Carbon Nanomaterials-Based Screen-Printed Electrodes for Sensing Applications.

Electrochemical sensors consisting of screen-printed electrodes (SPEs) are recurrent devices in the recent literature for applications in different fields of interest and contribute to the expanding electroanalytical chemistry field. This is due to inherent characteristics that can be better (or only) achieved with the use of SPEs, including miniaturization, cost reduction, lower sample consumption, compatibility with portable equipment, and disposability. SPEs are also quite versatile; they can be manufactured using different formulations of conductive inks and substrates, and are of varied designs. Naturally, the analytical performance of SPEs is directly affected by the quality of the material used for printing and modifying the electrodes. In this sense, the most varied carbon nanomaterials have been explored for the preparation and modification of SPEs, providing devices with an enhanced electrochemical response and greater sensitivity, in addition to functionalized surfaces that can immobilize biological agents for the manufacture of biosensors. Considering the relevance and timeliness of the topic, this review aimed to provide an overview of the current scenario of the use of carbonaceous nanomaterials in the context of making electrochemical SPE sensors, from which different approaches will be presented, exploring materials traditionally investigated in electrochemistry, such as graphene, carbon nanotubes, carbon black, and those more recently investigated for this (carbon quantum dots, graphitic carbon nitride, and biochar). Perspectives on the use and expansion of these devices are also considered.

Automatic Analysis of Isothermal Amplification via Impedance Time-Constant-Domain Spectroscopy: A SARS-CoV-2 Case Study

The development of sensitive and affordable testing devices for infectious diseases is essential to preserve public health, especially in pandemic scenarios. In this work, we have developed an attractive analytical method to monitor products of genetic amplification, particularly the loop-mediated isothermal amplification reaction (RT-LAMP). The method is based on electrochemical impedance measurements and the distribution of relaxation times model, to provide the so-called time-constant-domain spectroscopy (TCDS). The proposed method is tested for the SARS-CoV-2 genome, since it has been of worldwide interest due to the COVID-19 pandemic. Particularly, once the method is calibrated, its performance is demonstrated using real wastewater samples. Moreover, we propose a simple classification algorithm based on TCDS data to discriminate among positive and negative samples. Results show how a TCDS-based method provides an alternative mechanism for label-free and automated assays, exhibiting robustness and specificity for genetic detection.

Flexible Printed Circuitry on Fabric for Wearable Electronics Applications

Health awareness has increased worldwide since the COVID 2019 pandemic, creating a strong demand for wearable electronics. Wearable sensors for monitoring a patient's health are prevalent to reduce medical costs and decrease in-person clinic visits. Integrating electronics into clothes is challenging because most fabrics are porous and incompatible with the existing manufacturing methods, such as screen printing. The indirect printing method was employed to fabricate electrical circuitry on a textile substrate by printing it on a heat transfer polymer (HTP) and attaching it to the target cloths by stitching or glueing. Such a fabrication process has the potential to lead the way in developing new intelligent clothes. However, the durability of the printed circuitry in this manufacturing process on a cloth is still unknown and requires investigation. Therefore, this paper's objective is to study the durability of printed circuitries on fabric by applying constant cyclic loading. The test vehicle is a printed conductive silver interdigitating circuitry on fabric. Another test vehicle on a polyethylene terephthalate (PET) substrate was fabricated for a benchmark. A constant cyclic loading at 1Hz at a 50% duty cycle was applied to the test vehicles 100,000 times. The printed circuitry was monitored by logging the voltage in an electrical voltage divider configuration while the sensor was pressed and released. The result indicates that the fabric test vehicle can still function after the 100,000 cycles of the cyclic loading test and is comparable to that on the PET substrate. The recorded voltage-to-force values of the printed sensor on the fabric drifted upward and downward up to 3% over the loading cycles. The optical microscope observation on the cyclic loading samples showed signs of shear stresses on the printed silver and electrically conductive films, which could cause the tips of the silver interdigitating fingers to shatter. The study indicates that the properly manufactured circuits on fabric can be reliable and utilized for wearable applications. © 2022 IEEE.

Screen-printing of chitosan and cationised cellulose nanofibril coatings for integration into functional face masks with potential antiviral activity.

Masks proved to be necessary protective measure during the COVID-19 pandemic, but they provided a physical barrier rather than inactivating viruses, increasing the risk of cross-infection. In this study, high-molecular weight chitosan and cationised cellulose nanofibrils were screen-printed individually or as a mixture onto the inner surface of the first polypropylene (PP) layer. First, biopolymers were evaluated by various physicochemical methods for their suitability for screen-printing and antiviral activity. Second, the effect of the coatings was evaluated by analysing the morphology, surface chemistry, charge of the modified PP layer, air permeability, water-vapour retention, add-on, contact angle, antiviral activity against the model virus phi6 and cytotoxicity. Finally, the functional PP layers were integrated into face masks, and resulting masks were tested for wettability, air permeability, and viral filtration efficiency (VFE). Air permeability was reduced for modified PP layers (43 % reduction for kat-CNF) and face masks (52 % reduction of kat-CNF layer). The antiviral potential of the modified PP layers against phi6 showed inhibition of 0.08 to 0.97 log (pH 7.5) and cytotoxicity assay showed cell viability above 70 %. VFE of the masks remained the same (~99.9 %), even after applying the biopolymers, confirming that these masks provided high level of protection against viruses.

