Gel Pen Inks Research Articles

An experimental study on distinguishing gel pen ink stains using desorption electrospray ionisation mass spectroscopy combined with the K-means algorithm

Abstract In the realm of document examination, the identification of suspicious alterations to handwritten documents is an important factor in case characterisation. Investigating the differences in gel pen ink compositions has significant implications. In this study, we used desorption electrospray ionisation mass spectrometry (DESI-MS) to analyse the ink compositions of gel pens. The methodology involved the following steps. (1) Sample selection: a total of 227 gel pens available in the market were procured for the study. (2) Pre-experimental parameter exploration: preliminary experiments were performed to optimise the experimental parameters. (3) Analytical technique: DESI-MS was used to collect compositional data from the gel pen ink samples, without requiring pre-treatment of the samples. (4) Data analysis: the obtained data were analysed using the Davies–Bouldin index, Calinski–Harabasz index, and K-means algorithm for ink sample classification. The experimental findings indicated that DESI-MS is a viable method for examining the ink compositions of gel pens. Notably, the testing process is minimally destructive and does not necessitate pre-treatment of the samples. Furthermore, variations in the ink compositions were observed among different models of gel pens within the same brand, and the extent of the variation in the composition varied across brands. Additionally, there were instances in which the ink compositions of different brands of gel pens exhibited similarities.

Extraction of Dye from Waste Blue Gel Pen Ink Using the Voltine Method and Its Application in Fabric Dyeing: An Eco-friendly Approach

Extraction of Dye from Waste Blue Gel Pen Ink Using the Voltine Method and Its Application in Fabric Dyeing: An Eco-friendly Approach

Differentiation of blue gel pens using visible spectroscopy coupled with chemometric techniques

Ink analysis is one of the most important and keydimension of forensic document examination (FDE). It is performed to compare, identify, characterize and discriminate different kinds of inks present on questioned document. It becomes key evidence in forensic document examination. In the present work, thirty-eight blue gel pens are discriminated using visible spectroscopy coupled with chemometric techniques. The recorded spectra were visually compared followed by chemometric techniques of principal component analysis (PCA) and linear discriminant analysis (LDA). Discriminating power for visual comparison, PCA and LDA are 58.18%, 100% and 100% respectively. Developed PCA model is validated and 100% accuracy, precision, sensitivity and specificity are achieved. Blue gel pen inks were 100% correctly differentiated on the basis of their brands using PCA followed by LDA. The utilized approach is fast and provides reproducible results. The results of present work demonstrate that potential utility of conventional and cost-effective visible spectroscopy can be improved by coupling it with these chemometric techniques. Major advantage of present research is the minimum damage caused to document. This study establishes a method which provides proof of concept discrimination of the gel pen samples. The methodology adopted in present work can be applied in the alteration cases in examination of suspected documents.

Ink Analysis for Forensic Investigations: An Integrated Approach Incorporating Physico-chemical Techniques and Image Processing

Background: Criminal actions using falsified papers are on the rise. Any changes to the document's content are usually made with ballpoint and gel pens. All changes made to a document using a pen necessitate ink analysis. Thus, a quick and accurate ink analysis process must be created to cope with the challenges associated with counterfeiting. Aim: This study aims to analyze several brands of ballpoint and gel pen inks using physicochemical and computational techniques and provide a database of the results. Methods: A total of 24 pen samples from various brands were colour-tested first, followed by an optical test using ImageJ software. The composition of each ink sample was distinguished using the non-destructive method ATR-FTIR, followed by a destructive technique TLC. Lastly, a computational technique algorithm was applied for rapid and desirable results. Results: The results distinguished each brand based on RGB measures and mean values. The differentiation of each sample using ATR-FTIR spectroscopy was challenging due to similar structural characteristics. However, TLC (destructive) was used with several solvent systems. Ballpoint pen inks separated well in all solvent systems, with the greatest results achieved in solvent systems 2 and solvent system 4. The TLC spots were identical, but when evaluated digitally using MATLAB, substantial changes were visible, which were utilized to differentiate similar colour inks from various brands. Conclusion: The chemical approaches, in conjunction with the computational techniques, offered a rapid and sophisticated method that allowed for better distinction of the inks and provided more accuracy in substantially less time than typical methods employed in forensic laboratories.

