Roadmap on printable electronic materials for next-generation sensors

The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g., via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g., printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world

Environmentally friendly conductive screen‐printable inks based on N‐Doped graphene and polyvinylpyrrolidone

[Excerpt] The development of polymer-based conductive inks has gained increasing interest in the areas of printed and molded electronics. Graphene-based materials are explored in this scope, reduced graphene oxide (rGO) being among the most used conductive filler components of the inks. Herein, rGO is doped with nitrogen to obtain N-rGO; the replacement of oxygen atoms by nitrogen ones increases the electrical conductivity of graphene. Polymer-based conductive inks reinforced with graphene are developed based on polyvinylpyrrolidone (PVP) as polymer binder and dihydrolevoglucosenone (Cyrene) as solvent, leading thus to environmentally friendly conductive inks. Screen-printable inks are optimized in terms of viscosity and adhesion properties, leading to printed films with sheet resistance close to Rs ¼ 1 kΩ sq1 , the graphene:PVP inks being also biocompatible and nontoxic.This work was supported by the Portuguese Foundation for Science and Technology (FCT): projects UID/FIS/04650/2021, UIDB/05256/2020, UIDP/05256/2020, PTDC/FIS-MAC/28157/2017, and PTDC/BTM-MAT/28237/2017, grants SFRH/BPD/110914/2015 (P.C.) and SFRH/BD/145741/2019 (M.F.), and Stimulus of Scientific Employments 2020.04028.CEECIND (C.M.C.) and 2020.04163.CEECIND (C.R.). The authors thank Basque Government Industry Department under the ELKARTEK program and European Union's Horizon 2020 Programme, ICT-02-2018, Flexible and Wearable Electronics, grant agreement no. 825339, WEARPLEX, wearable multiplexed biomedical electrodes

COHESIVE STRENGTH OF DENTIN RESISTÊNCIA COESIVA DA DENTINA

The bond strength of dentin adhesives to dentin has increased after each generation. Although dentin substratum is part of the bonding process, little importance has been given to measure dentin cohesive strength. The aim of this study was to evaluate the cohesive strength of dentin in human canines. Seventeen non carious canines were selected. All of them had been extracted for more than one year. The teeth were ground until dentin square samples with approximately 2 X 2 mm were obtained. They were embedded in acrylic resin and subjected to shear stress, in a Wolpert Machine, at a crosshead speed of 0.5 mm/min. The mean cohesive strength of dentin in shear mode was 33.95 (+-9.72) MPa. The fracture surfaces were observed under a X40 magnification. A finite element analysis was performed to observe the stress distribution as related to the shear test. The failure pattern was compatible with the shear test and also with the stress distribution in the finite element analysis<br>A resistência de união dos adesivos dentinários tem sido aumentada com o desenvolvimento de cada nova geração. Pouca importância tem sido dada à resistência coesiva da dentina. A proposta deste estudo foi avaliar a resistência coesiva da dentina. Dezessete caninos humanos hígidos, os quais tinham sido extraídos há mais de um ano, foram usados. Os dentes foram desgastados até a obtenção de corpos-de-prova em dentina, de formato quadrangular, com tamanho aproximado de 2 X 2 mm. Os dentes foram incluídos em resina acrílica e, então, submetidos ao teste de cisalhamento em uma máquina de ensaios universais Wolpert, com uma velocidade de 0,5 mm/min. A resistência coesiva média da dentina no teste de cisalhamento foi de 33,95 (+- 9,72) MPa. O tipo de fratura foi analisado com um aumento de 40X. Foi realizada uma análise com elemento finito, para observar a distribuição do estresse relacionada com o teste de cisalhamento. O padrão de fratura encontrado foi compatível com o tipo de teste executado e com a distribuição do estresse obtida a partir da análise de elemento finit

Roadmap on Printable Electronic Materials for Next-Generation Sensors

Abstract The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g., via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g., printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world.</jats:p