Interfacial Area Ratio Research Articles

Do all ceramic and composite CAD-CAM materials exhibit equal bonding properties to implant Ti-base materials? An Interfacial Fracture Toughness Study

ObjectivesTo compare the interfacial fracture toughness (IFT) with or without aging, of four different classes of CAD-CAM ceramic and composite materials bonded with self-adhesive resin cement to titanium alloy characteristic of implant abutments. MethodsHigh translucent zirconia (Katana; KAT), lithium disilicate-based glass-ceramic (IPS. emax.CAD; EMX), polymer-infiltrated ceramic network material (PICN) (Vita Enamic; ENA), and dispersed filler composite (Cerasmart 270; CER) were cut into equilateral triangular prisms and bonded to titanium prisms with identical dimensions using Panavia SA Cement Universal. The surfaces were pretreated following the manufacturers’ recommendations and developed interfacial area ratio (Sdr) of the pretreated surfaces was measured. IFT was determined using the Notchless Triangular Prism test in a water bath at 36 °C before and after thermocycling (10,000 cycles) (n = 40 samples/material). ResultsIFT of the materials ranged from 0.80 ± 0.25 to 1.10 ± 0.21 MPa.m1/2 before thermocycling and from 0.71 ± 0.24 to 1.02 ± 0.25 MPa.m1/2 after thermocycling. There was a statistical difference between IFT of CER and the two top performers in each scenario: KAT and EMX before aging, and KAT and ENA after aging. Thermocycling significantly decreased IFT of EMX. The Weibull modulus of IFT was similar for all materials and remained so after thermocycling. Sdr measurements revealed that ENA (7.60)>Ti (4.97)>CER (2.85)>KAT (1.09)=EMX (0.96). SignificanceDispersed filler CAD-CAM composite showed lower performance than the other materials. Aging only affected IFT of Li-Si glass-ceramic, whereas zirconia and PICN performed equally well, probably due to their chemical bonding potential and surface roughness respectively.

Application of the Taguchi method to areal roughness-based surface topography control by waterjet treatments

Pure waterjet surface treatment without abrasive particles has a promising application in the biomedical field, because it induces compressive residual stresses on a metal surface and never leaves the tiny hard particles. In this work, the influence of operation pressure, standoff distance and the number of paths of the waterjet on the surface topography as well as the hardness was studied using the Taguchi method. The results showed that the most essential parameter is the operation pressure. By tuning the operation pressure from 100 to 300 MPa, the surface of Ti6Al4V specimens can be smoothed, roughened or damaged; when the surface layer is eroded, the new-born surface exhibits a clear stochastic nature accompanied by microvoids. The standoff distance benefits finer controlling the height parameters, whilst the number of paths affects the waviness. The hardening effect generated by the waterjet impingement extends to a few hundred-micron depth of the specimens, and the peak value of microhardness was found at a depth of 70 μm, which is an increase by greater than 20 %. The roughness parameters of Arithmetical mean height (Sa), Skewness (Ssk), Auto-correlation length (Sal), and Developed interfacial area ratio (Sdr) as a set are recommended to characterize the biomaterial's surface. The present research results promote the application of waterjet treatment in the field of fine-tuning biomaterial surface morphology.

Study on the influence of water ingress on the interface of high strength zinc coated steels and epoxy adhesives

