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Corona, flame, atmospheric plasma, and liquid flame spray (LFS) techniques were used to create highly hydrophilic surfaces for pigment-coated paper and board and machine-glossed paper. All the surface modification techniques were performed continuously in ambient atmosphere. The physical changes on the surfaces were characterized by field emission gun-scanning electron microscopy (FEG-SEM), atomic force microscopy and Parker Print-Surf surface roughness. The chemical changes were analysed by X-ray photoelectron spectroscopy. The superhydrophilic surfaces, i.e. contact angle of water (CAW) <10°, were created mainly by modifying the surface chemistry of the paper and board by argon plasma or SiO2coating. The nano- and microscale roughness existing on paper and board surfaces enabled the creation of the superhydrophilic surfaces. Furthermore, the benefits and limitations of the surface modification techniques are discussed and compared. For example, the SiO2coating maintained its extreme hydrophilicity for at least six months, whereas the CAW of argon plasma-treated surface increased to about 20° already in one day. [ABSTRACT FROM AUTHOR]

A custom peel testing device has been developed to measure adhesion strength of flexible thin film layers. The device overcomes the inherent problems of traditional peel machines that are associated with inaccurate peel angle definition and complex sample clamping. To demonstrate its performance, we have compared peel adhesion of currently used paper-based and polymer-based banknotes. Polymer banknotes have shown higher peel strength, which may yield greater durability and ensure increased lifetime in intensive use during circulation. [ABSTRACT FROM PUBLISHER]

Directional mobility and controlled adhesion of water drops were obtained on superhydrophobic paper surfaces by generating high surface energy ink patterns using commercial desktop printing. By changing the curvature/shapes of the ink patterns, geometrical constraints were imposed on the movement of the three-phase liquid/solid/vapor contact line. With proper design of pattern shapes, the critical sliding angle of water drops was manipulated with respect to different directions. Adhesion tunability of water drops on superhydrophobic paper was established by design of chemical heterogeneity. Printing of 'checker' ink patterns with appropriate area fraction and feature dimensions allowed variation in the critical sliding angle of water drops. The manipulation of directional mobility and adhesion of water drops on superhydrophobic paper surfaces allows the design of novel components such as 2D flow paths, gates/diodes, junctions and drop size filters for emerging 2D paper-based microfluidics technology for biomedical diagnostic applications. [ABSTRACT FROM AUTHOR]

Inorganic fillers are inexpensive materials used to increase the density, smoothness and other properties of paper that are important for printing. In the current study, the adhesion of pressure-sensitive adhesives (PSAs), a common type of adhesive used in labels and tapes, to papers containing varying amounts and types of fillers is investigated. Papers with three types of fillers, precipitated calcium carbonate (PCC), ground calcium carbonate (GCC) and kaolin clay, were investigated. The compositions of the papers were examined with SEM/EDX, while peel and double cantilever beam (DCB) tests were used to assess PSA-paper adhesion. The results indicate that fillers enhance the adhesion between PSA and paper. In the case of the peel tests, a combination of inter-fiber bond strength and PSA-paper adhesion determines the peel strength. While in the DCB tests, failure is isolated to the PSA-paper interface, thus allowing measurements of pure interfacial failure. [ABSTRACT FROM AUTHOR]

Adhesion issues are present in many disciplines such as, for example, surface science, microrobotics or MEMS design. Within this framework, this paper presents a study on capillary forces due to capillary condensation. A simulation tool had already been presented using Surface Evolver and Matlab to compute the shape of a meniscus in accordance with the Kelvin equation and contact angles. The numerical results of this simulation complied well with literature results. One very important result is the ability to compute the evolution of the capillary force depending on the tilt angle of the gripper with respect to the object. The main contribution of this new paper is a test bench and the related experimental results which validate these numerical results. We present here new experimental results illustrating the role of humidity and tilt angle in capillary forces at the nanoscale. [ABSTRACT FROM AUTHOR]

Bioactive papers are advanced cellulose-based functional materials that incorporate biomolecules with specific recognition ability for analytes. Although there is a wide range of potential applications for these papers, only a few have reached the commercial stage. There are fundamental questions that have to be addressed before they can be developed in large scale. One of the central questions in bioactive paper development is the impact of the properties of the cellulosic support on both immobilization and functionality of biomolecules. This paper presents a literature review on inkjet printing of biomolecules for bioactive paper applications and reports recent progress made in understanding factors that affect the activity of enzymes physically immobilized on cellulosic supports. [ABSTRACT FROM AUTHOR]

