Infinite Focus Research Articles

Manufacturing and Test of Split and Recombine Micromixers with a Variable Cross-Section

The methodology for manufacturing array of microdevices that features a varying cross-section is introduced towards the development of complex devices that are more prone to be adapted in-field. In this paper stereolithography or digital light, processing is assessed for developing asymmetric split-and-recombine micromixers that can be tested under a machine vision system. To test the proposed manufacturing methodology an array of 6 microdevices with a varying depth from 100 to 1000 micrometers were characterized using an Infinite Focus Measurement to verify the feasibility of the proposed methodology for a large range of length-to-depth ratios. Surface metrology showed that molds were produced within 4 to 10 mm of absolute deviational error. Split and Recombine (SAR) micromixers devices were manufactured employing microfabrication methods derived from the semiconductor industry to engrave polydimethylsiloxane (PDMS) such as photolithography, or to a lesser extent micromachining or laser ablation of other materials. However, these methodologies have several limitations; they are often expensive, require special infrastructure such as clean rooms and may have long production cycles for new designs. Moreover, devices are manufactured using a soft lithography technology that is limited to a singular cross-section depth. An Envisiontec Perfactory P3 Mini Multilens additive manufacturing equipment that uses a 60 mm lens system and with a work tray of 84 x 63 x 230 mm and with a pixel resolution of up to 50 μm for the used material. The equipment was loaded with a white Flex Series ABS resin characterized by a yield stress of 65MPa and a Young's modulus of 1772 MPa. An Otoflash pulse curing chamber from the same supplier with a wavelength between 300 and 700 nanometers, with a lamp of 11 watts of power and 10 pulses per second. An array of six assymetric asymmetric SAR micromixers (ASAR) were developed with a width of 1000 µm and a varying depth of 100, 250, 500, 750, 900 and 1000 µm for depth-to-width ratio of 1:10, 1:4, 1:2, 3:4, 9:10 and 1:1 respectively. For characterization of the molds, an Alicona Infinite Focus Measurement Machine has been employed for surface characterization. This device allows the acquisition of datasets at a high depth of focus similar to a Scanning Electronic Microscope. Infinite Focus Microscopy (IFM) has shown to be capable of capturing images with a lateral resolution down to 400 nm providing 3D datasets with very accurate results. For this work, each mold depth array element was measured twice for a total number of 36 samples. The molds were used to pour polydimethylsiloxane (PDMS) to produce the micromixing structures. A syringe pump and two plastic syringes were used to individually supply fluorescent particles and a solution of blue dye and distilled water through the micromixer inlets at same flow rate. A flow rate of 1 ml/min was applied to the microdevice to test the device sealing. Two machine vision setups were employed: an inverted microscope with a ultra high-speed camera and an inverted microfluidic microscope were implemented to evaluate used to assess the performance of a micromixer using the concentration field including parameters such as mean concentration (Cm), standard deviation (σ), coefficient of variation (CoV) or mixing index (M). Methodology for the production of an array of micromixers with a variable cross-section in a single step was successfully implemented. Figure 1

Development of a preclinical natural porcine knee simulation model for the tribological assessment of osteochondral grafts in vitro

In order to pre-clinically evaluate the performance and efficacy of novel osteochondral interventions, physiological and clinically relevant whole joint simulation models, capable of reproducing the complex loading and motions experienced in the natural knee environment are required. The aim of this study was to develop a method for the assessment of tribological performance of osteochondral grafts within an in vitro whole natural joint simulation model.The study assessed the effects of osteochondral allograft implantation (existing surgical intervention for the repair of osteochondral defects) on the wear, deformation and damage of the opposing articular surfaces. Tribological performance of osteochondral grafts was compared to the natural joint (negative control), an injury model (focal cartilage defects) and stainless steel pins (positive controls). A recently developed method using an optical profiler (Alicona Infinite Focus G5, Alicona Imaging GmbH, Austria) was used to quantify and characterise the wear, deformation and damage occurring on the opposing articular surfaces. Allografts inserted flush with the cartilage surface had the lowest levels of wear, deformation and damage following the 2 h test; increased levels of wear, deformation and damage were observed when allografts and stainless steel pins were inserted proud of the articular surface. The method developed will be applied in future studies to assess the tribological performance of novel early stage osteochondral interventions prior to in vivo studies, investigate variation in surgical precision and aid in the development of stratified interventions for the patient population.

