Pencil Trace Research Articles

Pencil drawn interdigitated capacitive sensors on wood substrate

This research presents the fabrication and characterization of an interdigitated capacitive (IDC) sensor on a wooden substrate using pencil traces. The resistance of the pencil traces decreased from 100 kΩ to 5 kΩ as the pencil grade shifted from HB to 8B. Concurrently, capacitance measurements revealed an increase from approximately 5 pF for a 5-finger IDC made with HB pencil to around 32 pF for an 8B pencil counterpart. Increasing the number of pencil traces from 10 to 50 resulted in a significant decrease in resistance and a proportional increase in capacitance. Application of the IDC sensor demonstrated notable changes in capacitance upon proximity and touch, with a significant decrease upon removal. The interdigitated capacitance sensor exhibits good proximity effects and contact sensitivity in touch, with capacitance increasing exponentially from 0.3 pF (7 cm) to 1.2 pF (direct contact), highlighting its ability to detect objects with high precision. Additionally, environmental factors such as temperature and humidity influence capacitance values. These findings underscore the potential of pencil-drawn IDC sensors for responsive and adaptable applications in various fields.

Thermoelectric power measurements on graphite pencil lead and traces

Thermoelectric power measurements on graphite pencil lead and traces

Study of low-cost, flexible graphite-based sensor for human finger movement

Paper-based sensor devices have grown prominently in recent decades owing to their flexibility, light weight, biodegradability, and low cost. Pencil traces on the paper are the protuberant component to sense the physical parameter variation, and the geometry on the paper substrate plays a vital role in sensing applications. This study used the commercially available pencil as an electrode on a paper substrate that senses the mechanical strain on human finger movements. Two different geometries of the paper substrate were considered, and the optimized geometry was identified. Two different grades (HB and 8B) pencils were used as the drawing instrument to draw the graphite on the paper. The repeated experimental results show a better version of the proposed sensor for measuring human finger movements. The grade HB pencil provides excellent results compared to the other grade pencils.

Optimizing Output Performances in Stationery Papers–Based Hybrid Inorganic–Organic Flexible Thermoelectric Generators

Flexible and foldable paper‐based thermoelectric generators (PTEGs) have drawn industrial attention due to the wide applications in heat energy harvesting and sensing. Herein, optimization of the output performances of flexible and hybrid inorganic–organic PTEGs fabricated on stationery paper substrates from poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and graphite as p‐type and n‐type materials, respectively, is presented. By choosing simplistic processes such as polyethyleneimine (PEI)‐treated graphite pencil traces and brush‐painted PEDOT:PSS films, robust and sustainable PTEG devices are fabricated. It is first time shown that different qualities of stationery papers can have significant impact on the output performance of PTEGs, attributed to their variance in substrate roughness. Thus, output powers of ≈1.93 and ≈0.68 nW for ΔT = 70 K are obtained for TE generators prepared from emery and office paper legs (four‐pair assembled on Kapton), respectively, suggesting emery paper to have significant better performance. Transient flexibility and fatigue of each device type are also tested where emery paper–based PTEG appears to be more robust. A detail comparison of the device performances on the different types of paper substrates are exclusively presented experimentally and thereafter computationally validated by COMSOL modeling to predictably control and enhance the output performance of reported PTEGs.

Paper-based flexible supercapacitors with drawn van der Waals materials

Two-dimensional (2D) materials are widely used in various applications due to their extraordinary properties. In particular, their electrochemical stability, low electrical resistance, and huge specific surface area make them very interesting active materials for supercapacitors. Herein, flexible, biodegradable, and low-cost supercapacitors are introduced in a very simple way based on hand-drawing pencil traces or -rubbing molybdenum disulfide (MoS2), titanium trisulfide (TiS3) and franckeite traces on the paper. Results demonstrate that pencil-drawn paper has higher capacitance performance (∼6.39 F/g) among the suggested electrodes. Interestingly, the introduced MoS2/pencil, TiS3/pencil, and franckeite/pencil drawn paper electrodes reveal dramatic improvements with long cyclic life thanks to the occurrence of synergetic effects and higher available active cites within the heterostructures. Moreover, the assembled symmetric solid-state supercapacitors retain their performance even under applied bending, indicating their excellent potential for wearable/flexible applications.