Painting sustainable wearables: facile and economical all-recycled dual temperature-motion wearable sensor for monitoring of human temperature and joint movements

World is seeing rapid increase in smart wearable electronic devices and gadgets especially for personal healthcare and activity monitoring. It is estimated that e-waste generation will reach 75 million tons by 2030 which is posing life-threatening complication by polluting environment. To build sustainable and green world; facile, economical, multi-functional, biodegradable, and recyclable wearable sensors have great potential in human health and activity monitoring in developing countries, especially in rural areas due to budgetary constraints and geographic inaccessibility. This paper presents a facile, and economical, all-recycled dual temperature-motion (ARDTM) wearable sensor patch to monitor human body temperature and joint movements. The proposed ARDTM wearable sensor is fabricated by recycling/re-using e-waste (dry cells) to get graphite and paper. Paper is employed as the substrate due to its low-cost, abundance, flexibility, biocompatibility, biodegradability, and disposability. The graphite extracted from the discarded dry cells is mixed with gel pen ink to make conductive graphite paste. Resistive temperature sensor and capacitive motion sensor are brush painted on sticky-note paper using conductive graphite paste. The sensors are integrated together to monitor body movements and temperature simultaneously in a compact and decoupled manner. To demonstrate the isolation of both sensors, the response of the dual sensor patch is examined simultaneously for body temperature and wrist movement. The temperature sensor is characterized by measuring change in resistance over a temperature range of 25 °C – 65 °C in addition to body temperature and it demonstrated a sensitivity of ∼335 Ω/°C. For monitoring human body movements, the capacitive response of motion sensors is tested on several body parts especially the wrist, knee, elbow, and finger. The ARDTM wearable sensor is facile, low-cost, multipurpose, biodegradable, compact and can be used to simultaneously monitor human activities and health. Our approach realized multi-purpose wearable sensor by recycling/re-using paper and e-waste, which provides a way forward for the sustainable and green development of wearable sensors by mitigation of e-waste.

Rapid and simultaneous determination of nine volatile solvents in ink entries with improved gas chromatography

Volatile compounds such as alcohols and ethers are added into ballpoint pen inks, gel pen inks and water-based rollerball pen inks as humectants or solvents. The composition of solvents in inks and their amounts of evaporation are critical evidence for identifying the types of pens or dating ink entries. Relative quantification methods using gas chromatography (GC) or gas chromatography coupled to mass spectrometry (GC/MS) were employed to analyze alcohols and ethers in most previously reported studies, but they were not convenient for researchers of the same field to compare results. Besides, those methods are time-consuming, with an average time of 23−36 min per run. Therefore, in this work a rapid quantification method was established to simultaneously determine nine volatile solvents commonly existed in ink entries, including ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, diethylene glycol, triethylene glycol, benzyl alcohol, 2-phenoxyethanol (PE) and diethylene glycol monoethyl ether (DGME), while 1,3-butanediol was used as the internal standard. A GC system equipped with flame ionization detector (FID) was adopted to separate the nine target analytes. The analysis time was reduced to 9–12 min. The linearity of the calibration curves was good in the ranges of 10–3000 ng/cm for all target analytes, and Pearson correlation coefficients were all greater than 0.999. The results indicate that the established method provides sensitive, precise, and accurate quantification of nine volatile solvents in ink entries. What’s more, this method raises analytical efficiency greatly and has lower requirements of instruments, showing promising application in questioned document examination and ink dating.

Characterization and discrimination of volatile compounds in gel-pen ink via headspace-gas chromatography-ion mobility spectrometry combined with chemometric strategies

Handwriting is usually suspected of any alterations or falsifications in litigation activities. Hence, handwriting verification of documents is an important part to solve legal dispute caused by parties in the field of forensic science. For the first time, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was applied for the reliable analysis of the distinguishment of sophisticated compositions in ink samples. The volatile organic compounds of seven common ink species were investigated. Topographic photographs of HS-GC-IMS provided the differentiation of various gel-pen inks with quickly and intuitively. Based on visual assessments and precise qualitative analysis, a total of 95 selected volatile compounds were characterized on feature map. Ketones, eaters and alcohols were the significant components from the recognizable fingerprint gallery in HS-GC-IMS. Chemometric models, such as Principal component analysis (PCA), heatmap and Hierarchical cluster analysis (HCA), clearly identified the differences of volatile substances and discriminated the origins of gel-pen ink samples. Therefore, HS-GC-IMS as an effective and accurate comprehensively instrument was appropriate for the discrimination of various gel-pen ink species, which would contribute to establish the corresponding ink database and further explain the document dating in forensic science.