Investigation of infinite focus microscopy for the determination of the association of blood with fingermarks

The determination of the type of deposition mechanism of blood within fingermarks at the scene of violent crimes is of great importance for the reconstruction of the bloodshed dynamics. However, to date, evaluation still relies on the subjective visual examination of experts. Practitioners encounter three types of scenarios in which blood may be found in fingermarks and they refer to the following three deposition mechanisms: (i) blood marks, originating from a bloodied fingertip; (ii) marks in blood, originating from a clean fingertip contacting a blood contaminated surface; (iii) coincidental deposition mechanisms, originating from a clean fingertip contacting a clean surface, leaving a latent fingermark, and subsequent contamination with blood. The authors hypothesised that, due to differences in distribution of blood in the furrows and on the ridges, the height of blood depositions on the ridges and furrows (and their relative proportions), will differ significantly across the three depositions mechanisms. A second hypothesis was made that the differences would be significant and consistent enough to exploit their measurement as a quantitative and objective way to differentiate the deposition mechanisms.In recent years, infinite focus microscopy (IFM) has been developed, allowing for the computational generation of a 3D image of the topology of a sample via acquisition of images on multiple focal planes. On these bases, it was finally hypothesised that the application of this technique would allow the distinction of deposition mechanisms (i) to (iii). A set of preliminary experiments were designed to test whether IFM was “fit for purpose” and, subsequently, to test if any of the three deposition mechanisms scenarios could be differentiated. Though IFM enabled the analysis of tape lifted samples with some success, for samples produced and analysed directly on the surface of deposition, the results show that the measurements from any scenario will be highly dependent on the original surface of deposition (both in terms of its nature and of the variable exposure to environment); as crime scenes exhibit a wide range of possible relevant surfaces of deposition, the technique showed to not have the desired wide appeal for inclusion into a standardised set of protocols within a routine crime scene workflow.

Struktury uzasadniania. Część I. Infinityzm i koherentyzm

This paper is the first part of a series of articles about the structure of justification. I outline the so-called infinite regress problem and focus on three corresponding positions: skepticism (concerning justification), infinitism, and coherentism. Skepticism found its expression in Agrippa’s trilemma. Infinitism has been developed by Peter Klein and Scott Aikin. Coherentism is (primarily) discussed in its holistic version. I present different concepts of coherence and coherent justification, point out the main objections to coherentism and some ways to rebut them. General considerations concerning coherentism are illustrated by solutions included in the theories of Laurence BonJour and Thomas Bartelborth.

Defects in Friction Stir Welding of Steel

Defects associated with friction stir welding of two steel grades including DH36 and EH46 were investigated. Different welding parameters including tool rotational and tool traverse (linear) speeds were applied to understand their effect on weld seam defects including microcracks and voids formation. SEM images and infinite focus microscopy were employed to identify the defects types. Two new defects associated with the friction stir welding process are introduced in this work. The first defect identified in this work is a microcrack found between the plunge and the steady state region and attributed to the traverse moving of the tool with unsuitable speed from the plunge-dwell to the steady state stage. The tool traverse speed has recommended to travel 20 mm more with accelerated velocity range of 0.1 from the maximum traverse speed until reaching the steady state. The maximum recommended traverse speed in the steady state was also suggested to be less than 400 mm/min in order to avoid the lack in material flow. The second type of defect observed in this work was microcracks inside the stirred zone caused by elemental precipitations of TiN. The precipitates of TiN were attributed to the high tool rotational speed which caused the peak temperature to exceed 1200 °C at the top of the stirred zone and based on previous work. The limit of tool rotational speed was recommended to be maintained in the range of 200-500 RPM based on the mechanical experiments on the FSW samples.

