Thermochromic Ink Research Articles

Detection and imaging of thermochromic ink compounds in erasable pens using desorption electrospray ionization mass spectrometry.

Thermochromic ink pens are widely accessible worldwide and have gained popularity among the general public. These pens are very useful to undo mistakes while writing important documents or exams. They are also, however, misused in committing crimes such as counterfeiting checks or wills. Thus, the forensics community is in need of techniques that will allow these forgeries to be detected rapidly, reliably and conveniently. Thermochromic ink compounds were investigated using Desorption Electrospray Ionization (DESI) coupled with an LTQ mass spectrometer and Thin-Layer Chromatography (TLC). Tandem mass spectrometric analysis was conducted using Electrospray Ionization (ESI) coupled with an Orbitrap LTQ mass spectrometer performing Collision-Induced Dissociation (CID) for identification of ink traces. Chemical marker ions characteristic of the state of ink (visible or invisible) were identified and mapped in ink traces by the use of DESI-MS imaging. These ions can be employed by forensic experts as fingerprint markers in forged documents. The marker ions were also characterised by conducting tandem mass spectrometry using paper spray in an Orbitrap LTQ mass spectrometer. Specific chemical components yielding ions of m/z 400, 405, 615 and 786 were distinguished as only being apparent in the invisible and reappeared state of the ink. The absence of these compounds in the original state of the ink enabled their recognition as useful chemical determinants in detecting forgery. DESI-MSI was thus shown to be a very useful, convenient and reliable technique for detecting forgery in paper documents due to its fast and reproducible mode of analysis, with no sample preparation and minimal damage to the document under investigation. Copyright © 2017 John Wiley & Sons, Ltd.

Using thermochromic ink for medical simulations

© 2017 Alsalemi, Aldisi, Alhomsi, Ahmed, Bensaali, Alinier, Amira, licensee HBKU Press. This is an open access article distributed under the terms of the Creative Commons Attribution license CC BY 4.0, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. Alsalemi A, Aldisi M, Alhomsi Y, Ahmed I, Bensaali F, Alinier G, Amira A., 'Using thermochromic ink for medical simulations', Qatar Medical Journal, 4th Annual ELSO-SWAC Conference Proceedings 2017:63 http://dx.doi.org/10.5339/qmj.2017.swacelso.63

Deinkability of thermochromic offset inks

This paper evaluates the deinkability of thermochromic offset inks. For this purpose, three thermochromic inks were printed on white uncoated paper, in laboratory conditions. These prints were mixed in equal shares and recycled by means of chemical deinking flotation under defined conditions in the laboratory according to INGEDE method 11p. Deinkability is evaluated by calculating the flotation yield, pulp’s brightness and whiteness increase and the colour properties, determination of residual ink area, as well as ash content elimination. The obtained results indicate that thermochromic prints are poorly deinkable. The image analysis shows that flotation deinking managed to eliminate only 12.8% of the total dirt area of thermochromic ink. Only a small increase in deinked handsheets brightness and whiteness (approx. 5% and 2%) is noticed. The results of surface properties determination showed that the adhesion of inks on the paper is high. Thermochromic inks can affect wastewater too, by affecting its colouration due to their interactions with deinking solution and/or as a result of their mechanical damage during defibration.

Direct and contactless electrical control of temperature of paper and textile foldable substrates using electrospun metallic-web transparent electrodes.

Multiple and complex functionalities are a demand nowadays for almost all materials, including common day-to-day materials such as paper, textiles, wood, etc. In the present report, the surface temperature control of different types of materials, including paper and textiles, was demonstrated by Joule heating of metallic-web transparent electrodes both by direct current and by RF induced eddy currents. Polymeric submicronic fiber webs were prepared by electrospinning, and metal sputtering was subsequently performed to transform them into flexible transparent electrodes. These electrodes were thermally attached to different substrates, including paper, textiles and glass. Using thermochromic inks, we demonstrated a high degree of control of the substrates’ surface temperature by means of the Joule effect. Metallic fiber webs appear to be excellently suited for use as transparent electrodes for controlling the surface temperature of common materials, their highly flexible nature being a major advantage when dealing with rough, bendable substrates. This kind of result could not be achieved on bendable substrates with rough surfaces such as paper or textiles while employing classical transparent electrodes i.e. metal oxides. Moreover, contactless heating with induced currents is a premiere for transparent electrodes and opens up a score of new application fields.