Application of physical techniques for establishment of homogeneous and heterogeneous intersecting strokes between laser toner and writing pen inks

In questioned document examination, establishing the sequence of crossing lines has always been a complex task for a forensic document examiner. This study aims to determine the sequence of homogeneous and heterogeneous crossing lines prepared by using laser printer and writing pen inks (ballpoint and gel pens) through optical methods. The samples were examined under stereomicroscope and LED microscope. The outcomes were based on examination of intersection under LED microscope and stereomicroscope. It was observed that stereomicroscope gave 100% accurate results in establishing the sequence of crossing lines of laser printer and writing pen inks (of same and different colours). Under LED microscope, the only feature observed was compression of laser toner stroke by ballpoint and gel pen ink lines.

VSC®-8000/HS- A Robust Tool for Differentiation of Overlapped Black Pen Inks in Fraudulent Documents

Contemporary advancement and digitalization of technology has made analysis of ink extremely challenging. Selecting the best technique for ink analysis is the need of the hour. The latest version of Video spectral comparator i.e. VSC®- 8000/HS has a vast horizon of features such as multi-spectral light sources, database of currencies and passports of different countries and even micro-spectrometer for composition analysis. The present study focuses on determining the efficacy and capability of light sources of varied spectrum and spectrometer for the examination of black ball, gel and fountain pen inks particularly in questioned under scrutiny written with hand. VSC®-8000/HS have demonstrated to be substantially efficient, robust and an exhaustive nondestructive technique for analysis of documents serving as evidence which have been manipulated including obliterations, additions or overlapping of two or more black ball or fountain pen inks. However, the technique did not provide effective results for black gel pen inks in contrast to black ball and fountain pen inks. Nonetheless, it can effectively harmonize with the standard workflow of a forensic document examiner to ensure qualitative and quantitative facts and figures for the expert testimony.

PLS-DA and infrared spectroscopy based rapid and non-destructive discrimination of black ball and gel pen inks for forensic application

In the Questioned Document, the examination of ink is crucial scientific evidence to discern the difference between genuine and forged documents. The document examination which is examined by physical and chemical analysis of ink involves the matching of the source of writing material used to fabricate the document of ink. In this study, fifty black ink samples (25 ball-point and 25 gel-point pens) are used. These ink samples are analyzed with Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy conjoined with chemometric method i.e. Principal Component Analysis (PCA) and PLS-Discriminant Analysis (PLS-DA). The spectroscopic discrimination is determined by the absence or presence of particular peaks or bands in the fingerprint region of black ink samples. The first-order derivative graphs are used for spectral characterization of ink samples. PCA reduces the dimensionality of large datasets into small number of independent Principal Components and increases interpretability but at the same time minimizes the data information loss. The utilization of the PLS-DA algorithm gives 100 % accuracy to differentiate two classes of black ink samples. The ROC curve value of the PLS-Discrimination Analysis model is 1 which means 100 % sensitivity and specificity. This non-destructive study is an analytical approach that helped to maintain the spectral library based on spectroscopic results of all fifty samples. The adequacy of the PLS-Discrimination Analysis model is checked by running a blind test of ten unknown samples.

Highly Efficient Photothermal Conversion of Ti3C2Tx/Ionic Liquid Gel Pen Ink for Smoothly Writing Ultrasensitive, Wide-Range Detecting, and Flexible Thermal Sensors.

Photothermal conversion behavior has a vital application to disease therapy, water purification, or uncontacted heaters. The fabrication of high-performance photothermal conversion materials especially for near-infrared (NIR) light and microstructures has attracted a great deal of attention. Among numerous substances, MXene as a new type of 2D material with semi-metallic and unique electromagnetic properties presents a broader absorption of light and even a typical plasmonic absorption near the NIR-I area (808 nm), which has made it suitable for photothermal conversion. Here, we propose a facile approach for preparing a Ti3C2Tx/ionic liquid ink with a high photothermal conversion efficiency. The as-prepared ink has showed good wettability of various substrates as well as the high sensitivity of 808 nm NIR light irradiation and a wide range of thermal variation. After packing the ink into a gel pen refill, the flexible thermal chips could be easily obtained just by pen writing on the soft surface with the designed size, which also have become an optimal candidate for the thermal alarm system.

Initial Study for the Determination of the Sequence of Intersecting Lines between Gel Pens and Seals by Optical Coherence Tomography.

