Search

TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl)-oxidized cellulose nanofibrils (T-CNF) and silver nanowires (Ag NWs) were formulated as active inks. Their rheological properties were investigated to design optimal conditions for processing by the screen-printing process, with the aim of preparing antibacterial patterns. Rheological experiments mimicking the screen-printing process were applied to different ink formulations to investigate their thixotropic and viscosity properties. The experiments conducted at 1wt% total mass content and different ratios of T-CNF/Ag NWs showed that the recovery (%), the recovery time and the viscosity are formulation dependent. A ratio 2:1 (T-CNF/Ag NWs) and total mass content of 2.5wt% were then selected to prepare an ink suitable for screen printing. Printing defects were corrected by addition of water-soluble polymer hydroxypropyl methylcellulose (HPMC). The selected formulation printed on flexible polyethylene terephthalate (PET) substrate displayed a 67.4% antibacterial activity against E. coli in a standard contact active test, with a transparency superior to 70%, proving the promising features of the developed solution for active packaging applications. [ABSTRACT FROM AUTHOR]

There is growing interest in the application of 3D printing for demanding environments subject to gamma radiation in areas such as the nuclear industry and space exploration. In this work, the effect of gamma radiation on fused deposition modelled 3D printed parts composed of polyethylene terephthalate glycol (PETG) and acrylic styrene acrylonitrile (ASA) polymers was studied. Dose levels of up to 2.25 MGy were applied to the printed components, doses equivalent to over 1 year operating near spent nuclear fuel cells. Infrared spectroscopy showed the evidence of cross-linking by the formation of peaks corresponding to –OH and C–H bonds. Tensile and hardness testing was used to assess changes in mechanical properties and showed a reduction in ultimate tensile stress and maximum strain in parts made from both polymers, but with PETG retaining greater strength and ductility than ASA, especially at intermediate gamma exposure. Young's modulus and hardness showed either modest increases or a fairly flat response with exposure. Mechanical properties were heavily dependent on the build structure, with horizontal build samples pulled parallel to the filament direction being several times stronger than vertical build samples pulled normal to the layers. Non-irradiated samples pulled parallel to the filament direction were indicative of ductile failure, with rough surfaces, distinct infill and wall regions and evidence of thinning occurring after fracture, but irradiated fracture surfaces were flatter, smoother and without local thinning, suggesting gamma radiation-induced embrittlement in the material. For samples pulled perpendicular to the filament direction, all fractures occurred between layers, creating flat fracture surfaces with no evidence of necking and indicative of brittle failure regardless of whether the samples were irradiated. [ABSTRACT FROM AUTHOR]

Functional model inks were formulated and printed using flexography in order to assess the influence of ink extensional elasticity and print velocity on the morphological and electrical properties of printed layers. Increased extensional elasticity and higher print velocity resulted in the printing of more isotropic prints, both morphologically and electronically. Furthermore, a correlation between the prints' morphological and electrical anisotropy strongly suggests that print uniformity has a considerable influence on functionality and that ink rheology may be used to control such characteristics. Image 1 • Ink rheology was used to control flexographic print properties. • Extensional elasticity of PEDOT:PSS inks was manipulated with polyacrylamide. • Increasing ink extensional elasticity and print velocity enhanced print isotropy. • Strong correlation was found between morphological and electrical print anisotropy. [ABSTRACT FROM AUTHOR]

Photonic curing was explored as a rapid method for producing glassy carbon coatings, reducing processing time from ~ 20 h for conventional thermal processing down to ~ 1 min. A resole-type thermoset polymer resin coated on steel foil was used as a precursor, placed in a nitrogen purged container and exposed to high energy light (~ 27 J/cm2 per pulse for up to 20 pulses). Comparison samples were produced at 800 °C using a conventional nitrogen purged thermal route. For both photonic and conventionally produced coatings, Raman spectroscopy and primary peak XPS data showed sp2 bonded carbon, indicative of bulk glassy carbon. This transformation evolved with increasing number of pulses, and therefore amount of energy transferred to the coating. The produced coatings were resilient, highly smooth, with no evidence of surface defects. XPS analysis indicated greater sp3 content at the immediate surface (5–10 nm) for photonic cured carbon compared with thermally cured carbon, likely due to the local environment (temperature, atmosphere) around the surface during conversion. The ability to rapidly manufacture glassy carbon coatings provides new opportunities to expand the window of applications of glassy carbons in coatings towards large-scale high volume applications. [ABSTRACT FROM AUTHOR]

