SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Pencil

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Pencil traces drawn on print papers are shown to function as strain gauges and chemiresistors. Regular graphite/clay pencils can leave traces composed of percolated networks of fine graphite powders, which exhibit reversible resistance changes upon compressive or tensile deflections. Flexible toy pencils can leave traces that are essentially thin films of graphite/polymer composites, which show reversible changes in resistance upon exposure to volatile organic compounds due to absorption/desorption induced swelling/recovery of the polymer binders. Pencil-on-paper devices are low-cost, extremely simple and rapid to fabricate. They are light, flexible, portable, disposable, and do not generate potentially negative environmental impact during processing and device fabrication. One can envision many other types of pencil drawn paper electronic devices that can take on a great variety of form factors. Hand drawn devices could be useful in resource-limited or emergency situations. They could also lead to new applications integrating art and electronics.

Concepts: Grey Knotts, Writing, Stationery, Volatile organic compound, Pencil, Electronic engineering, Electronics, Graphite

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In 7 free recall experiments, the benefit of creating drawings of to-be-remembered information relative to writing, was examined as a mnemonic strategy. In Experiments 1 and 2, participants were presented with a list of words and asked to either draw or write out each. Drawn words were better recalled than written. Experiments 3-5 showed that the memory boost provided by drawing could not be explained by elaborative encoding (deep level of processing (LoP)), visual imagery, or picture superiority, respectively. In Experiment 6, we explored potential limitations of the drawing effect, by reducing encoding time, and increasing list length. Drawing, relative to writing, still benefited memory despite these constraints. In Experiment 7, the drawing effect was significant even when encoding trial types were compared in pure-lists between-participants, inconsistent with a distinctiveness account. Together these experiments indicate that drawing enhances memory relative to writing, across settings, instructions, and alternate encoding strategies, both within- and between-participants, and that a deep LoP, visual imagery, or picture superiority, alone or collectively, are not sufficient to explain the observed effect. We propose that drawing improves memory by encouraging a seamless integration of semantic, visual, and motor aspects of a memory trace.

Concepts: Technical drawing, Pencil, Pen, Hypothesis, Drawing, Writing, Memory, Theory

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A detailed study of hitherto unknown electrical and thermoelectric properties of graphite pencil traces on paper was carried out by measuring the Hall and Seebeck effects. We show that the combination of pencil-drawn graphite and brush-painted PEDOT:PSS films on regular office paper results in extremely simple, low-cost and environmentally friendly thermoelectric power generators with promising output characteristics at low-temperature gradients. The working characteristics can be improved even further by incorporating n-type InSe flakes. The combination of pencil drawn n-InSe:graphite nanocomposites and brush-painted PEDOT:PSS increases the power output by one order of magnitude.

Concepts: Film, Transmitter power output, Art, Electrical generator, Bismuth telluride, Pencil, Electricity, Thermoelectric effect

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Custom-made pencils containing reagents dispersed in a solid matrix were developed to enable rapid and solvent-free deposition of reagents onto membrane-based fluidic devices. The technique is as simple as drawing with the reagent pencils on a device. When aqueous samples are added to the device, the reagents dissolve from the pencil matrix and become available to react with analytes in the sample. Colorimetric glucose assays conducted on devices prepared using reagent pencils had comparable accuracy and precision to assays conducted on conventional devices prepared with reagents deposited from solution. Most importantly, sensitive reagents, such as enzymes, are stable in the pencils under ambient conditions, and no significant decrease in the activity of the enzyme horseradish peroxidase stored in a pencil was observed after 63 days. Reagent pencils offer a new option for preparing and customizing diagnostic tests at the point of care without the need for specialized equipment.

Concepts: Glucose, Pencil, Significant figures, Drawing, Horseradish peroxidase, Enzyme, Microfluidics, Accuracy and precision

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The development of portable sensors that can be used outside the lab is an active area of research in the electroanalytical field. A major focus of such research is the development of low-cost electrodes for use in these sensors. Current electrodes, such as glassy-carbon electrodes (GCEs), are costly and require time-consuming preparation. Alternatives have been proposed, including mechanical pencil-lead electrodes (MPEs). However, MPEs themselves possess numerous drawbacks, particularly structural fragility. In this paper, we present a novel pencil-graphite electrode (PGE) fabricated from a regular HB#2 pencil. This PGE is a simple, disposable, extremely low-cost alternative to GCEs ($0.30 per PGE, vs. $190 + per GCE), and possesses the structural stability that MPEs lack. PGEs were characterized by square-wave voltammetry of ferricyanide, gallic acid, uric acid, dopamine, and several foodstuffs. In all cases, PGEs demonstrated sensitivities comparable or superior to those of the GCE and MPE (LOD = 5.62 × 10-4 M PGE, 4.80 × 10-4 M GCE, 2.93 × 10-4 M MPE). Signal areas and peak heights were typically four to ten times larger for the PGE relative to the GCE.