This study aimed to assess the impact of humidity on adhesive joints comprising four different Zn-coated high strength steel substrates (SA, SB, SC, and SD) and two epoxy adhesives (EA and EB) at 70 °C. Several tests were conducted to analyse the effects of humidity on adhesive properties, under both dry and saturated conditions. Gravimetric tests were used to measure water absorption by the adhesives, while mechanical properties were evaluated through bulk tensile tests. Chemical structure changes were examined using Fourier-transform infrared spectroscopy (FTIR), and the glass transition temperature was determined using a DMA-like test. The water immersion behaviour of the substrates was studied through gravimetric tests and surface energy was analysed using contact angle measurements. The overall joint performance was assessed through gravimetric tests, and the mechanical impact of water was evaluated using single lap joint tests on both dry and aged joints, for one week and one month. The findings indicated that EB adhesive absorbed more water compared to EA, which did not reach saturation. FTIR analysis revealed significant chemical degradation in the EB adhesive after ageing, leading to greater deterioration in mechanical properties compared to EA. The bulk substrate tests showed similar surface energy among the substrates, with SA being the only substrate that did not corrode during water immersion. In terms of joint behaviour, cohesive failure was predominant in dry conditions, but as the joints aged, those with EB adhesive experienced a decrease in failure load due to adhesive degradation, while the interface remained strong. Joints with EA adhesive exhibited increasing interfacial failure, indicating weaker interfaces that allowed water ingress between the adhesive and substrate. Consequently, water uptake in the joints was higher for EA adhesive than for EB adhesive, contrary to the behaviour observed at the bulk level. SA and SD substrates demonstrated stronger interfaces with EA, likely due to their higher developed interfacial area ratio, which facilitated mechanical interlocking.

Reducing moisture ingress in flexible sensors with laser patterned polyimide

Polymeric materials that can more effectively act as barriers to environmental factors such as moisture are of significant interest to the sensor fabrication industry. Moisture ingress may corrode metallic traces or cause the decohesion of bonded interfaces of flexible sensors. Often, imparting a higher degree of moisture resistance necessitates encapsulating the sensors or applying specialty coatings. In this study, a laser patterning process is used to modify standard polyimide coverfilms used in flexible sensor manufacturing. The study achieved patterned polyimide surfaces in the partial wetting Cassie-Baxter regime which displayed reduced moisture diffusivity compared to the original polyimide surface by an order of magnitude. These surfaces displayed periodic structures with deep channels, a high developed interfacial area ratio, and a low contact angle. A laser-patterned sensor that makes use of this coverfilm-enhancing technique is demonstrated. Avoiding the need to apply additional moisture resistant films and instead laser patterning existing coverfilms could provide significant benefits to the flexible sensor industry, simplifying the fabrication of more robust sensors that are less prone to environmental degradation.

A study of the effect of laser micro-texture on bond strength and fracture mechanism of paint layer

As the most common protective layer in car body protection, the paint layer is an effective barrier against corrosion of the material matrix. The adhesion between the paint layer and the substrate is an important factor in ensuring the long-term and effective protection of the paint layer. On the 5083 aluminium alloy substrate, a series of laser micro-texture with varying depths are produced by laser texturing, with the aspect ratio ranging from 0.12 to 1.76. The adhesion test of standard GB/T 5210–2006 was used to investigate the effect of different texturing depths on the adhesion strength of the paint layer. The cross-sectional microstructure and fracture morphology of the paint layer were analysed and characterized to study the deposition and fracture mechanism of the paint layer. The results show that the presence of laser micro-texture significantly enhances the adhesion of the paint layer, and the influence of laser micro-texture of different depths and dimensions on the adhesion of the paint layer is different. And found that the optimal depth size affecting the size of adhesion is around 0.67. By analyzing the cross-sectional microstructure and fracture morphology of the paint layer, it is found that the change in paint adhesion is the result of the change of developed interfacial area ratio (Sdr), the bonding condition of the paint layer and the substrate surface, and the bubble defect. At the same time, the process of the paint layer flowing on the substrate surface, filling the micro-texture, and forming bubbles was analysed.

Increasing Heat Transfer from Metal Surfaces through Laser-Interference-Induced Microscopic Heat Sinks.