Characterization and application of porous PHBV-based bacterial polymers to realize novel bio-based electroanalytical (bio)sensors

The establishment of novel disruptive technologies represents a common requirement for the sustainable development as reported in the 2030 agenda established by United Nations. As demonstrated by the Covid-19 pandemic, and furtherly highlighted by the current global challenges, i.e. precision agriculture, decentralized testing, personalized medicine, the field of portable devices is growing day-by-day. Relatively to the electrochemical portable strips, globally represented by glucose strips for diabetes patients, the use of plastic-based products is still very high. In this work, two bacterial polymers have been deeply characterized and compared with the gold standard polyester that is the most used material to produce printed electrochemical strips. In particular, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV with micro-fibrillated cellulose (MFC), namely PHBV/MFC, have been produced with different porosities and have been morphologically, mechanically and electrochemically characterized. Scanning electron microscopy, contact angle, tensil tests, cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, stripping voltammetry and chronoamperometry have been used to evaluate and confirm the suitability of PHBV-based substrates for future sustainable application in the (bio)electroanalytical field. In particular these novel substrates have been applied towards the development of two sensing platforms, namely iron ions and organophosphate pesticides. As shown, in comparison with the gold standard polyester for sensors and biosensors development, the use of PHBV-based substrates allowed to reach similar detection limit and repeatability. In particular, iron ions were detected down to 140 and 150 ppb and dichlorvos was detect with an inhibition biosensor down to 0.4 and 0.5 ppb, respectively for PHBV and PHBV/MFC. These novel substrates may represent a starting point towards the development of sustainable platforms for decentralized applications. • PHBV-based materials are 100% bio-compatible and bio-degradable. • Cellulose merging is able to provide new functionalities. • Polyester-based substrates can be replaced by more sustainable ones. • A novel starting point to make sustainable electrochemical (bio)sensors. • Facile detection of iron ions and organophosphate as the case of study. [ FROM AUTHOR]

Characterization and application of porous PHBV-based bacterial polymers to realize novel bio-based electroanalytical (bio)sensors

The establishment of novel disruptive technologies represents a common requirement for the sustainable development as reported in the 2030 agenda established by United Nations. As demonstrated by the Covid-19 pandemic, and furtherly highlighted by the current global challenges, i.e. precision agriculture, decentralized testing, personalized medicine, the field of portable devices is growing day-by-day. Relatively to the electrochemical portable strips, globally represented by glucose strips for diabetes patients, the use of plastic-based products is still very high. In this work, two bacterial polymers have been deeply characterized and compared with the gold standard polyester that is the most used material to produce printed electrochemical strips. In particular, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV with micro-fibrillated cellulose (MFC), namely PHBV/MFC, have been produced with different porosities and have been morphologically, mechanically and electrochemically characterized. Scanning electron microscopy, contact angle, tensil tests, cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, stripping voltammetry and chronoamperometry have been used to evaluate and confirm the suitability of PHBV-based substrates for future sustainable application in the (bio)electroanalytical field. In particular these novel substrates have been applied towards the development of two sensing platforms, namely iron ions and organophosphate pesticides. As shown, in comparison with the gold standard polyester for sensors and biosensors development, the use of PHBV-based substrates allowed to reach similar detection limit and repeatability. In particular, iron ions were detected down to 140 and 150 ppb and dichlorvos was detect with an inhibition biosensor down to 0.4 and 0.5 ppb, respectively for PHBV and PHBV/MFC. These novel substrates may represent a starting point towards the development of sustainable platforms for decentralized applications.

Inkjet Printing: A Viable Technology for Biosensor Fabrication

Printing technology promises a viable solution for the low-cost, rapid, flexible, and mass fabrication of biosensors. Among the vast number of printing techniques, screen printing and inkjet printing have been widely adopted for the fabrication of biosensors. Screen printing provides ease of operation and rapid processing;however, it is bound by the effects of viscous inks, high material waste, and the requirement for masks, to name a few. Inkjet printing, on the other hand, is well suited for mass fabrication that takes advantage of computer-aided design software for pattern modifications. Furthermore, being drop-on-demand, it prevents precious material waste and offers high-resolution patterning. To exploit the features of inkjet printing technology, scientists have been keen to use it for the development of biosensors since 1988. A vast number of fully and partially inkjet-printed biosensors have been developed ever since. This study presents a short introduction on the printing technology used for biosensor fabrication in general, and a brief review of the recent reports related to virus, enzymatic, and non-enzymatic biosensor fabrication, via inkjet printing technology in particular.

Monitoring Symptoms of Infectious Diseases: Perspectives for Printed Wearable Sensors.

Infectious diseases possess a serious threat to the world's population, economies, and healthcare systems. In this review, we cover the infectious diseases that are most likely to cause a pandemic according to the WHO (World Health Organization). The list includes COVID-19, Crimean-Congo Hemorrhagic Fever (CCHF), Ebola Virus Disease (EBOV), Marburg Virus Disease (MARV), Lassa Hemorrhagic Fever (LHF), Middle East Respiratory Syndrome (MERS), Severe Acute Respiratory Syndrome (SARS), Nipah Virus diseases (NiV), and Rift Valley fever (RVF). This review also investigates research trends in infectious diseases by analyzing published research history on each disease from 2000-2020 in PubMed. A comprehensive review of sensor printing methods including flexographic printing, gravure printing, inkjet printing, and screen printing is conducted to provide guidelines for the best method depending on the printing scale, resolution, design modification ability, and other requirements. Printed sensors for respiratory rate, heart rate, oxygen saturation, body temperature, and blood pressure are reviewed for the possibility of being used for disease symptom monitoring. Printed wearable sensors are of great potential for continuous monitoring of vital signs in patients and the quarantined as tools for epidemiological screening.