Parametric and nonparametric description of the surface topography in the dry and MQCL cutting conditions

This paper focuses on the parametric and nonparametric description of surface topography after turning in the dry and MQCL conditions. The carried out research involved the longitudinal turning tests of duplex stainless steel, conducted in a range of variable cutting speeds vc and feeds f. Surface topography measurements were conducted with the application of Infinite Focus G4 microscope. In the first stage of research, the parametric analysis of the machined surfaces has been conducted. It included the evaluation of amplitude surface roughness parameters. In the next stage the nonparametric description of machined surfaces was carried out. This analysis has been focused on the presentation of machined surfaces in the form of contour maps and isometric images. The last stage of experiment involved the evaluation of surface isotropy and formulation of material ratio charts. The conducted research shows that the application of MQCL method can lead to the reduction of 3D surface roughness parameters compared to values reached after the dry machining. Moreover, the better distribution of irregularity peaks and pits under the MQCL method, comparing to that obtained after dry cutting implies that surfaces machined with the use of MQCL technique can be characterized by a high wear resistance.

Thermo-Mechanical Effect on Poly Crystalline Boron Nitride Tool Life During Friction Stir Welding (Dwell Period)

Poly Crystalline Boron Nitride (PCBN) tool wear during the friction stir welding of high melting alloys is an obstacle to commercialize the process. This work simulates the friction stir welding process and tool wear during the plunge/dwell period of 14.8 mm EH46 thick plate steel. The Computational Fluid Dynamic (CFD) model was used for simulation and the wear of the tool is estimated from temperatures and shear stress profile on the tool surface. Two sets of tool rotational speeds were applied including 120 and 200 RPM. Seven plunge/dwell samples were prepared using PCBN FSW tool, six thermocouples were also embedded around each plunge/dwell case in order to record the temperatures during the welding process. Infinite focus microscopy technique was used to create macrographs for each case. The CFD result has been shown that a shear layer around the tool shoulder and probe-side denoted as thermo-mechanical affected zone (TMAZ) was formed and its size increase with tool rotational speed increase. Maximum peak temperature was also found to increase with tool rotational speed increase. PCBN tool wear under shoulder was found to increase with tool rotational speed increase as a result of tool’s binder softening after reaching to a peak temperature exceeds 1250 °C. Tool wear also found to increase at probe-side bottom as a result of high shear stress associated with the decrease in the tool rotational speed. The amount of BN particles revealed by SEM in the TMAZ were compared with the CFD model.

Simple geometry tribological study of osteochondral graft implantation in the knee.

Robust preclinical test methods involving tribological simulations are required to investigate and understand the tribological function of osteochondral repair interventions in natural knee tissues. The aim of this study was to investigate the effects of osteochondral allograft implantation on the local tribology (friction, surface damage, wear and deformation) of the tissues in the natural knee joint using a simple geometry, reciprocating pin-on-plate friction simulator. In addition, the study aimed to assess the ability of osteochondral grafts to restore a low surface damage, deformation and wear articulation when compared to the native state. A method was developed to characterise and quantify surface damage wear and deformation of the opposing cartilage-bone pin surface using a non-contacting optical profiler (Alicona Infinite Focus). Porcine 12 mm diameter cartilage-bone pins were reciprocated against bovine cartilage-bone plates that had 6 mm diameter osteochondral allografts, cartilage defects or stainless steel pins (positive controls) inserted centrally. Increased levels of surface damage with changes in geometry were not associated with significant increases in the coefficient of dynamic friction. Significant damage to the opposing cartilage surface was observed in the positive control groups. Cartilage damage, deformation and wear (as measured by change in geometry) in the xenograft (2.4 mm3) and cartilage defect (0.99 mm3) groups were low and not significantly different (p > 0.05) compared to the negative control in either group. The study demonstrated the potential of osteochondral grafts to restore the congruent articular surface and biphasic tribology of the natural joint. An optical method has been developed to characterise cartilage wear, damage and deformation that can be applied to the tribological assessment of osteochondral grafts in a whole natural knee joint simulation model.

In vitro study of white spot lesion: Maxilla and mandibular teeth.