(Invited) Chemiresistive Water Quality Sensors: Challenges and Progress

Chemiresistors are solid state devices that change their electronic properties (more specifically, the resistance of a conductive thin film or percolation network) as a result of chemical interactions with their environment. They are a well-established and widely commercialized technology for gas or vapor sensor applications. The active layer may consist of metal oxides, polymers, nanomaterials or composites. In most cases, chemisorption or catalytic activity involving the analyte results in surface doping of the active layer, although other mechanisms (such as conductivity changes due to swelling) have also been reported. A significant part of the sensing literature is taken up by reports of ChemFETs, in which case the conductivity of the active layer can also be modulated by an applied gate voltage. Gate voltage modulation is helpful for establishing the sensing mechanism and - on occasion - for distinguishing multiple simultaneous target analytes. In most cases, however, the actual sensor operation occurs at zero gate voltage, thus reducing the ChemFET to a chemiresistor. [1] Gas sensors can be operated at high voltages and without shielding the contacts to the film from gas exposure, two simplifications that are not afforded to sensors operating in aqueous environments.Water quality sensors are a surprisingly underserved area of sensor applications.[2] Important chemical water quality parameters include pH, dissolved gases, common ions and a range of toxic trace contaminants which may be ionic or uncharged, inorganic or organic. All these water quality parameters are usually monitored using colorimetric sensors, electrochemical sensors and large lab-based instruments. None of these lend themselves to low maintenance, reagent free, low power continuous operation for online monitoring. In particular, colorimetric sensors need a resupply of reagents and electrochemical sensors require reference electrodes. Chemiresistors have the potential to eliminate all these disadvantages, but there has been slow progress in adapting them to aqueous analytes. They are simple and economical to manufacture, and can operate reagent-free and with low or no maintenance. Unlike electrochemical sensors they do not require reference electrodes. Challenges include the need to prevent electrical shorts through the aqueous medium and the need to keep the sensing voltage low enough to avoid electrochemical reactions at the sensor.We have built a chemiresistive sensing platform for aqueous media. The active sensor element consists of a percolation network of low-dimensional materials particles that form a conducting film, e.g. from carbon nanotubes, pencil trace, exfoliated graphene or MoS2. The first members of that platform were free chlorine sensors,[3-5] but we have also demonstrated pH sensitive films [6,7] and cation sensors.[8] While there are some challenges associated with expanding the range of accessible analytes,[9] we have recently expanded the applicability of our platform, in particular anions and cations that are commonly present as pollutants in surface and drinking water. Our sensors can be incorporated into a variety of systems and will also be suitable for online monitoring in remote and resource-poor locations.

