Perpendicular Contact Research Articles

Exceptional anisotropic superhydrophobicity of sword-lily striated leaf surface and soft lithographic biomimicking using polystyrene replica

Herein, we report unusually high anisotropic superhydrophobicity, unidirectional self-cleaning, and biomimicking of adaxial sword-lily (Gladiolus hortulanus) leaf comprising three distinct levels of surface textures. Observably, the static anisotropic wetting and rolling of water droplets are more favourable in the parallel (or, striation) direction than in the perpendicular direction. Inspired from such water repellency of the sword lily leaf surface, here bio-mimicked polystyrene (PS) leaf construct is developed through a soft lithographic technique. Considering different water droplet sizes (4–10 μl) on natural lily leaf and bio-mimicked PS construct surfaces, the respective parallel (θ ||) and perpendicular (θ ⊥) water contact angles (WCAs) stand at, θ || ∼143°–147°, θ ⊥ ∼156°–169°; and θ || ∼130°–139°, θ ⊥ ∼142°–145°. Moreover, the specimens under study exhibit roll-off angles ranging, α || ∼8°–23° (α ⊥ ∼16°–41°) and α || ∼21°–49° (α ⊥ ∼40°–55°) along parallel (and perpendicular) directions; respectively. A noticeable difference in α ⊥ and α || values can be ascribed to the profound three-phase contact line (TCL) pinning along the perpendicular direction taking advantage of striation as means of barrier. The roll-off angles can also alter due to a variation in the droplet volume. The unusual anisotropic superhydrophobicity and unidirectional droplet roll-off can be attributed to the entrapped air within the micro-nano texture beneath the water droplet along with the pinning effect in the perpendicular direction caused by the striated heights.

Robust, high-density lesion mapping in the left atrium with near-infrared spectroscopy.

Radiofrequency ablation (RFA) procedures for atrial fibrillation frequently fail to prevent recurrence, partially due to limitations in assessing extent of ablation. Optical spectroscopy shows promise in assessing RFA lesion formation but has not been validated in conditions resembling those in vivo. Catheter-based near-infrared spectroscopy (NIRS) was applied to porcine hearts to demonstrate that spectrally derived optical indices remain accurate in blood and at oblique incidence angles. Porcine left atria were ablated and mapped using a custom-fabricated NIRS catheter. Each atrium was mapped first in phosphate-buffered saline (PBS) then in porcine blood. NIRS measurements showed little angle dependence up to 60deg. A trained random forest model predicted lesions with a sensitivity of 81.7%, a specificity of 86.1%, and a receiver operating characteristic curve area of 0.921. Predicted lesion maps achieved a mean structural similarity index of 0.749 and a mean normalized inner product of 0.867 when comparing maps obtained in PBS and blood. Catheter-based NIRS can precisely detect RFA lesions on left atria submerged in blood. Optical parameters are reliable in blood and without perpendicular contact, confirming their ability to provide useful feedback during in vivo RFA procedures.

The effect of ablation settings on lesion characteristics with DiamondTemp ablation system: An exvivo experiment.

Creating large lesion in ablations using the DiamondTemp (DTA) ablation system may reduce the frequency of arrhythmia recurrence and allow the treatment of ventricular arrhythmias. Therefore, this study aimed to investigate whether power, application time, contact force (CF), and contact angle affect lesion formation in the ventricles. Ablations were delivered to porcine myocardial preps to evaluate the lesion characteristics. Ablations were conducted with a maximum power of 50 W, target temperature of 58°C, CF of 10, 20, or 30 g, and contact angle between the catheter tip and tissue. The ablation durations were 15, 30, 60 s, 15 s × 2, or 30 s × 2. Steam pops occurred only in cases with perpendicular contact. The lesion depth was larger in all settings in the perpendicular orientation than in the parallel orientation. The temperatures were lower in all settings in the perpendicular orientation than in the parallel orientation. The lesions became larger as CF increased with perpendicular contact and duration of ≥30 s. The longer application time resulted in larger surface area, depth, and volume of the lesion. Lesion depth was greater with single application of 30 and 60 s than with 15 s × 2 and 30 s × 2, respectively. It is important to perform a single prolonged application as much as possible to create deeper lesions. Parallel contact with the tissue should be maintained to take advantage of the temperature sensor's capabilities to avoid pop phenomenon.

CFD-DEM numerical study on air impacted packing densification of equiaxed cylindrical particles

A CFD-DEM model was developed to reproduce the packing densification process of mono-sized equiaxed cylindrical particles under air impact. The effects of operating parameters on packing density were firstly studied. Then various microscopic properties of packing structures such as coordination number (CN), contact types, particle orientations, pore features were characterized and compared. And corresponding densification mechanisms were analysed based on particle motion behaviour, local structure evolution, and forces. Results indicate that the air impact can realize the packing densification of cylindrical particles under appropriate conditions. The pore size distribution in the packing of cylindrical particles shows a tail at larger pore sizes compared with that in the packing of equal spheres. Both the size and the sphericity of the pores decrease in the final dense packing; also, more surface-surface and less surface-edge contacts between two particles therein can be formed. More cylindrical particles tend to be in parallel or perpendicular contact with each other to form more stable local structures during air impact. Most particles at higher position move down (direction of gravity/air impact) with about one particle length during the densification process and most particles exhibit translational motion to realize the local rearrangement for pore filling through air impact induced inter-particle forces.