AimThe aim of the study was to evaluate the effect of resin infiltration on colour changes and surface roughness of artificial white spot lesions (WSLs) on maxillary and mandibular premolar.Materials and methodsSixty (60) extracted sound Maxilla (Mx) and Mandibular (Mn) premolars were randomly divided into 2 groups (test and control). Artificial WSLs were produced on buccal surface of teeth and were immersed in artificial saliva for 8 weeks. Colour components (L∗, a∗, b∗) and surface roughness (Sa∗) were assessed on 40 teeth using colour difference meter RD-100 and Alicona® Infinite Focus profilometer respectively. The measurements were done at baseline (T1), directly after artificial WSLs (T2), after 24 hours immersed in saliva and application of resin (T3) and immersion in artificial saliva for 1 (T4), 2 (T5), 4 (T6), 6 (T7) and 8 (T8) weeks. SEM images analysis were carried out on 20 teeth in four time points.ResultsThe values of L∗ (lightness), b∗ (yellow/blue) and Sa∗ (surface roughness) are gradually reduced to the baseline value. Whereas, the value of a∗ gradually increased with distinct treatment time to achieve the baseline value. The higher value of L∗ and Sa∗, the whiter the lesion suggesting higher degree of enamel demineralization and surface roughness. Lower L∗ values suggest a masking colour effect.ConclusionThe material produced favorable esthetics on colour and the surface roughness of teeth at distinct treatment times. It is recommended to be used to improve WSL post orthodontic treatment.

INCREASING THE QUALITY OF DRILLING HOLES IN FIBER REINFORCEMENT COMPOSITE MATERIALS

Problems. Fiber reinforcement polymer composite materials (FRP) are used in many areas of modern machine building, mostly in aircraft and aerospace industries. Millions of high-quality holes in FRP details are necessary for production of a modern passenger aircraft, to provide reliable bolt and rivet connections. Drilling is a key-machining operation for the production of holes in FRP.Comparing metal-containing materials drilling, FRP drilling is accompanied by the appearance of specific defects, such as delamination, uncut fibers, the damages of FRP’s matrix from the holes surface and thermal destruction. The listed defects adversely affect the reliability of bolt and rivet joints between parts of FRP, which determines the relevance of this study.The aim of the study. Determination of the influence of the support cutting edges of the developed drill with superhard materials on the holes surfaces quality of carbon fiber reinforcement plastics (CFRP) samples.Research methodology. The goals were achieved by experimental investigations on drilling CFRP samples by the designed drill bits and drill bit from SECO (Sweden) with similar cutting conditions. The drilling process was accompanied by the registration the axial force of cutting, torque and the acoustic emission signal. The analysis of the registered signals allowed to study the features of support cutting edges of the developed drill. The quality of the drilled holes surfaces was analyzed by determining the roughness using Alicona Infinite Focus (Austria) optical microscope. Conclusions were made according to the results of experimental studies.Conclusions. Analyzed data are shown, that the developed drill provides twice the lower roughness of the holes surfaces than the drill SECO, according to the same level of the wear of the main cutting edges. These results are mainly due to the work of the support cutting edges of the developed drill on a reversing feed.

Flushing Enhancement with Vibration and Pulsed Current in Electrochemical Machining

This research aims to understand flushing of by-products in electrochemical machining (ECM) by modeling and experimentally verifying mechanism of particle transport in inter-electrode gap under low frequency vibration. A series of hole were drilled on steel plates to evaluate the effect of vibration on material removal rate and hole quality. Infinite focus optical technique was used to capture and analyze the three-dimensional images of ECM'ed features. Experimental results showed that maximum machining depth and minimum taper angle can be achieved when vibrating the workpiece at 40 Hz and 10 µm amplitude. Simulation results showed that the highest average flushing speed of 0.4 m/s was obtained at this vibration frequency and amplitude. Machining depth and material removal rate has a positive correlation with the average flushing speed. Sharper ECM’ed profile is obtained since the taper angle is favorably reduced at high average flushing speed.