With the increasing processing power of micro-electronic components and increasing spatial limitations, ensuring sufficient heat dissipation has become a crucial task. This work presents a microscopic approach to increasing the surface area through periodic surface structures. Microstructures with a periodic distance of 8.5 µm are fabricated via Direct Laser Interference Patterning (DLIP) on stainless steel plates with a nanosecond-pulsed infrared laser and are characterized by their developed interfacial area ratio. The optimal structuring parameters for increasing the surface area were investigated, reaching peak-to-valley depths up to 12.8 µm and increasing surface area by up to 394%. Heat dissipation in a natural convection environment was estimated by measuring the output voltage of a Peltier element mounted between a hot plate and a textured sample. The resulting increase in output voltage compared to an unstructured sample was correlated to the structure depth and developed interfacial area ratio, finding a maximum increase of 51.4%. Moreover, it was shown that the output voltage correlated well with the structure depth and surface area.

Effects of interface microstructure on adhesion of polyetheretherketone metallized by titanium cold spray

Titanium powders were cold sprayed onto polyetheretherketone (PEEK) to investigate the effects of interface microstructure on bonding. Process guidelines to achieve adherent metallic deposits via cold spray onto thermoplastics are scarce, and mechanisms for metal adhesion onto thermoplastic substrates are unclear. The formation of a transition layer where deposition changes from metal-on-polymer to metal-on-metal deposition can promote adhesion but requires a clearer understanding. The microstructural features of such transition layers provide insights into mechanisms that promote coating adhesion. Select features, including developed interfacial area ratio and gradation of thermal residual stress, correlated to adhesive strength values. The understanding of interlocking mesoscale features formed during cold spray informs the parameter selection for depositing metals onto thermoplastics with strong adhesion.

Effect of Different Forms of Fluoride Application on Surface Roughness of Rhodium-Coated NiTi Orthodontic Wires: A Clinical Trial.

Objectives: This study aimed to assess the effect of different forms of fluoride application on surface roughness of rhodium-coated nickel-titanium (NiTi) orthodontic wires. Materials and Methods: This randomized clinical trial was conducted on 15 patients randomly divided into three groups: toothbrush with Oral-B toothpaste only, Oral-B toothpaste, and daily mouthwash, Oral-B toothpaste, and sodium fluoride gel. The surface roughness indices of orthodontic wires including arithmetic mean height (Sa), root mean square height, root mean square gradient, developed interfacial area ratio (Sdr) and maximum surface height were measured by atomic force microscopy at baseline and after 6 weeks of application in the patients' mouths. Data were analyzed by paired t-test, ANOVA, Games-Howell, and Tukey-HSD tests (P<0.05). Results: All surface roughness parameters in all three groups showed a significant increase after intervention, except for Sa in the toothpaste-only group (P=0.057) and Sdr in the sodium fluoride gel group (P=0.064). Conclusion: The surface roughness of rhodium-coated NiTi orthodontic wires increases following the use of different forms of fluoride.

Ultrafast Laser Patterning of Metals Commonly Used in Medical Industry: Surface Roughness Control with Energy Gradient Pulse Sequences

Ultrafast laser ablation is widely used as a versatile method for accurate micro-machining of polymers, glasses and metals for a variety of industrial and biomedical applications. We report on the use of a novel process parameter, the modulation of the laser pulse energy during the multi-scan texturing of surfaces. We show that this new and straightforward control method allows us to attain higher and lower roughness (Ra) values than the conventional constant pulse energy irradiation sequence. This new multi-scanning laser ablation strategy was conducted on metals that are commonly used in the biomedical industry, such as stainless steel, titanium, brass and silver samples, using a linear (increasing or decreasing) gradient of pulse energy, i.e., varying the pulse energy across successive laser scans. The effects of ablation were studied in terms of roughness, developed interfacial area ratio, skewness and ablation efficiency of the processed surfaces. Significantly, the investigation has shown a global trend for all samples that the roughness is minimum when a decreasing energy pulse sequence is employed, i.e., the irradiation sequence ends up with the applied laser fluences close to threshold laser fluences and is maximum with increasing energy distribution. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis on single craters with the three different energy deposition conditions revealed a chaotic and random material redistribution in the cases of uniform and increasing energy distributions and the presence of regular laser-induced periodic surface structures (LIPSS) at the bottom of the ablation region in the case of decreasing energy distribution. It is also shown that the ablation efficiency of the ablated surfaces does not significantly change between the three cases. Therefore, this novel energy control strategy permits the control of the roughness of the processed surfaces without losing the ablation efficiency.