• Cellulose nanofibrils/silver nanowires ink was bar-coated on PET and PLA substrate • Defect-free and transparent films with controlled thickness were produced • The coatings displayed strong antibacterial activity and enhanced barrier properties • Up-scaling potential was proven with roll-to-roll reverse gravure coating An active ink composed of cellulose nanofibrils and silver nanowires was deposited on flexible and transparent polymer films using the bar coating process, achieving controlled thicknesses ranging from 200 nm up to 2 μm. For 350 nm thick coating on polyethylene terephthalate films, high transparency (75.6% transmittance) and strong reduction of bacterial growth equal to 89.3% and 100% was noted respectively against Gram-negative Escherichia Coli and Gram-positive Staphylococcus Aureus bacteria using AATCC contact active standard test. Retained antibacterial activity was found with films produced by reverse gravure roll-to-roll process, showing the promising capability of this antibacterial solution to be deployed industrially. Finally, the same ink was also deposited on polylactic acid substrate to investigate barrier properties: for 350 nm thick coating, a reduction of 49% of oxygen transmission rate (dry conditions) and 47% reduction of water vapor transmission rate was noted, proving the enhanced barrier properties of the coatings. [ABSTRACT FROM AUTHOR]

Background: Cataract is a major cause of visual impairment in people with diabetes, yet a paucity of data is available in low- and middle-income countries (LMICs) on this comorbidity. Thus we assessed the association between diabetes and cataract in 6 LMICs.Methods: Cross-sectional, community-based data from the Study on Global Ageing and Adult Health (SAGE) was analyzed (n = 42,469 aged ≥18 years). Five years information on self-reported diagnosis of cataract was collected. Three definitions for cataract were used: (a) Self-reported diagnosis and/or past 12-month symptoms; (b) Solely self-reported diagnosis; and (c) Surgical treatment for cataract in the past five years. Diabetes was based on self-reported diagnosis. Multivariable logistic regression was conducted to assess the associations.Results: Overall, the prevalence of diabetes was 3.1% (95%CI = 2.7-3.5%) and that of cataract based on the three different definitions was: (a) 13.3% (95%CI = 12.4-14.3%); (b) 4.4% (95%CI = 3.9-4.8%), (c) 1.7% (95%CI = 1.5-2.0%). After adjustment the association was significantly elevated: (a) OR = 2.10 (95%CI = 1.59-2.76); (b) OR = 2.62 (95%CI = 2.00-3.42); (c) OR = 2.80 (95%CI = 1.78-4.40). These associations were particularly pronounced among those aged <50 years.Conclusions: A strong association between diabetes and cataract was observed in LMICs. Considering the impact on health and quality of life and the limited treatment options especially for cataract it is mandatory to promote the prevention through bi-directional screening and treatment. [ABSTRACT FROM AUTHOR]

Purpose: To compare the foveal avascular zone (FAZ) area measurements produced by different optical coherence tomography angiography (OCTA). Methods: Healthy enrolled volunteers underwent OCTA using 2 different devices: Spectralis HRA+OCTA (Heidelberg Engineering, Heidelberg, Germany) and RS-3000 Advance (Nidek, Gamagori, Japan). Two graders measured FAZ in both superficial (SCP) and deep (DCP) retinal capillary plexuses. The SCP and DCP en face images were visualized automatically segmenting 2 separate slabs defined by the arbitrary segmentation lines created by the software of each OCT device. One grader repeated each measure twice. Results: Fifty-nine eyes were included. The mean FAZ was 0.33 ± 0.09 mm2 at the SCP and 0.57 ± 0.17 mm2 at the DCP measured with RS-3000 versus 0.30 ± 0.08 and 0.35 ± 0.08 mm2, respectively, measured with Spectralis. The measurements of the 2 devices were significantly different (p < 0.0001). The intraoperator agreement was excellent at the SCP (intraclass correlation coefficient, ICC: 0.97 with Spectralis and 0.96 with RS-3000). At the DCP, it was good with Spectralis and fair with RS-3000 (ICC: 0.85 and 0.64, respectively). The interoperator agreement was excellent for Spectralis and good for RS-3000 at the SCP (ICC: 0.97 and 0.93, respectively). It was good at the DCP with both devices (ICC: 0.74 with RS-3000 and 0.81 with Spectralis). Conclusions: FAZ measurements obtained with different OCTA devices differ. These findings should be considered in follow-up studies of patients with retinal vascular diseases. [ABSTRACT FROM AUTHOR]