Friction Stir Welding of EH46 Steel Grade at Dwell Stage: Microstructure Evolution

This work aims to understand the effect of changes in friction stir welding (FSW) process parameters on the resulting microstructure specifically the effect of the plunge depth and tool rotational speed, during the “dwell” period on the resulting microstructure. A series of (FSW) of 14.8-mm-thick EH46 steel plate using a hybrid polycrystalline boron nitride FSW tool with spindle speeds of 120 and 200 revolutions per minute have been produced with increasing plunge depths from 0.1 to 0.7 mm. Thermocouples embedded around the top surface of each plunge case were used to measure the peak temperature during the process. The plunge depths were measured using the infinite focus microscopy, and the microstructure of all the heat affected regions was investigated extensively by scanning electron microscopy. It was found that phase transformation is sensitive to the variation on plunge depth. Small increase in plunge depth caused a significant change in the microstructure. Increasing tool rotational speed was also found to cause a significant difference in the microstructure.

Investigation of Coated Cutting Tool Performance during Machining of Super Duplex Stainless Steels through 3D Wear Evaluations

In this study, the wear mechanisms and tribological performance of uncoated and coated carbide tools were investigated during the turning of super duplex stainless steel (SDSS)—Grade UNS S32750, known commercially as SAF 2507. The tool wear was evaluated throughout the cutting tests and the wear mechanisms were investigated using an Alicona Infinite Focus microscope and a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). Tribo-film formation on the worn rake surface of the tool was analyzed using X-ray Photoelectron Spectroscopy (XPS). In addition, tribological performance was evaluated by studying chip characteristics such as thickness, compression ratio, shear angle, and undersurface morphology. Finally, surface integrity of the machined surface was investigated using the Alicona microscope to measure surface roughness and SEM to reveal the surface distortions created during the cutting process, combined with cutting force analyses. The results obtained showed that the predominant wear mechanisms are adhesion and chipping for all tools investigated and that the AlTiN coating system exhibited better performance in all aspects when compared with CVD TiCN + Al2O3 coated cutting insert and uncoated carbide insert; in particular, built-up edge formation was significantly reduced.

Variable-focus microscopy and UV surface dissolution imaging as complementary techniques in intrinsic dissolution rate determination

This work reports a novel approach to the assessment of the surface properties of compacts used in Surface Dissolution Imaging (SDI). SDI is useful for determining intrinsic dissolution rate (IDR), an important parameter in early stage drug development. Surface topography, post-compaction and post-SDI run, have been measured using a non-contact, optical, three-dimensional microscope based on focus variation, the Alicona Infinite Focus Microscope, with the aim of correlating the IDRs to the surface properties. Ibuprofen (IBU) was used as a model poorly-soluble drug. DSC and XRD were used to monitor possible polymorphic changes that may have occurred post-compaction and post-SDI run. IBUs IDR decreased from 0.033mg/min/cm2 to 0.022mg/min/cm2 from 10 to 20min, respectively, during the experiment. XRD and DSC showed no form changes during the SDI run. The surface topography images showed that a distinct imprint was embossed on the surfaces of some compacts which could affect IDRs. Surface parameter values were associated with the SDI experiments which showed strong correlations with the IDR values. The variable-focus microscope can be used as a complimentary tool in the determination of IDR values from the SDI.

Flexural Properties of Halloysite Nanotubes-Polyester Nanocomposites Exposed to Aggressive Environment

This study aimed to investigate the effect of aggressive environment on the flexural properties of halloysite nanotubes-polyester nanocomposites. Results showed that the addition of halloysite nanotubes into polyester matrix was found to improve flexural properties of the nanocomposites in dry condition and after water-methanol exposure. Significant increase in surface roughness was also observed and measured by Alicona Infinite Focus optical microscope.

Measurements of Surface Texture Parameters After Ultrasonic Assisted and Conventional Grinding of ZrO2 Based Ceramic Material Characterized by Different States of Sintering

The article presents the results of measurements of surface texture parameters after ultrasonic assisted grinding (UAG) and conventional grinding (CG) of ZrO2 based ceramic material. The machined samples are characterized by different states of sintering. Ultrasonic 20 linear machine tool and two different diamond grinding pins were applied to machine ceramic samples. Surface roughness measurements were performed and the values of parameters were computed using Infinite Focus Real 3D microscope (optical focus-variation technique) and 3D scanner Talyscan (contact measurement). The results of measurements were analyzed in order to state the influence of machining conditions on surface texture parameters.

Disturbances and noise: Defining furrow-form enamel hypoplasia.