2D Surface Roughness Quantification for Enhanced Petrophysical Applications

Summary Surface roughness is an essential rock parameter affecting petrophysical properties that are surface sensitive such as characterization of pore structure and wettability. For instance, Wenzel’s contact angle formula for rough surfaces requires knowledge of the surface roughness, and surface roughness is expected to speed up the aging of cores in crude oil for wettability restoration. In addition, proper quantification of surface roughness is critical for obtaining representative, roughness-independent, pore sizes for applications such as prediction of permeability and interpretation of capillary pressure curves. Intuitively, a surface is better characterized in 2D than in 1D. This 2D study is a continuation and enhancement of the previous 1D work, recently published in the SPE Journal (Ma et al. 2021). In this current paper, a comprehensive investigation of 1D vs. 2D surface roughness measurements is conducted to evaluate and cross validate the two approaches. In this study, surface roughness is measured on 26 carbonate rock samples by laser scanning confocal microscopy (LSCM), where both the 1D absolute increment surface roughness, Sr, and the 2D interfacial area ratio of surface roughness, Sdr, are reported. As expected, the results indicate that surface roughness characterized by 2D Sdr has a greater dynamic range than the 1D Sr measurement, i.e., the 2D Sdr provides a more representative characterization of surface roughness. A detailed account of methodologies, assumptions, limitations, validation, and applications of the 1D and 2D surface roughness characterization is documented in this paper. To extract the roughness features present on rock grain surfaces, effects of de-spiking and filter length, used to eliminate pore-size effects, are investigated. For specific applications of surface roughness corrected pore-size estimation from nuclear magnetic resonance (NMR) measurements, differences in length scales of surface roughness are compared between LSCM measurement and that derived from NMR diffusion-T2 plus BET (Brunauer-Emmett-Teller) surface area. The surface roughness-corrected NMR pore-size distribution is also validated against the pore-size distribution obtained from the measurement of micro-computed tomography (CT) scanning.

Area difference between monolayers facilitates budding of lipid droplets from vesicles.

Lipid droplets (LDs) are intracellular organelles that play a central role in cellular lipid balance and energy homeostasis. Though extensive experimental studies have been carried out on LD biogenesis, relatively little is known about the mechanical interaction between LDs and vesicles, and in particular effects of area difference between vesicle leaflets on LD evolution are not theoretically rationalized. Here we theoretically explore how the monolayer area difference regulates the budding and morphological evolution of an LD embedded in the vesicle membrane. It is shown that both the monolayer area difference and interfacial energy strength, attributed to the LD-membrane contact, facilitate the LD budding with the confined LD evolving from a bulge to a spherical protrusion. The budding direction is towards the monolayer with more phospholipids. Outward and inward budding phase diagrams are established with respect to the interfacial energy strength and area ratio between the outer and inner monolayers. Moreover, the osmotic pressure of the vesicle promotes the LD budding at a small monolayer area difference and inhibits the budding at a relatively large monolayer area difference.

Evolution of Electroplated Cubic Boron Nitride Tool Surface Texture Parameters During Point Grinding