Concepts: Uric acid, Electrochemistry, Pencil, Antioxidant, Graphite

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Thin films that integrate antireflective and antibacterial dual functions are not only scientifically interesting but also highly desired in many practical applications. Unfortunately, very few studies have been devoted to the preparation of thin films with both antireflective and antibacterial properties. In this study, mesoporous silica (MSiO2) thin films with uniformly dispersed Ag nanoparticles (Ag NPs) were prepared through a one-pot process, which simultaneously shows high transmittance, excellent antibacterial activity, and mechanical robustness. The optimal thin-film-coated glass substrate demonstrates a maximum transmittance of 98.8% and an average transmittance of 97.1%, respectively, in the spectral range of 400-800 nm. The growth and multiplication of typical bacteria, Escherichia coli ( E. coli), were effectively inhibited on the coated glass. Pencil hardness test, tape adhesion test, and sponge washing test showed favorable mechanical robustness with 5H pencil hardness, 5A grade adhesion, and functional durability of the coating, which promises great potential for applications in various touch screens, windows for hygiene environments, and optical apparatuses for medical uses such as endoscope, and so on.

Concepts: Coating, Escherichia, Gut flora, Enterobacteriaceae, Pencil, Proteobacteria, Bacteria, Escherichia coli

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Two new kinds of writing tools are popular in China’s market. One is a self-fading pen, and another is an erasable pen. The ink of the two kinds of writing tools has a remarkable characteristic that it can gradually fade or disappear under heat or be rubbed off. How to reveal the disappeared written lines is a very important question for document examiners. In this article, three series of ink line samples were made with five types of self-fading pens, 18 types of erasable pens, and three types of papers. Temperature, humidity, and lighting are known as influential factors of the process, and the effect of fading was examined. Luminescence, ultraviolet (UV), sidelight, electrostatic indentation development,low temperature, and solution revealing methods are found to be effective methods used to reveal the disappeared written lines. The best operating conditions for each method were obtained from the conducted experiments.

Concepts: Paper, Fountain pen, Pens, Ink, Pencil, Writing, Quill, Pen

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This study describes the use of electrochemical paper-based analytical devices (ePADs) drawn with graphite pencil for the determination of ascorbic acid (AA) in commercial tablets. ePADs were fabricated using vegetal paper and graphite pencil. First, the three-electrode electrochemical cell drawn using a graphical software and toner lines were laser printed on the vegetal paper surface to delimit the electrode areas. Then, the electrode regions were manually painted with graphite pencil. Afterwards, the pseudo-reference electrode was defined with the deposition of silver ink over the graphite surface. Cyclic voltammetry and square wave voltammetry (SWV) experiments were performed to optimize the electroanalytical parameters as well as to quantitatively determine the AA concentration in two commercial tables. ePADs exhibited linear behavior for a concentration range between 0.5 and 3.0 mmol L-1. The achieved limit of detection and sensitivity were 70 μmol L-1 and 0.47 μA/mmol L-1, respectively. The AA concentration levels found by SWV experiments in both CenevitTM and Energil CTM were 2.80 ± 0.02 and 3.10 ± 0.01 mmol L-1, respectively. The accuracy of the proposed devices was investigated through recovery experiments in three concentration levels and it presented values between 95 and 115%.

Concepts: Voltammetry, Acid, Ascorbic acid, Squarewave voltammetry, Pencil, Electrode, Electrochemical cell, Electrochemistry

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Paper-based microfluidic biosensors have recently attracted increasing attentions in point-of-care testing (POCT) territories benefiting from their affordable, accessible and eco-friendly features, where technologies for fabricating such biosensors are preferred to be equipment free, easy-to-operate and capable of rapid prototyping. In this work, we developed a pen-on-paper (PoP) strategy based on two custom-made pens, i.e., a wax pen and a conductive-ink pen, to fully write paper-based microfluidic biosensors through directly writing both microfluidic channels and electrodes. Particularly, the proposed wax pen is competent to realize one-step fabrication of wax channels on paper, as the melted wax penetrates into paper during writing process without any post-treatments. The practical applications of the fabricated paper-based microfluidic biosensors are demonstrated by both colorimetric detection of Salmonella typhimurium DNA with detection limit of 1nM and electrochemical measurement of glucose with detection limit of 1mM. The developed PoP strategy for making microfluidic biosensors on paper characterized by true simplicity, prominent portability and excellent capability for rapid prototyping shows promising prospect in POCT applications.

Concepts: Creative writing, Pencil, Salmonella enterica, Measurement, Writing process, Biosensor, Pen, Writing

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A simple, reliable and low-cost fabrication method is here proposed for assembling paper-based electrochemical devices using a commercial desktop digitally controlled plotter/cutter, together with ordinary writing tools. Permanent markers (tips of 1 mm) were used to create effective hydrophobic barriers on paper, while micro-mechanical pencils (mounting 4 B graphite leads, 0.5 mm in diameter) were adopted to automatically drawn precise reference, counter and working carbon electrodes. Fabrication parameters, such as writing pressure and speed, were first optimized and the electrochemical performance of these devices was then evaluated by using potassium hexacyanoferrate (II) as redox probe. The good inter-device reproducibility (4.8%) displayed by the relevant voltammetric responses confirmed that this strategy can be profitably adopted to easily assemble paper-based electrochemical devices in a highly flexible manner. The simplicity of the instrumentation used, the low cost of each single device (about 0.04 $) together with the speed of fabrication (about 2 min) are other important features of the proposed strategy. Finally, to confirm the effectiveness of this prototyping method for the analysis of real samples and rapid controls, PEDs assembled by this simple approach were successfully exploited for the analysis of vitamin B6 in food supplements.

Concepts: Scientific method, Graphite, Vitamin B6, Carbon, Assembly language, Electrochemistry, Vitamin, Pencil