Determining the sequence of intersecting lines is a significant issue in the forensic document examination that can reveal the fraud or distinguish between different allegations. Optical coherence tomography (OCT) is a high-resolution cross-sectional imaging technique that has been introduced into forensic science field recently. The potential of OCT as a novel method to determine the sequence of intersecting lines was examined for the first time. In this study, a spectral-domain OCT system with a center wavelength of 900nm was employed to perform nondestructive examination on determining the sequence of 18 heterogeneous intersecting line samples produced using three types of gel pens and three brands of stamp pad ink seals. Two-dimensional (2D) cross-sectional, and three-dimensional (3D) volumetric images of the intersecting lines were obtained by the OCT system. Several features were noted and analyzed to successfully determine the sequence of all the 18 samples. Blind tests were also conducted to demonstrate the effectiveness of OCT technique. The results illustrate that OCT technology can provide an effective and accurate method for sequencing intersecting lines of gel pen ink and seal ink, which may complement the conventional methods used in the examination of questioned documents.

Determination of the Chronological Order of a Laser Printing and Gel Pen Writing Without any Crossing Strokes

Laser printers and writing instruments are being exploited by the forgers to produce fabricated documents. They often produce such documents by appending genuine signature on a blank sheet and later printing on it. Often these fabricated documents do not contain intersection of strokes and may pose a difficulty to forensic document examiners in analyzing cases related to such documents. Keeping in mind the limited research work done on nonintersecting strokes, the present study has been conducted with an aim to determine the sequence of nonintersecting strokes of gel pens and laser printers. Three hundred samples of nonintersecting strokes of gel pen ink and laser printing were prepared. Of these 300, 150 had laser-printed text below the gel pen strokes and the remaining 150 were prepared with gel pen stokes below the laser-printed text. The samples have been analyzed using Nikon SMZ 800N stereomicroscope. Three micro-conformation features, that is, pattern of toner distribution, ink distribution, and fiber distribution have been observed in the samples. The results demonstrate the successful establishment of sequence of nonintersecting strokes in case of gel pen and laser-printed documents by the determination of micro-conformation features.

Establishing Sequence of Inkjet Printer, Laser Printer and Writing Ink Strokes using Scanning Electron Microscopy (SEM)

The aim of the present study is to determine the sequence of laser printer, inkjet printer, and writing ink (ball point pen ink, gel pen ink, pilot pen ink and fountain pen ink) strokes using a low voltage (1kV) scanning electron microscope (SEM). Intersections were prepared using an inkjet printer, laser printer, and writing instruments on copier paper. About 1cm2 of intersection was cut using scissors and mounted to the probe stage of the SEM using double-sided tape. Each sample was analyzed at different operating parameters. The results were evaluated on the basis of continuity and iscontinuity of strokes at intersection point. It was possible to determine the correct sequence of printer strokes versus other writing instruments’ strokes; inkjet printer stroke versus fountain and pilot pen ink stroke; however, inconclusive results were obtained in the case of inkjet printer strokes versus ball point pen and gel pen ink strokes. The ffectiveness of this technique was determined by analyzing the exact sequence of blind samples. An SEM could be used as mplimentary tool with other optical methods to examine the sequence of strokes.

Manufacture of a super-stable green gel pen ink based on CNC-indigo

Gel pens are the most popular writing instruments at present with the unique rheological properties for their excellent writing performance. It’s challenging to develop a super-stable gel pen ink, which is often manufactured based on complex ink components. In this paper, a new method was innovatively proposed to prepare a gel pen ink based on cellulose nanocrystals (CNC) and indigo. The effects of CNC concentration, storage temperature, acidity, alkalinity, and electrolyte content on the stability of the new CNC gel pen ink were investigated. When CNC concentration was between 3.81% and 7.08%, indigo usage was 1.5%, surfactant OP-10 dosage was 0.05%, the prepared new CNC gel pen ink exhibited good writing performance and super-stable dispersion stability. A little amount of acid, alkali and salt content would not impact the stability of the new CNC gel pen ink, which increased the feasibility of its industrial production and long-term storage or use.

Raman hyperspectral imaging and a novel approach for objective determination of the order of crossing ink lines.

