of versatile flexible and highly conformable regenerated cellulose hydrogel electrolytes with high ionic conductivity and self‐healing ability, capable of being (re)used in electrical and electrochemical devices. They can be provided in the form of stickers and easily applied as gate dielectric onto flexible indium–gallium–zinc oxide transistors, decreasing the manufacturing complexity. Flexible and low‐voltage (<2.5 V) circuits can be handwritten on‐demand on paper transistors for patterning of conductive/resistive lines. This user‐friendly and simplified manufacturing approach holds potential for fast production of low‐cost, portable, disposable/recyclable, and low‐power ion‐controlled electronics on paper, making it attractive for application in sensors and concepts such as the "Internet‐on‐Things." [ABSTRACT FROM AUTHOR]

A new strategy for the surface modification of bacterial cellulose (BC) through the combination of oxygen plasma deposition and silanization with trichloromethyl silane (TCMS) is described. The combined use of the two techniques modifies both the surface roughness and energy and therefore maximizes the obtained hydrophobic effect. These modified membranes were characterized by Scanning Electron Microscopy (SEM), water contact angle measurements, Fourier-transform infrared spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS), and its cytotoxic potential was investigated using both indirect and direct contact in vitro studies. The obtained results suggest an effective conjugation of TCMS to the surface of BC, leading to a highly hydrophobic surface, with a water contact angle of approximately 130º. It is also demonstrated that this is a stable and durable surface modification strategy, since BC remained hydrophobic even after 6 months, in dry conditions or after being submerged in distilled water for about a month. Importantly, this surface modification revealed no short-term cytotoxic effects on L929 and hDNFs cells. Altogether, these data indicate the successful development of a surface modification method that can be applied to BC, enabling the production of a biodegradable and hydrophobic platform that can be applied to different areas of research and industry. [ABSTRACT FROM AUTHOR]

A new concept for reusable eco-friendly hydrogel electrolytes based on cellulose is introduced. The reported electrolytes are designed and engineered through a simple, fast, low-cost, and eco-friendly dissolution method of microcrystalline cellulose at low temperature using an aqueous LiOH/urea solvent system. The cellulose solution is combined with carboxymethyl cellulose, followed by the regeneration and simultaneous ion incorporation. The produced free standing cellulose-based electrolyte films exhibit interesting properties for application in flexible electrochemical devices, such as biosensors or electrolyte-gated transistors (EGTs), because of their high specific capacitances (4-5 µF cm−2), transparency, and flexibility. Indium-gallium-zinc-oxide EGTs on glass with laminated cellulose-based hydrogel electrolytes (CHEs) as the gate dielectric are produced presenting a low working voltage (<2 V), showing an on-off current ratio ( Ion/off) of 106, a subthreshold swing lower than 0.2 V dec−1, and saturation mobility (μSat) reaching 26 cm2 V−1 s−1. The flexible CHE-gated transistors on paper are also demonstrated, which operate at switching frequencies up to 100 Hz. Combining the flexibility of the EGTs on paper with the reusability of the developed CHEs is a breakthrough toward biodegradable advanced functional materials allied with disposable/recyclable and low-cost electronic devices. [ABSTRACT FROM AUTHOR]

Self-powered devices are the need of the hour for future technologies and next-generation electronics that require both smartness and sustainability. Here, we have presented an ultra-thin (~ 0.18 mm) self-powered paper-based prototype as a touch-interactive electronic tag for next-generation Internet of Things (IoT) enabling smart security applications. A touch-interactive power paper (TiPP) was developed using in-situ polymerization followed by painting an electrode layer of graphite/silver onto it. Thus, a simple piece of paper was used for energy harvesting without having any physical separation from the electrode of the system. It instantaneously generated an electrical signal of 0.91 W m−2 due to a mechano-responsive charge transfer mechanism. Apart from using conventional electrode materials, graphite pencils were also utilized towards a more simple, environmentally friendly and cost-effective approach. Further, different arrays of TiPP have been designed to create a unique coding system (high/low signal) that can simultaneously enable self-powered sensing and an identification system. This is exhibited by a rapid but simple signal processing method used in several applications like R-G-B color codes, personal ID cards and product identification tags. A straightforward signal processing circuit that includes an effective simulation, is demonstrated to validate the working principle of such self-powered security identification tags. [Display omitted] • Polypyrrole functionalized paper used as active mechanical energy harvester. • Working electrode without physical separation gives a thin device structure. • Prototyped Security tags are interfaced with wireless communication system. • Working principle of electronic logics in the system detailed with simulation. • Prototypes are designed with green and low-cost materials. [ABSTRACT FROM AUTHOR]