In this paper we report on the development of an aerosol jet printed sensing platform integrating elements of silicon and printed electronics. To demonstrate the technology, thin film humidity sensors have been fabricated over the top surface and sides of pre-packaged integrated circuits using a combination of direct-write aerosol jet deposition and drop-casting. The resistive based sensor consists of an aerosol jet deposited interdigitated nano-particle silver electrode structure overlaid with a thin film of Nafion ® acting as a humidity sensitive layer. The fabricated sensor displayed a strong response to changes in relative humidity over the tested range (40% RH–80% RH) and showed a low level of hysteresis whilst undergoing cyclic testing. The successful fabrication of relative humidity sensors over the surface and pins of a packaged integrated circuit demonstrates a new level of integration between printed and silicon based electronics – leading to Printed-Sensor-on-Chip devices. Whilst demonstrated for humidity, the proposed concept is envisaged to work as a platform for a wide range of applications, from bio-sensing to temperature or gas monitoring. [ABSTRACT FROM AUTHOR]

Model elastic inks were formulated, rheologically characterised in shear and extension, and printed via flexography to assess the impact of ink elasticity on print uniformity. Flexography is a roll-to-roll printing process with great potential in the mass production of printed electronics for which understanding layer uniformity and the influence of rheology is of critical importance. A new set of flexo-printable Boger fluids was formulated by blending polyvinyl alcohol and high molecular weight polyacrylamide to provide inks of varying elasticity. During print trials, the phenomenon of viscous fingering was observed in all prints, with those of the Newtonian ink exhibiting a continuous striping in the printing direction. Increasing elasticity significantly influenced this continuity, disrupting it and leading to a quantifiable decrease in the overall relative size of the printed finger features. As such, ink elasticity was seen to have a profound effect on flexographic printing uniformity, showing the rheological tuning of inks may be a route to obtaining specific printed features. [ABSTRACT FROM AUTHOR]

Conductive inks based on graphite and carbon black are used in a host of applications including energy storage, energy harvesting, electrochemical sensors and printed heaters. This requires accurate control of electrical properties tailored to the application; ink formulation is a fundamental element of this. Data on how formulation relates to properties have tended to apply to only single types of conductor at any time, with data on mixed types of carbon only empirical thus far. Therefore, screen printable carbon inks with differing graphite, carbon black and vinyl polymer content were formulated and printed to establish the effect on rheology, deposition and conductivity. The study found that at a higher total carbon loading ink of 29.4% by mass, optimal conductivity (0.029 Ω cm) was achieved at a graphite to carbon black ratio of 2.6 to 1. For a lower total carbon loading (21.7 mass %), this ratio was reduced to 1.8 to 1. Formulation affected viscosity and hence ink transfer and also surface roughness due to retention of features from the screen printing mesh and the inherent roughness of the carbon components, as well as the ability of features to be reproduced consistently. [ABSTRACT FROM AUTHOR]

A novel approach is proposed to isolate meat exudate in plastic packaging trays. This exudate is responsible for limiting meat shelf life, increasing meat loss and non-recycling plastic waste. This study explores the use of specially designed capillary recesses with integrated raised rims as a means of improving liquid retention capacity in thermoformed meat trays. The presence of raised recess rims is used to enhance the valving functionality of the recesses and restrict liquid drainage during and after recess inclination. This resulted in a considerable increase in liquid retention capabilities. For pork exudate, the retention capacity of recess samples (recess diameter: 9 mm) significantly increased (p < 0.05) from 0.79 g for recesses with no rims to 2.12 g for rim-integrated recesses. The corresponding retention capacity of a recess array after introducing these rims was 2921 ± 63 mL/m2. These recesses have comparable liquid scavenging performance to absorbent meat pads (3000 mL/m2) yet are integrated within the tray material. This proves the practicality of using rim-integrated recesses in plastic meat packaging to retain exudate away and ensure fully recyclable plastic packaging. The manufacturing of these recesses is integrated into the thermoforming process for the tray body. • Rim-integrated recesses is a new technology for exudate management in PET packaging for food applications. • Developed rims considerably improve liquid pinning and restrict liquid drainage, improving retention capacity of recesses. • PET packaging film with rim-integrated recesses allow to avoid use of absorbing materials for confining exudate in packaging. • Fully recyclable PET packaging film can be achieved with rim-integrated recesses. [ABSTRACT FROM AUTHOR]

• Use of intense pulsed light on hydrothermally-grown ZnO nanowires. • Photonic annealed ZnO nanowires exhibited significant improvement in its crystallinity and conductivity. • Such annealing technique is suitable for use on substrates with low glass transition temperature. Hydrothermal growth of ZnO nanowires has been of great interest as it allows the use of organic substrates for flexible electronics applications. However, there are drawbacks on the growth technique as it is known to introduce defects in the nanowires. In this work, the use of intense pulsed light on hydrothermally grown ZnO nanowires on polyimide substrate was performed to enhance the physical and electronic properties of the nanomaterials. Such photonic annealing technique offers a rapid and effective improvement in material properties and importantly it is suitable for use on a wide variety of organic substrates, which are vital for flexible electronics. [ABSTRACT FROM AUTHOR]