The determination of the chronological order of crossing ink lines is a difficult problem in the examination of Questioned Documents. Modern methodologies are based on non-destructive chemical and physical analysis. However, the determination of the chronological sequence of crossing ink lines remains visual and subjective. This manuscript describes a study where Raman hyperspectral imaging is associated with different chemometric techniques and a novel method is applied for the objective determination of the chronological order of gel pen ink crossings. Eight blue and black gel pens of different brands were used to prepare 56 crossings on white paper. Raman mapping analyzed the entire crossing and the hyperspectral images were treated with k-means, Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS) and Partial Least Squares - Discriminant Analysis (PLS-DA). The order of crossings was determined visually and using a novel method that consisted in calculating the relative quantity of pixels of each ink in the crossing region that were equal or higher than an established threshold. Different thresholds were tested using mean and standard deviation. The MCR-ALS and the thresholds mean minus 1,96 of the standard deviation and the mean minus 2575 of the standard deviation determined correctly more than 70% of the crossings. This method proved to be more efficient than microscopy examination and more objective since no inconclusive determinations were obtained. The methodology is promising for entirely objective and highly effective determination of the chronological sequence of crossing ink lines.

Forensic Analysis of Gel Pen Inks using Hyperspectral Imaging coupled with Chemometric Procedures

Forensic examination of inks on questioned documents has becomean important practice and the law enforcement agencies rely heavilyon these techniques during criminal investigations. Although nowadaysthere are a variety of methodologies focused on the analysis of inks, thecombination of non-destructive nature of Hyperspectral Imaging (HSI)coupled with the multivariate chemometric technique has received littleattention.In this study, forty-five (n = 45) gel pen inks of three different coloursi.e. blue, red and black of five different brands were analysed usingHSI with the idea of classifying them according to the brand.In terms of discriminating similar coloured components betweensamples, this was achievable only on the basis of the % reflectancespectra. However, arguably, there was sufficient evidence to suggestthat it may be possible to discriminate the samples using chemometricof Principal Component Analysis (PCA). A 2-D score plot from PCAanalysis was enough to characterise the samples into five clusters.The synergy of complementary information provided by PCA narrowsmatching possibilities (in terms of classification) for forensic investigationsinvolving ink analysis.

Experimental Research on Class Identification with a New Type of Erasable Gel Pens.

A new type of erasable gel pen ink is becoming increasingly popular because of the modifiable characteristics for writing on documents. This study attempts to distinguish 12 types of blue and black erasable gel pens produced by mainstream stationery manufacturers using infrared (IR) visual analysis, Fourier transform infrared (FTIR) analysis, fluorescence analysis, and microspectrophotometry. The results demonstrate that IR visual, FTIR, and fluorescence analysis can be used to help distinguish each type of erasable gel ink. While microspectrophotometry can be used to effectively differentiate the blue gel inks in this study, there are limitations with respect to distinguishing black erasable gel pens. When these four optical analyses methods were used in combination, the gel inks could be accurately distinguished.

Statistical comparison of decision rules in PLS2-DA prediction model for classification of blue gel pen inks according to pen brand and pen model

Partial least squares-discriminant analysis (PLS-DA) is a favored modeling tool for high-dimensional data, e.g. infrared and Raman spectra. Prior to prediction, one needs to pre-select one decision rule (DR) for the PLS-DA model. The purpose of this work is to evaluate statistical differences of four novel DRs and the naïve DR in PLS2-DA prediction models for classification of blue gel pen inks based on attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra. The performances of the DRs have been estimated using forty sub-datasets that were prepared from the principal ATR-FTIR spectra. The global region together with three mutually exclusive spectral windows were preprocessed independently via nine different data preprocessing methods (i.e. mean centering, autoscaling, Pareto scaling, robust scaling, multiplicative scatter correction, normalization to sum, normalization to constant vector length, standard normal variate and asymmetric least squares). Then a series of 50 models (i.e. by including the first 50 PLS components incrementally) was constructed using the forty sub-datasets independently. Each model was evaluated using six different variants of v-fold cross-validation and external testing; and selected models were also assessed using iterative random sampling approach. Eventually, each DR was presented with a number of model estimates that describe the model accuracy and stability. Performances of the DRs were discussed according to summary statistics and ANOVA tests that were derived from the model estimates. Results show that the novel DRs are more accurate but relatively less stable than the naïve DR. The differences are statistically significant at the 0.05 significance level. In conclusion, both novel and naïve DRs are competitive with each other; and one has to decide on a trade-off between model stability and model accuracy.

Identification of volatile components of gel-pen inks through gas chromatography mass spectrometry

• About 245 components were detected in 90 colored gel pen inks using GC-MS. • Detected components were classified into alcohols, aldehyde and ketone, ester, ether, hydrocarbon and miscellaneous. • Few components found to be unique for specific ink color. • The major achievement of the study was the minimal consumption of sample, 4 ink strokes provided desired results.