Novel models are developed and previously published simple models characterizing the spreading of probe liquids and inks on solid surfaces are evaluated with water and ethylene glycol. The aim is to determine the most appropriate models which would be suitable to describe liquid and ink spreading on both chemically and structurally heterogeneous paper surfaces. The surface energy and its components (Lifshitz–van der Waals, acid and base) for the paper samples have previously been characterized at semi-equilibrium conditions. The equilibrium work of adhesion and work of spreading is found to be linearly related to the maximum print tack force of model inks. The dynamic spreading are found to be determined by coupled spreading mechanisms, being related both to the surface structure and surface chemistry. [ABSTRACT FROM AUTHOR]

We report the fabrication of a sticky superhydrophobic paper surface with extremely high contact angle hysteresis: advancing contact angle ∼150° (superhydrophobic) and receding contact angle ∼10° (superhydrophilic). In addition, we report the controlled tunability of the contact angle hysteresis from 149.8 ± 5.8° to 3.5 ± 1.1°, while maintaining superhydrophobicity, as defined through an advancing contact angle above 150°. The hysteresis was tuned through the controlled fabrication of nano-scale features on the paper fibers via selective plasma etching. The variations in contact angle hysteresis are attributed to a transition of the liquid–surface interaction from a Wenzel state to a Cassie state on the nano-scale, while maintaining a Cassie state on the micro-scale. Superhydrophobic cellulosic surfaces with tunable stickiness or adhesion have potential applications in the control of aqueous drop mobility and the transfer of drops on inexpensive, renewable substrates. [ABSTRACT FROM AUTHOR]

The interaction between paper and pressure-sensitive adhesive was investigated by peel adhesion testing. The paper/adhesive peel curves were analyzed by plotting the logarithm of the peak peel force (i.e. the maximum value) against the logarithm of the peel rate, yielding two linear segments: a peel-rate-dependent interfacial failure domain and a rate-independent paper failure domain. Three independent parameters were extracted from these plots, namely, the interfacial peel force (Fin) at a low peel rate of 1 mm/min, the maximum peel force (Fc) and the slope (Sp) in the plot of log (interfacial peel force) versus log (peel rate). The linkages between paper and its peel responses were analyzed using the multivariate statistical methods. The paper properties influencing peel force in interfacial failure domain were found to be primarily the paper surface chemistry, characterized by oxygen/carbon ratio (determined by XPS), and secondarily paper surface roughness. The peel force increased with oxygen/carbon ratio and with the surface roughness. The log–log slope in the interfacial failure domain was found to be independent of paper properties; it is determined by the adhesive rheology. The governing paper property in the paper failure domain was found to be the paper internal bond strength as measured by an internal (Scott) bond tester. [ABSTRACT FROM AUTHOR]

This paper discusses the use of etalons fabricated from prepared glass slides to quantify the dimensional stability of two adhesive materials in damp environments. This technique facilitated the screening of adhesives for a kinematically demanding application. In addition to describing the etalon technique, additional data are provided on the performance of the device with the selected adhesives. One of the adhesives is simply identified as a cationic cured adhesive, while the other adhesive was Loctite 3615. A range of adhesive bond gaps from 50 to 500 μm was examined for the adhesive that showed the least displacement resulting from environmental aging. The results of this testing were applied to a kinematically sensitive device for verification of the adhesives use in this geometry. [ABSTRACT FROM AUTHOR]

Peel experiments involving three PSA tapes and three paper substrates were employed to develop a general approach for the analysis of peeling from paper. Plotting the logarithm of the peak peel force (i.e. the maximum value) versus the logarithm of the peel rate yielded a generalized peel curve which illustrated transitions from interfacial to paper failure. The general peel curve consisted of linear segments (on the log/log plots) which intersected when the failure mode changed from interfacial to paper failure. The influence of paper type, PSA type, and peel angle on the generalized peel curve was determined. [ABSTRACT FROM AUTHOR]

A rapid-setting, starch-based lignocellulosic adhesive is described which could be cured at ambient temperature to form a film having a clear appearance and significant moisture resistance when tested under ambient conditions. Maltodextrins with a dextrose equivalent (DE) range of 5-25 were reacted as an intimate mixture in the dry state with N-methylolacrylamide (N-MAM) to give products containing the corresponding carbohydrate methyleneacrylamido ethers, which were characterized by NMR spectroscopy and electrospray mass spectrometry. The reaction products, comprising mixtures of maltodextrins and methyleneacrylamido ethers, were formulated in water for paper adhesive use and tested for performance. Paper strip peel tests showed a time to fibre tear of 2 min, an initial time to paper tear of 5 min, and 10 min to full paper adhesion. The failure load was 2.4 kN, diminishing to 1 kN after a 24 h cold water soak. [ABSTRACT FROM AUTHOR]