Thermochromic tissue-mimicking phantom for optimisation of thermal tumour ablation

Purpose The purpose of this study was to (1) develop a novel tissue-mimicking thermochromic (TMTC) phantom that permanently changes colour from white to magenta upon heating above ablative temperatures, and (2) assess its utility for specific applications in evaluating thermal therapy devices.Materials and methods Polyacrylamide gel mixed with thermochromic ink was custom made to produce a TMTC phantom that changes its colour upon heating above biological ablative temperatures (> 60 °C). The thermal properties of the phantom were characterised, and compared to those of human tissue. In addition, utility of this phantom as a tool for the assessment of laser and microwave thermal ablation was examined.Results The mass density, thermal conductivity, and thermal diffusivity of the TMTC phantom were measured as 1033 ± 1.0 kg/m3, 0.590 ± 0.015 W/m.K, and 0.145 ± 0.002 mm2/s, respectively, and found to be in agreement with reported values for human soft tissues. Heating the phantom with laser and microwave ablation devices produced clearly demarcated regions of permanent colour change geographically corresponding to regions with temperature elevations above 60 °C.Conclusion The TMTC phantom provides direct visualisation of ablation dynamics, including ablation volume and geometry as well as peak absolute temperatures within the treated region post-ablation. This phantom can be specifically tailored for different thermal therapy modalities, such as radiofrequency, laser, microwave, or therapeutic ultrasound ablation. Such modality-specific phantoms may enable better quality assurance, device characterisation, and ablation parameter optimisation, or optimise the study of dynamic heating parameters integral to drug device combination therapies relying upon heat.

Functional and physical outcomes following use of a flexible CO2 laser fiber and bipolar electrocautery in close proximity to the rat sciatic nerve with correlation to an in vitro thermal profile model.

This study compared functional and physical collateral damage to a nerve when operating a Codman MALIS Bipolar Electrosurgical System CMC-III or a CO2 laser coupled to a laser, with correlation to an in vitro model of heating profiles created by the devices in thermochromic ink agarose. Functional damage of the rat sciatic nerve after operating the MALIS or CO2 laser at various power settings and proximities to the nerve was measured by electrically evoked nerve action potentials, and histology of the nerve was used to assess physical damage. Thermochromic ink dissolved in agarose was used to model the spatial and temporal profile of the collateral heating zone of the electrosurgical system and the laser ablation cone. We found that this laser can be operated at 2 W directly above the nerve with minimal damage, while power settings of 5 W and 10 W resulted in acute functional and physical nerve damage, correlating with the maximal heating cone in the thermochromic ink model. MALIS settings up to 40 (11 W) did not result in major functional or physical nerve damage until the nerve was between the forceps tips, correlating with the hottest zone, localized discretely between the tips.

Performative interactions between body and dress: thermochromic print in fashion

This research explores clothing as interactive tools using dynamic print in relation to garment construction. The research was conducted with four series of garments, produced with leuco dye-based thermochromic inks, tested in an arranged photo session in a semi-public space. The first two series were constructed and printed to create patterns in a rather uncontrolled and random way. In the third and fourth series of garments, the relationship between both conventional print and dynamic print and garment construction were specifically designed to expose parts of the body commonly associated with nudity in traditional western societies. The research showed a possible increase by the wearer in the third and fourth series of garments due to the interactive exposure of the model's body; this was facilitated by the dynamic print in combination with the construction of the garment, which acted inwards, towards the wearer, as a result of its outward expression.