The integration of bioinspired chiral cellulose nanocrystal (CNC) films into transistor devices with distinct sensing properties for left‐ and right‐handed circular polarized light (LCPL and RCPL, respectively) is reported. The CNC films with a left‐handed internal long‐range order are infiltrated with sodium ions to yield solid‐state electrolytes with photonic properties capable of LCPL reflection and RCPL transmission. They are employed as gate dielectrics in sputtered amorphous indium–gallium–zinc oxide (a‐IGZO) transistors. The obtained devices operate in depletion mode at low voltages (<2 V) with On–Off ratios of up to 7 orders of magnitude, subthreshold swings around 80 mV dec−1, and saturation mobilities up to 9 cm2 V−1 s−1. Combining the photonic character of the CNC films with the light sensitivity of a‐IGZO, the devices are capable of discrimination between LCPL and RCPL signals in the blue region. These type of devices can find application in photonics, emission, conversion, or sensing with CPL but also imaging or spintronics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eco-friendly e-paper derived entirely from recycled newspaper. • e-paper made conductive with polyaniline (PANi) functionalization. • Devices showcase impressive energy production capabilities on touch interactive. • e-paper explored as a flexible, wide-range pressure sensor with high sensitivity. • Tech integration allows IoT-ready sensors with wireless modules. This study focuses on developing multifunctional electronic paper (e-paper) using a low-cost recycling method to minimize the usage of critical raw materials. The e-paper is designed for various smart applications, such as mechano-responsive energy harvesters and pressure sensors. The emphasis is on adopting an eco-friendly approach by utilizing cellulose extracted from used newspapers, which would otherwise have been discarded. The formulated e-paper contains 100 % recycled cellulose fibers, unlike the more commonly used recycled paper, which contains around 70 % of recycled cellulose and 30 % of new pulp. The recycled paper (RP) was functionalized using polyaniline (PANi), resulting in a conductive e-paper, capable of generating electric current through a charge transfer mechanism at the PANi-Cellulose/electrode interface layer. The resulting devices demonstrate satisfactory energy production, with output voltage ranging from 16.8 to 20.25 V, output current ranging from 0.9 µA to 1.75 µA, and power density ranging from 0.18 to 0.35 Wm−2. The mechanical impulses generated by the device can successfully light up several LEDs in series. Additionally, the e-paper was investigated as a flexible, paper-based pressure sensor. The fabricated device exhibited excellent sensitivity, fast response time, and a wide detection range from 25 Pa to 12.25 kPa. The sensitivity of the pressure sensors achieved 4.21 kPa−1 within a low range of 0–1 kPa and approximately 0.008 kPa-1for a broader pressure range (2 – 12.25 kPa). Additionally, the durability of the pressure sensing devices has undergone rigorous testing, surpassing 2000 cyclic tests. [ABSTRACT FROM AUTHOR]

Abstract: A commercial sheet of paper based on natural cellulose fibers acting as permeable membrane with thin film metal cathode (Cu) and anode (Al) layers in each face was used to produce paper batteries that could be interconnected in series and rechargeable using water as electrolyte. Their electrical characteristics and the set of electrochemical reactions that support the experimental behavior observed are described in this paper. A series of integrated batteries able to supply a voltage of about 3V and a current ranging from 0.7μA to 25μA in cells with sizes of 1.2cm×3.0cm for a relative humidity in the range of 50–65% were produced in a single sheet of paper, and successfully applied to control the ON/OFF gate state of paper transistors. [Copyright &y& Elsevier]