Nanocarbon Based Chemiresistive Detection of Monochloramine in Water

The use of chloramine as a disinfectant in water treatment plants is becoming popular due to its lower reactivity and higher stability than free chlorine.1–3 Chloramines are produced by the reaction of free chlorine (HOCl, OCl-) with nitrogen compounds to form monochloramine (NH2Cl), dichloramine (NHCl2) or nitrogen trichloride (NCl3), depending on pH and N/Cl ratio.4 Dichloramine and nitrogen trichloride tend to create odour and taste problems in drinking water. Thus, only monochloramine is preferred for disinfection. Typically, 0.5-2 mg/L of monochloramine is maintained in the water distribution system.5 Maintaining the concentration level of monochloramine is crucial to prevent pathogen growth in the drinking water. Currently, there is no direct method to measure chloramine. However, U.S. EPA-approved amperometric titration and colorimetric methods are available which can be used to measure total and free chlorine in aqueous media.2 An amperometric titration method (SM 4500-Cl D) is capable of distinguishing 3 common forms of chlorine: Cl2 / HOCl / OCl-, NH2Cl, and NHCl2. However, it fails at concentrations greater than 2 mg/L (as Cl2).2,3 Even though this method is not affected by common oxidizing agents, temperature changes, turbidity, and colour, it does require a greater degree of skill. Operationally simpler, N,N-diethyl-p-phenylenediamine (DPD) methods (ferrous and colorimetric) are used to measure free and total chlorine and then their subtraction gives the concentration of monochloramine, assuming no NHCl2 and NCl3 are present. DPD methods are subjected to interferences like copper, manganese (oxidized), iodide and chromate.6 Additionally, the DPD method is not suitable for continuous monitoring of monochloramine which is essential in water distribution plants to maintain the appropriate concentration of disinfectant.2,3,7 Here we demonstrate a chemiresistive sensor array for the continuous monitoring of chloramine in the water. Chemiresistive sensors are cheap, robust and use low power. These sensors detect an analyte through changes in the electronic properties of the transducing element. A nanocarbon network was airbrushed onto the frosted side of a microscope glass slide as the transducing element between two pencil trace contact patches. Copper tapes were placed on top of the pencil patches and then covered with a dielectric. 10 mV voltage was applied for the measurements, and the changes in resistance were measured as the analyte interacted with the transducing element. The surface of the nanocarbon network is functionalized with suitable dopant molecules by submerging the sensor in the molecule solution. This array of molecules will be able to capture the parameters to be able to classify the type of chloramine present in water. Fresh chloramine solution is prepared before each experiment by adding NH4Cl and NaOCl in Phosphate Buffered Saline (PBS). Sensor responses are recorded as positive current change with increasing concentrations of monochloramine. Here the hole density of the inherently p-doped substrate increases when exposed to monochloramine, and thereby resulting in increasing current. Sensors can be reset with ascorbic acid or water. Sensors were tested with 0.054 ppm to 1.437 ppm of monochloramine in pH 7.5 and 8.5. Functionalized sensor devices showed a considerably higher response than the unfunctionalized ones. The tap water sample was tested with the calibrated devices. We have therefore demonstrated a robust sensor array capable of continuously monitoring chloramine in aqueous media.

Metallic memorandum books—history, materials and conservation

Metallic memorandum books were a common stationery item in the nineteenth century—small notebooks of varying dimensions, sold with a special ‘metallic’ pencil. However, few extant examples survive in collections. Very little published information exists regarding their manufacture, distribution and use. Research sought to discover their likely prevalence in Australian collections, materials used in their manufacture, and the conservation implications of their construction. Data analysis of Australian newspapers held on the Trove website found evidence of their use between 1831 and 1915, primarily between 1850–1870, across Australia. Contemporary accounts suggest they were an everyday item used by workmen, artists and explorers, amongst others. This research technique shows potential for further art materials research. XRF analysis of a sample notebook found low or trace amounts of lead and tin within the metallic pencil and low or trace amounts of barium and strontium in the paper. FTIR analysis of the paper returned a spectrum that matched to barium sulphate. This corresponds to historical accounts and makes them materially similar to metalpoint drawings. They are therefore likely to experience similar condition issues, such as marking, staining and flaking of the prepared surface, and may not respond well to aqueous conservation treatments.

Single material thermocouples from graphite traces: Fabricating extremely simple and low cost thermal sensors

Thermocouples are a universal type of thermal sensors routinely used in different applications for the measurement and monitoring of temperature. Traditionally, they are constructed from two dissimilar conductors. In this work, single material thermocouples are fabricated using graphite pencil traces patterned on cellulose paper. The different magnitudes of the Seebeck coefficients in different grade pencils facilitate successful construction of a graphite‐only thermocouple sensor. These extremely simple, low-cost, and eco-friendly thermocouple sensors have shown stable and reliable sensitivity of 7.4 (±0.3) µVK−1, indicating a good temperature resolution of better than 0.2 K. With the advantage of simple and solvent-free fabrication process, such devices can be developed as cheap, environmentally friendly, and disposable thermal sensors.