Abstract Point grinding is an abrasive machining process that utilizes small diameter superabrasive single-layer grinding tools for accurate machining of complex 3D geometries. Due to the small nature of these tools, high wear-rates and uneven wear around the tool circumference present a challenge for their successful application for the finish machining of metallic components. It is, therefore, essential to monitor the surface condition of the point grinding tools, to ensure their safe and reliable operation. In this investigation, the 3D topography evolution of single-layer B126 cubic boron nitride (cBN) point grinding tools was characterized using focus-variation imaging. Given the wealth of information obtained using this method, a decision-matrix methodology was used to identify the most important parameters for monitoring the wear condition of the point grinding tools. Grinding trials were also performed with fixed cutting parameters and varied cutting durations up to 520 mm3 of material removed to assess the evolution of the point grinding tool surfaces over time as a result of wear during grinding of hardened D2 tool steel. The best criteria for the characterization of the surface texture of electroplated cBN point grinding tool surfaces were identified to be the average surface height (Sa), skewness (Ssk), root mean square gradient (Sdq), reduced peak height (Spk), peak material volume (Vmp), and developed interfacial area ratio (Sdr). These parameters performed best for direct measurement of point grinding tool surfaces, paving the way for the application of the imaging technique under manufacturing conditions as an on-machine monitoring method for performance assessment.

Improving the Separation of PS and ABS Plastics Using Modified Induced Air Flotation with a Mixing Device

A dramatic increase in plastic waste has resulted in a strong need to increase plastic recycling accordingly. A selective flotation has been highlighted due to its outstanding efficiency for the separation of mixed plastics with analogous physicochemical characteristics. In this study, the effects of design and operational factors on the bubble’s hydrodynamic and mixing parameters in induced air flotation (IAF) with a mixing device were investigated through a design of experiment method (DOE) analysis for improving the plastic separation efficiency (i.e., PS and ABS). As a result of DOE analysis, the increase in the induced air tube diameter together with the rotational speed could generate a smaller bubble size. This led to the enhancement of the ratio of interfacial area to velocity gradient (a/G), which was interestingly found to be a significant factor affecting plastic recovery apart from the chemical agents. It demonstrates that operating IAF with a mixing device at a greater a/G ratio improved the plastic separation performance. These findings suggest that operating an IAF process with a mixing device at suitable a/G conditions could be a promising technique for separating plastic wastes, which have similar physicochemical characteristics as PS and ABS.

Three-Dimensional Nanoscale Morphological Surface Analysis of Polymeric Particles Containing Allium sativum Essential Oil.

Biodegradable particles were developed using poly-ε-caprolactone and gelatin carriers containing different concentrations of Allium sativum essential oil (EO) (360 µg/mL, 420 µg/mL, and 460 µg/mL). Atomic force microscopy was useful to evaluate the particles’ surface based on morphological parameters. The particles’ size varied from 150 nm to 300 nm. The diameter was related to the increase of the particles’ height as a function of the EO concentration, influencing the roughness of the surface core values (from 20 to 30 nm) and surface irregularity. The spatial parameters Str (texture aspect ratio) and Std (texture direction) revealed low spatial frequency components. The hybrid parameters Sdq (root mean square gradient) and Sdr (interfacial area ratio) also increased as a function of the EO concentration, revealing fewer flat particles. On the other hand, the functional parameters (inverse areal material ratio and peak extreme height) suggested differences in surface irregularities. Higher concentrations of EO resulted in greater microtexture asperity on the particles’ surface, as well as sharper peaks. The nanoscale morphological surface analysis allowed the determination of the most appropriate concentration of encapsulated EO, influencing statistical surface parameters.

Improved energy efficiency and surface quality in medium-density fibreboard (MDF) sanding process by applying precision-shaped grits

ABSTRACT Abrasive belt sanding is essential to medium-density fibreboard (MDF) manufacturing and application. To achieve an energy-efficient machining with better surface quality, a kind of abrasive belt with precision-shaped grits (PSG) was applied in this study. As a contrast, an ordinary abrasive belt with random fractured grits (RFG) was taken into account. The surface morphology of each belt was compared and analyzed to see the difference. The power used to remove per unit mass of workpiece material (P*s) was measured and calculated. When the belt speed reached 12.08 m/s, the P*s of PSG belt was 28.5% lower. The micrographs of sanded MDF surfaces generated by PSG belt and the related interfacial area ratio (Sdr) indicated less ploughed area. Besides, the average values of Ra, Rz, Rq and RSm for the surface sanded by PSG belt were significantly lower. The obtained findings could provide new perspectives in MDF sanding operations considering MDF surface creation mechanism with new abrasive tools.