The investigation of the record of growth locked in dental enamel provides a unique opportunity to build a comprehensive picture of growth disruption episodes during childhood. This study presents a new methodological basis for the analysis of enamel growth disruptions (enamel hypoplasia) using incremental microstructures of enamel. A three-dimensional technique based upon use of an Alicona 3D Infinite Focus imaging microscope and software is used to record developmental features in the enamel of human permanent mandibular lateral incisors of one individual from the Neolithic site of Çatalhöyük (Turkey). Using this new technique, perikymata are measured down the longitudinal axis of the crown from the incisal margin to the cervix and perikyma spacing profiles are constructed with this new technique. A mathematical basis for the detection of spacing anomalies, which serve as indicators of enamel hypoplasia is presented based upon these profiles. Three clearly delineated defects were identified visually, then matched and confirmed metrically using the enamel surface and perikyma spacing profiles. Human growth has often been used as an indicator of health in past societies because of developmental sensitivity to fluctuations in nutritional status and disease load. Hence, standardization of furrow-form defect identification is of crucial importance for reducing the amount of current subjectivity in the determination of a threshold for the identification of defects among individuals of past populations. The method presented here, which is based on microscopic images of the tooth crown as well as recorded measurements of incremental structures, represents a combined visual-metric approach using LOWESS residuals, and as such provides a substantial advancement to previous methods. It is therefore recommended that additional studies be carried out with this methodology to determine whether this method improves the reliability of enamel defect identification among individuals recovered from bioarchaeological contexts.

A technique to measure surface asperities plastic deformation and wear in rolling contact

Wear measurement of rolling contact during running-in is challenging because the mass loss is minor and the wear track change is almost undetectable. To overcome this limitation, wear is monitored by measuring the nano-scale deformation of the surface asperities of the roller in a rolling contact using the infinite focus microscope (IFM). An accurate surface image repositioning method is achieved between the initial profile and the subsequent profiles for each complete cycle. The image-processing technique for measuring the area and volume difference from the asperity profile is developed. Based on the constant volume principle, the volume attributed to the plastic flow is identified as the volume accumulated in the valley, and the wear volume is the difference between the volume of asperities removed and the volume of material accumulated in the valley. The wear volume measured using this technique can be as small as 514µm3, which is equivalent to 4 nanograms of mass loss for stainless steel material. The plastic volume ratio is measured and the trend is in good agreement with the plasticity index, proving that this technique can be used to explain the plastic deformation and wear mechanism during the running-in phase of the rolling contact.

Corrosion Behavior of Welded Joints for Cargo Oil Tanks of Crude Oil Carrier

E32 grade corrosion resistant steel was welded with welding wires with three different S contents. The microstructure, mechanical properties, inclusions, and corrosion behavior of welded joint were investigated. The joint coupon corrosion test and potentiodynamic polarization test were carried out under the simulated corrosion environment of the inner bottom plates of cargo oil tanks. The pitting initiation and propagation mechanism of the weld metal were studied by scanning electron microscopy and infinite focus. The results indicated that the microstructures of three kinds of weld metals are all composed of acicular ferrite, ferrite side-plate and proeutectoid ferrite. The microstructure of heat-affected zone is composed predominantly of bainite. Joint welded with low S filler wire has good mechanical properties. S can decrease free corrosion potential and increase the corrosion tendency. The pitting initiation is oxide inclusion or sulfide-oxide inclusion complex. S can induce the formation of occluded area and promote the corrosion propagation. The chemical compositions of weld metal is similar to base metal, which can limit the galvanic corrosion between weld metal and base metal, and avoid formation of corrosion step.

3-D modelling and statistical properties of surface pits of corroded wire based on image processing technique

A method based on image processing was proposed in this study to visualize and model surface pits of high-strength steel wire. Surface measurement based on infinite focus was employed to measure the pit depth all over the cylindrical surface. Corrosion pits were visually identified by a binary image with a greyscale threshold clustered by the optimal entropy threshold method. Ellipse approximation was simulated to precisely characterize individual corrosion pits, and the geometric and morphological parameters of the corrosion pits were calculated and statistically analysed. The proposed method provides an effective approach for 3D corrosion pit modelling.