Low-cost fabrication of a pH sensor based on writing directly over parchment-type paper with pencil

Herein, we introduce a low-cost and straightforward method for preparing pH sensors based on parchment-type paper and pencil traces as a base and electrode, respectively. The hydrophobic feature of the parchment paper supports the relatively long life of the proposed pH sensor. The results indicate that the present sensors have a Nernstian response with a Nernstian slope of 52.1 ± 1.5 mV/pH and a good linearity of 0.995 from pH 4 to 10. The stability of the proposed electrode is approximately 0.75 mV/h. The prepared electrodes show a relatively long operating life compared with the published results of ordinary paper-based pH devices. However, the Nernstian factor decreases over time and stabilizes at approximately 28 mV/pH after two months. This approach provides a low-cost and reproducible pH sensor.

Paper Thermoelectrics by a Solvent-Free Drawing Method of All Carbon-Based Materials.

As practical interest in the flexible or wearable thermoelectric generators (TEGs) has increased, the demand for the high-performance TEGs based on ecofriendly, mechanically resilient, and economically viable TEGs as alternatives to the brittle inorganic materials is growing. Organic or hybrid thermoelectric (TE) materials have been employed in flexible TEGs; however, their fabrication is normally carried out using wet processing such as spin-coating or screen printing. These techniques require materials dissolved or dispersed in solvents; thus, they limit the substrate choice. Herein, we have rationally designed solvent-free, all carbon-based TEGs dry-drawn on a regular office paper using few-layered graphene (FLG). This technique showed very good TE parameters, yielding a power factor of 97 μW m–1 K–2 at low temperatures. The p-type only device exhibited an output power of up to ∼19.48 nW. As a proof of concept, all carbon-based p-n TEGs were created on paper with the addition of HB pencil traces. The HB pencil exhibited low Seebeck coefficients (−7 μV K–1), and the traces were highly resistive compared to FLG traces, which resulted in significantly lower output power compared to the p-type only TEG. The demonstration of all carbon-based TEGs drawn on paper highlights the potential for future low-cost, flexible, and almost instantaneously created TEGs for low-power applications.

Collaborative poaching: Compossibilities, notes, traces and narrative imagination

This article suggests a method for cultivating a collaborative method of shared visual note-taking on seminar readings and discussions, built on the method of creative ‘poaching’ of each other’s contributions, using pencil and simple tracing technique on transparent papers. The method was developed and tested in a decade of workshops with the author and varying groups of participants, students, researchers and professionals, in academic text-based discussions, lectures and seminars. The method, speculative and collaborative, aims to assemble the participants’ ideas and contributions in compossible ways, that is, possibilities that support each other to build more convivial forms of annotation and idea generation, and where contributions flow into each other and with no clear delineation of order or between authors/contributors. This method of collaborative poaching produced convincing results and could be used as an exercise in semi-structured discussions and their creative documentation, cultivating a multiplicity of perspectives on human values and also support what Martha Nussbaum calls a ‘narrative imagination’.

Carbon-MEMS based rectangular channel microarrays embedded pencil trace for high rate and high-performance lithium-ion battery application

C-MEMS based rectangular channel microarrays anode for high performance Li-ion battery.

WS2 Nanosheet/Graphene Heterostructures for Paper-Based Flexible Photodetectors

We report a low-cost and green synthesis approach to produce high-performance optoelectronics based on WS2-decorated pencil trace on ordinary cellulose paper. It is noteworthy that the photodetector was prepared via simply nontoxic solution-processed WS2 nanosheets, pencil-drawn graphene conducting films, and biodegradable papers. Portable and flexible electronics based on WS2/graphene show excellent photoresponse in a broad spectral region from visible to near IR because of plasmonic improvement and efficient photoabsorption. Liquid-phase-exfoliated atomically thin WS2 nanosheets were decorated on a conducting film of pencil trace using the large area electrophoretic deposition technique. The photodetector based on the WS2/graphene heterostructure shows excellent temporal photoresponse with a responsivity of 0.439 A/W, a detectivity of 1.41 × 1010 Jones, and an external quantum efficiency of 81.39%. The high-performance photodetector shows piezoresistive modulation in electric transport. The device response was investigated up to 500 bending cycles. Finally, the present finding advocates the great development over previously reported nonbiodegradable and small-area optoelectronic devices.