Ti-6Al-4V/SUS316L dissimilar joints with ultrahigh joint efficiency fabricated by a novel pressure-controlled joule heat forge welding method

Ti-6Al-4V/SUS316L dissimilar joints were manufactured by a novel solid-state joining method named “pressure-controlled joule heat forge welding”. The microstructure and mechanical properties of the joints were systematically investigated. Both materials were homogeneously deformed by applying the pressure corresponding to the intersectional point of the temperature-dependent yield strength. Along the joint interface, the uniform hardness distributions in the center and periphery regions were obtained because the heat input generated by the joule heat was homogeneous from center to periphery. The welding temperature was able to be decreased to suppress the formation of the intermetallic compound (IMC) layers by applying the high pressure because the welding is accompanied and accomplished by the interfacial deformation and the high pressure affects the deformable temperature. As a result, when the applied pressure was increased from 300 MPa to 450 MPa, the width of the IMC layers was decreased to around 28 nm. As the upset increased, the interfacial area ratio to base material increased hence the interfacial defects were successfully suppressed, and the tensile strength increased by removing the ragged surface and the oxide layers existing on the surface of the base material. Eventually, the joint efficiency reached 98.5 % compared to the base material.

Removal of basic fuchsine dye using (TiO2/MWCNTs) nanomaterial

In this study, antase-type titanium dioxide (TiO2) was produced and mixed with multi-walled carbon nanotubes using an ultrasonic. To aid the mixing process, ethanol was employed as a dispersing solvent. The nano titanium dioxide was loaded onto multi-walled carbon nanotubes for prepared (TiO2/MWCNTs). Thestructuralcharacteristicsofananocomposite(TiO2/MWCNTs)wereinvestigated(FTIR, XRD, AFM, SEM, EDX). The (TiO2 Anatase) was discovered to have a 15.65 nm average particle size. The (TiO2/MWCNTs) nanocomposite had a composition of (0.75TiO2/0.016MWCNTs) (w/w), which resulted in an increase in the developed interfacial area ratio from (159.07%) for (TiO2) to (210.3%) for (TiO2/MWCNTs). Batch adsorption tests were used to assess the efficacy of utilizing (TiO2/MWCNTs) to remove basic fuchsin dye from aqueous solution. With increasing contact time, the amount of dye removed by the adsorbent increased, and optimal adsorption was reached in 40 min. The adsorption process was affected by the pH of the aqueous solution, with the best dye removal happening at pH = 6. The adsorbent's ability to absorb dye decreased as the original dye concentration and adsorbent dose increased. Adsorption equilibrium data was fitted with Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin equations to describe the isotherms. The Freundlich and Temkin models performed better than the Langmuir and Dubinin-Radushkevich models in describing the experimental results. The pseudo-first and second order models were used to fit the kinetic data. The Pseudo-second-order model suited the data better than the Pseudo-first-order model. The maximum rate of removal is approximately 98 percent. Thermodynamic studies revealed that the adsorption was exothermic. Out of five distinct temperatures, the free energy of adsorption (Δ G°) was found to be −35.35 kJ.mol-1 at 25 °C. The fact that (Δ G°) was negative indicated the technique's viability and the spontaneous nature of adsorption.