Dynamic Ornament: An Investigation of Responsive Thermochromic Surfaces in Architecture

This paper describes the use of environmental sensor data as a basis for the design of architectural ornament that takes on a distinctive appearance in response to the atmospheric conditions where it is located. Among the goals of the project were the identification of inexpensive fabrication methods that could be used to build responsive surfaces at the scale of a room, and the identification of material and tectonic strategies for integrating dynamic information displays in buildings. A series of prototypes were constructed to explore the benefits and limitations of thermochromic ink as a material for visualizing dynamic data, and a method is proposed for building thermochromic surfaces based on printed circuit boards (PCB's) that is cost-effective and allows the fabrication of large surfaces through tiling. The limitations of this method include high power consumption, a short lifespan and difficulties in controlling the surface temperature.

Light fastness and high‐temperature stability of thermochromic printing inks

Thermochromic printing inks are known for their low stability under the influence of various external conditions, but the consequences of the phenomenon on dynamic colorimetric properties have not yet been analysed. In this work, thermochromic prints were exposed to light and heated at two different temperatures, 150 and 200 °C, for varying time periods. The changes to the dynamic colour properties of the samples were described. It was found that both exposure to light and heating to high temperatures degrade the dynamic properties of thermochromic inks; however, they have different effects on the colour hysteresis. The corresponding loops contract with light exposure and heating, which is best described by the area of the entire colour loop. Exposure to light broadens the corresponding loop, while heating makes it narrower. The chemical stability of inks after exposure was also analysed by forced oxidation applying weakly ionised oxygen plasma. Stability of thermochromic samples is a combined effect of the binder, the polymeric shell and the active core inside the pigment capsules. The results show that poor stability against light and high temperatures has different origins.

Demonstration of Thermodynamics and Kinetics Using FriXion Erasable Pens

FriXion erasable pens contain thermochromic inks that have colored low-temperature forms and colorless high-temperature forms. Liquid nitrogen can be used to kinetically trap the high-temperature forms of the ink at temperatures at which ordinarily the low-temperature forms are more thermodynamically stable.

Picture-to-picture switching in full-color thermochromic paper displays

Presently, we contemplate the merger of paper and electronics in different forms. There is a great desire to further explore this twinning of the information displaying features of printed papers and electronic inks. Here, we report a full-color paperboard display technology comprised of thermochromic and static inks combined with a patterned heater foil. Black and full-color thermochromic ink dots were screen-printed adjacent to, and on top of, static ink dots using a zero-angle mesh and template pattern orientation. As the heater is turned on and off, the display alter its content in between two predefined four-color pictures.

Dynamic colorimetric properties of mixed thermochromic printing inks

Leuco dye‐based thermochromic inks reversibly change from the coloured to the discoloured state in a defined, comparatively wide temperature region. Inside this region, the colour of a sample depends on the temperature and thermal history, which is known as the hysteresis effect. The colour of such a sample as a function of temperature has the shape of a hysteresis loop. Commercially available thermochromic inks have different loops, narrow or broad, and their shapes range from approximately symmetric to highly asymmetric. These properties are also important in mixtures of inks. The hysteresis loop of a mixture reveals its binary nature if the individual pure inks have well‐separated hysteresis. When inks with close‐separated loops, i.e. with similar activation temperatures, are mixed together, the loop of the mixture fuses together into an apparently single loop. Our research shows that some of their dynamic colour properties could be predicted in advance. However, optic and colorimetric properties of mixtures are not additive.

Colorimetric properties of reversible thermochromic printing inks

The colorimetric properties of three, leuco dye-based thermochromic inks at 31 °C activation temperature were studied. The inks had similar pigment particle size distribution and comparably thick microcapsule shells with similar stability against oxygen plasma etching. The colour of the inks was dependent on temperature as well as the thermal history of the sample, which gives rise to colour hysteresis. The area of the observed hysteresis loop in CIELAB colour space determines how different colours appear on the sample when decolourisation and colourisation processes are compared. The largest colour difference achieved for the same sample that arose because of different thermal history and temperature were determined. Four characteristic temperatures were ascribed to the two chemical reactions causing colour hysteresis. The stability of the decolourised state at cooling <activation temperature was confirmed as >10 h. The reversibility of the thermochromic effect diminished approximately linearly with the highest heating temperature.