Thermoelectric Paper: Graphite Pencil Traces on Paper to Fabricate a Thermoelectric Generator

AbstractPaper‐based thermoelectric generators are a promising and economical alternative to expensive organic conductors that are normally preferred for flexible generators. In the present work, graphite pencil traces on regular Xerox paper are successfully employed to constitute a thermoelectric generator. In conjunction with polyethylenimine polymer, the graphite traces act as both the p‐type and n‐type thermoelectric “legs,” of a graphite‐based thermoelectric generator. The fabrication method is facile and requires no conducting paste or silver paste to connect individual thermoelectric legs. A test module containing five pairs of p‐n legs is fabricated on paper to test its performance. The device produces a thermoelectric voltage of 9.2 mV, generating an output power of 1.75 nW at a temperature difference of ≈60 K. The present work demonstrates that ordinary pencil on paper may be used as the foundation for a cheap, flexible, easily disposable, and environmentally friendly thermoelectric generator.

Switchable Dopants on Percolation Networks of 2D Materials for Chemiresistive Sensing Applications in Aqueous Environments

Permanent doping of semiconductors and low-dimensional structures to modulate their electronic properties is a well-established concept. Even in cases where doping of thin films by analytes (e.g. carbon nanotubes by ammonia) is applied in sensors, it is only reversed by physical removal of dopant molecules, e.g. heating. We have introduced the concept of molecular switches as chemical dopants for thin nanocarbon (or other 2D-materials) films. These molecules can be switched between doping and non-doping states in the presence or absence of a particular analyte. They impart selectivity not only due to their change in doping behavior, but also by physically blocking other potential dopants in the analyte solution from interacting with the conductive film. The resulting structures can act as chemiresistive films.Chemiresistive sensors are a well-established technology for gas-phase sensing applications. They are simple and economical to manufacture, and can operate reagent-free and with low or no maintenance. Unlike electrochemical sensors they do not require reference electrodes. While in principle they can be made compatible with aqueous environments, only a few such examples have been demonstrated. Challenges include the need to prevent electrical shorts through the aqueous medium and the need to keep the sensing voltage low enough to avoid electrochemical reactions at the sensor. We have built a chemiresistive sensing platform for aqueous media. The active sensor element consists of a percolation network of low-dimensional materials particles that form a conducting film, e.g. from carbon nanotubes, pencil trace, exfoliated graphene or MoS2. The first member of that platform was a free chlorine sensor.[1-3] We are currently working to expand the applicability of our platform to other relevant species, in particular anions and cations that are commonly present as pollutants in surface and drinking water.[4] Our sensors can be incorporated into a variety of systems and will also be suitable for online monitoring in remote and resource-poor locations.[1] L. H. H. Hsu, E. Hoque, P. Kruse, and P. R. Selvaganapathy, A carbon nanotube based resettable sensor for measuring free chlorine in drinking water. Appl. Phys. Lett. 106 (2015) 063102.[2] E. Hoque, L. H. H. Hsu, A. Aryasomayajula, P. R. Selvaganapathy, and P. Kruse, Pencil-Drawn Chemiresistive Sensor for Free Chlorine in Water. IEEE Sens. Lett. 1 (2017) 4500504.[3] A. Mohtasebi, A. D. Broomfield, T. Chowdhury, P. R. Selvaganapathy, and P. Kruse, Reagent-Free Quantification of Aqueous Free Chlorine via Electrical Readout of Colorimetrically Functionalized Pencil Lines. ACS Appl. Mater. Interfaces 9 (2017) 20748-20761.[4] P. Kruse, Review on Water Quality Sensors. J. Phys. D 51 (2018) 203002. Figure 1

Digitalized pencil trace modified electrodes for real time evaluation of salicylic acid in detached Arabidopsis thaliana leaves during regeneration