Peeling mechanism of interlocked interface between etched acrylonitrile-butadiene-styrene and electroplated metal layer

Electroplating of metals on polymer materials is one of the best decorative processes for achieving low cost and light weight. However, low interfacial adhesion often limits practical utilization due to the potential peel-off behavior of metal layers. The interface between the metal layers and acrylonitrile-butadiene-styrene (ABS) substrate and its peeling mechanism are investigated as a function of etching time. Sa, the arithmetic average roughness of the unit area, and Sdr, the interfacial area ratio, are adopted instead of linear roughness, Ra, to quantify the surface profile. As the etching time increases, both Sa and Sdr for the etched ABS and corresponding metal side increase. The failure mode changes from adhesive to cohesive as the etching time increases, and the peel-off strength of the electroplated ABS exhibits a dependence on the tensile strength of the substrate. The peel-off strength of the electroplated ABS specimens increases to 8.46 N/cm after 30 min of etching time, but the interface degrades, forming inner voids. The Sdr ratio (Sdr, polymer / Sdr, plating) is proposed as a surface parameter to predict the peel-off strength of electroplated ABS and represents a new attempt to quantitatively correlate the interfacial morphology with the adhesion strength.

Focus variation technology as a tool for tissue surface characterization

The surface of tissue paper is relatively complex compared to other paper grades and consists of several overlapping structures like protruding fibres, crepe and fabric-based patterns at different spatial frequencies. The knowledge of tissue surface characteristics is crucial when it comes to improvement with respect to surface softness and the perceptual handfeel of tissue products. In this work we used the optical based, non-contact measurement principle of focus variation for surface characterization of dry-creped, textured and through air dried (TAD) tissue. Based on the three tissue grades, a procedure which includes the characterization of the whole tissue surface throughout different scales within one setup, was developed. Surprisingly, focus variation was rarely used in tissue-related research, as it provides robust and reliable 3D surface information which can be used for further areal surface analysis. Special attention was given to the preparation and discussion of the raw data up to the final analysis including several spatial filtering steps. Enhanced surface parameters like the developed interfacial area ratio (Sdr) and the power spectral density (PSD) were used to describe the surface adequately. The surface roughness of the three tissue grades was compared, with the textured tissue showing the highest roughness in Sdr and PSD analysis. Although both methods are based on different principles, a high correlation in terms of evaluated roughness is evident. Regular structures like crepe and patterns are obtainable as peaks at the respective frequency with a certain intensity in the PSD evaluation. Apart from topography in terms of structures and roughness, the wide field of view of the focus variation measurement also allows assessment of effects related to flocculation and sheet formation. The developed procedure could also be appropriate for other fibre based materials and/or fabrics, which are similar to tissue with respect to optical properties such as for example nonwovens.Graphic abstract

Application of Focus Variation Microscopy and Dissolution Imaging in Understanding the Behaviour of Hydrophilic Matrices.

Hydrophilic matrix systems can be found in a wide range of extended release pharmaceutical formulations. The main principle of these systems is that upon contact with water, the hydrophilic component swells to form a hydrated gel layer which controls drug release. The following work demonstrates an explorative study into the use of dissolution imaging and focus variation microscopy with hydrophilic polymers. This study investigated the surface properties of xanthan gum (XG), polyethylene oxide (PEO), and hypromellose (hydroxypropyl methylcellulose, HPMC) compacts with each of these three hydrophilic polymers from one of each classification of natural, semi-synthetic, or synthetic polymer using a focus variation instrument. The auto correlation length (Sal) showed all surface profiles from the compacts displayed a value below 0.1 mm, indicating that only high frequency components (i.e., roughness) were considered and that the analysis had been successful. The developed interfacial area ratio (Sdr) displayed values below 5% in line with ISO guidelines for all the polymers studied with their texture aspect ratio values (Str) > 0.5, indicating uniformity of the surfaces of the produced compacts. Of the various parameters studied, areal material ratio (Smr2) predicted XG to wet and hydrate quicker than PEO, with PEO also wetting and hydrating quicker than the HPMC. The dissolution imaging and initial swelling studies proved to concur with the findings from the areal material ratio (Smr2) parameter, suggesting porosity was not an indicator for the ease with which water ingress occurs. This study suggests the Smr2 surface parameter to potentially predict wetting and initial hydration of hydrophilic polymers, however care should be taken as this study consists of a selected number of hydrophilic polymers.