Electrically controlled colour-changing textiles using the resistive heating properties of PEDOT nanofibers

Conductive PEDOT nanofiber mats were obtained by the electrospinning of oxidant fibers and subsequent vapour-phase polymerization of the EDOT monomer. The mats presented high conductivities as well as unprecedented resistive heating properties. Electrically controlled colour-changing textiles were produced by coating thermochromic inks on the PEDOT mats and triggering the colour change by applying current to the mat.

Thin, lightweight, foldable thermochromic displays on paper

This article describes an electronic display that is fabricated by patterning electrically conductive wires (heaters) with micron-scale dimensions on one side of a sheet of paper, and thermochromic ink on the opposite side. Passing electrical current through the wires heats the paper and changes the thermochromic ink from colored (black, green, or other colors) to transparent; this change in property reveals the paper underneath the ink-exposing any messages printed on the paper-and serves as the basis for a two-state "shutter" display. This type of display is thin (100 microm), flat, lightweight (the display weighs <20 mg/cm(2)), can be folded, rolled, twisted, and creased while maintaining function, and ultimately can (if required) be disposed of by incineration. The display is appropriate for applications where information must be presented clearly (usually only once) for little cost (each display costs <$0.10/m(2) in materials) and where limited electrical power is available.

Flexible dot-matrix display manufacture by offset lithography

Novel thermochromic graphic displays manufactured by printing thermochromic ink films in conjunction with conductive lithographic films (CLFs) are presented. Work in formulating lithographic printing inks is described. The properties of the deposited ink films and demonstration display structures employing these materials are discussed. These low-cost printed structures could be incorporated in the manufacture of electronic systems with integrated printed power sources affording environmental benefits when compared with conventional manufacturing techniques.

Atom-sensitive textiles as visual indicators for plasma post-discharges

The efficiency of surface treatments by plasma and post-discharge plasma processes is greatly dependent on the density of active species, such as neutral atoms in post-discharges. Therefore, many diagnostics exist to detect the presence and measure the concentrations of these species, but they often require expensive instrumentation and highly qualified personnel. These conditions are not often met when the process is industrially used and it becomes important to imagine simple indicators allowing to validate that the correct operating conditions are reached. In the present paper, we present the first results on the investigation of an inexpensive and easy to use visual indicator able to quantify the atomic species density in nitrogen post-discharge plasma processes. It is based on the differential recombination coefficients of N-atoms on metallic/textile fibres which are intrinsically bonded together in a fabric matrix which serves as support for a thermochromic ink. The specific heating of the metallic fibres by N-atom recombination heats the whole of the fabric, leading to a visible colour change of the thermochromic ink, and therefore, of the indicator. Through modelling, it was possible to estimate that the inclusion of copper fibres to a pure cotton matrix leads to a 60% increase of the global N-atom recombination coefficient of the fabric, sufficient enough to provide a clearly visible colour change.

Self-thermostatting organically coated steel cladding using thermochromic materials

This paper explores the effect of colour and gloss on the solar/thermal gain achieved by organically coated steels (OCSs) under external and artificial exposure conditions. External and artificial exposure tests have shown that the colour of an organic coating has a dramatic effect on the thermal gain. Otherwise identical black and white panel assemblies have been found to experience average thermal gains of 16 K and 1·6 K, respectively, over a typical UK daylight exposure. The coating gloss also affects the solar gain but to a much less significant level, with the thermal gain for standard panel colours changing by only 2·5 K when gloss levels are altered between 80 and 10%. Thus, the colour of the organic coating was the most important factor controlling thermal gain. To control solar gain, novel panel assemblies have been prepared in which thermochromic inks with two temperature dependent colours have been incorporated with an OCS topcoat. These have been compared with traditional OCS products, with similar colour and gloss to the two extremes of colour of the novel material. It has been found that as the temperature of the test panels rises and the colour of the organic coating is converted to its lighter shade, the thermal gain of the panel assemblies is lowered and thus the panels have a self-thermostatting capability.