Plants have excellent abilities to regenerate from detached tissues, in which various phytohormones play critical roles. It has been reported that jasmonate and auxin appeared sequentially during direct de novo root regeneration (DNRR) after leave detachment. However, the role of salicylic acid (SA) is still unknown in this procedure although it is another important plant hormone. We have demonstrated the potential of electrochemical sensors for real time screening of SA but the stability still needed to be improved. Herein a digital plotter was used to modify the carbon tape modified electrodes with pencil traces in order to improve the reproducibility. The modified electrodes in paper-based analytical devices were applied to monitor SA during direct DNRR. The drawing routines and the distances between two close traces were optimized. Our results showed that the carbon tape modified electrodes achieved more reproducible responses of SA. Combined with in vivo sampling, the results using our approach demonstrated that amounts of SA in the wild Arabidopsis thaliana leaves during direct DNRR reached highest at around 72 h after detachment and then decreased, implying that the wave of SA contents might follow that of auxin during direct DNRR. The application of the digital plotter offered a cost-effective and more reproducible method for preparation of disposable working electrodes, which might be extended for other biochemical assays.

Pencil-on-paper flexible electronics for daily sensing applications

PurposeInspired by the development of eco-friendly flexible electronics, this paper aims to present a series of paper-based electronics drawn by pencils, which can be used as favorable sensing elements in daily life.Design/methodology/approachPencil traces are deposited on the porous surface of Xerox paper by the mechanical exfoliation during writing process, which can be used as basic components to construct functional electronics for daily sensing applications. By changing pencil grade, the obtained traces can work as conductive wires, electrodes, resistors and piezoresistive gauges.FindingsThe experimental results confirm their practical applications in sensing several daily activities, including finger motion, touching and the temperature of water in paper cup. Moreover, the used electronics can be easily handled and recycled.Research limitations/implicationsThe shortage in functionality, reliability and performance consistency induced by manual operation is an evident challenge, which makes the pencil-on-paper devices more suitable to work as a temporary solution to satisfying the demands from emergency circumstances.Originality/valueThe pencil-on-paper devices, motivated by the electroconductibility and piezoresistivity of pencil trace, can be explored as sensing prototypes in detecting daily activities. Meantime, their advances in easy accessibility, rapid fabrication, low cost and eco-fitness endow them excellent capacity of meeting the “on-site, real-time” demands.

Real time sensing of salicylic acid in infected tomato leaves using carbon tape electrodes modified with handed pencil trace

Plants encounter phytopathogens frequently and phytohormones (such as salicylic acid, SA) are critical for their corresponding defensive functions. Monitoring SA in real time could help us understand its regulation mechanisms more clearly. Previously we have demonstrated that carbon tape working electrodes modified with carbon nanotubes could be utilized for quantification of SA in tomato leaf samples with the weights at the level of micrograms. Herein inexpensive pencils were used to modify the carbon tape with the pencil trace as the working electrodes by hand drawing. The pencil types and the trace layers were optimized for screening SA, implying that the carbon tape could maintain the handed pencil trace with its nanostructure. The carbon tape electrodes modified with handed pencil trace were integrated in the paper-based devices for real time monitoring SA in tomato leaves infected by Pseudomonas syringae pv. Tomato DC3000 (pst DC3000). Our results showed that the contents of SA in the surrounding area of the infection center increased significantly after inoculation of pst DC3000 within 24 h. The modification of working electrodes with handed pencil trace provided a low cost and effective method for sensitive detection of SA. The similar approach and platform might be extended for more biochemical applications.

Pencil on paper as low cost alternative resistors

Pencil leads can be used to draw resistors, which are low-cost and easy to obtain. Not all types of pencils are considered good for pencil resistors because pencil lead is made up of graphite, an allotrope of carbon. Resistance of graphite varies with the grades used during manufacturing, as such we aimed to review and test several types of pencils would be best for developing DC pencil circuits. The resistance of pencil traces was found to depend on pencil grade used in drawing, width, and thickness or numbers of layers. The 6B grade was found to be the best pencil for drawing resistors. The applied pressure and bending paper inward and outward was found to affect the resistance.