Predicting friction at the bone – Implant interface in cementless total knee arthroplasty

Cementless total knee arthroplasty (TKA) components have rough and porous surface coatings which can enhance bone ingrowth and stability at the bone-implant. To achieve primary stability in the postoperative period where no apposition is formed, the resistance against motions between bone and implant is optimized by increasing the friction at the interface. This is necessary, as excessive relative motions can inhibit bone ingrowth, which might result in loosening and pain. In this research, it was found that the friction can be predicted by measuring the surface morphology of rough implants, and calculating the corresponding perpendicular and lateral contact area parameters. The ratio between these areas, is used to predict the resulting coefficient of friction (COF). This is validated experimentally, by analysing the tribological behaviour of 2 porous and rough titanium coatings against human cadaveric knee bones using reciprocal friction tests with varying normal loads. The results for 2 different coatings showed similar findings for the predicted COF (0.75 and 0.88) versus the calculated values based on the measurement (0.82 and 0.86) proving the feasibility of the approach.

Impact of catheter contact angle on lesion formation and durability of pulmonary vein isolation

PurposeThis study is aimed to evaluate the impact of catheter contact angle on lesion formation and durability of pulmonary vein isolation (PVI).MethodsBoth in vitro experiment and retrospective observational study were conducted. For in vitro experiment, radiofrequency lesions were created on explanted swine hearts in three different catheter contact angles (0°, 45°, and 90°). In the retrospective observational study, we assessed patients who had undergone repeat catheter ablation due to atrial fibrillation recurrence after initial PVI. When pulmonary vein (PV) reconnection was observed, we analyzed the previous ablation points within and without the gap area. The gap areas were where ablation had changed the PV activation sequence or eliminated the PV potential in the repeat session.ResultsIn the in vitro experiment, lesion width was the smallest (5.3 ± 0.4 mm) in perpendicular contact compared to 0° (vs 5.8 ± 0.5 mm, p = 0.040) and 45° (vs 6.4 ± 0.4 mm, p < 0.001). In the retrospective observational study, we assessed 666 tags of 16 patients with PV reconnections, and 60 tags were in the gap area. Tags in the gap area had longer interlesion distance (odds ratio [OR] 1.49, p < 0.001), greater contact force variability (OR 1.03, p = 0.008), and higher rate of perpendicular contact (OR 3.26, p < 0.001) on multivariate analysis.ConclusionsPerpendicular contact was associated with a smaller lesion and higher rate of PV reconnection.

Mean curvature flow with linear oblique derivative boundary conditions

In this paper, we study the mean curvature flow with oblique derivative boundary conditions. We prove the longtime existence by choosing a suitable auxiliary function. Also, we prove the asymptotic behavior of the mean curvature flow with zero oblique derivative boundary data which is a generalization of Huisken’s original result about prescribed perpendicular contact angle.

Impact of Catheter Contact Angle on Lesion Formation and Durability of Pulmonary Vein Isolation

Objectives: This study aimed to evaluate the impact of catheter contact angle on lesion formation and durability of pulmonary vein isolation (PVI). Background: Little is known on the effect of catheter contact angle on lesion formation and durability of PVI. Methods: Both in vitro experiment and retrospective observational study were conducted. For in vitro experiment, radiofrequency lesions were created on explanted swine hearts in three different catheter contact angles (0{degree sign}, 45{degree sign}, and 90{degree sign}). In the retrospective observational study, we assessed patients who had undergone repeat catheter ablation due to atrial fibrillation recurrence after initial PVI. When pulmonary vein (PV) reconnection was observed, we analyzed the previous ablation points within and without the gap area. The gap areas were where ablation had changed the PV activation sequence or eliminated the PV potential in the repeat session. Results: In the in vitro experiment, lesion width was the smallest (5.3 {plus minus} 0.4 mm) in perpendicular contact compared to 0{degree sign} (vs 5.8 {plus minus} 0.5 mm, p=0.040) and 45{degree sign} (vs 6.4 {plus minus} 0.4 mm, p<0.001). In the retrospective observational study, we assessed 666 tags of 16 patients with PV reconnections, and 60 tags were in the gap area. Tags in the gap area had longer interlesion distance (odds ratio [OR] 1.49, p < 0.001), greater contact force variability (OR 1.03, p = 0.008), and higher rate of perpendicular contact (OR 3.26, p < 0.001) on multivariate analysis. Conclusion:Perpendicular contact was associated with a smaller lesion and higher rate of PV reconnection

Influence of relative density of the granular base soil on filter performance

Perpendicular contact erosion due to poorly designed filters is a frequent hazard for water-retaining structures serving as lifeblood to the community. This phenomenon occurs when the fine particles of a base soil at the contact interface with a coarser material are detached and transported through pores formed by the coarse particles. Therefore, most filter design criteria focus on the gradation of coarse particles or the gradation of pore constrictions. Meanwhile, the parameters of the base soil, such as relative density, are often overlooked. On the one hand, some experts neglect the impact of relative density because perpendicular contact erosion occurs at the interface, where fine particles expose themselves to larger pores. On the other hand, it is a general belief that the more compacted a base soil is, the less susceptible it will be to erosion as the seepage is reduced. This paper discusses this dilemma from a mutual perspective which assesses the influence of relative density from experimental, numerical, and analytical standpoints. The experimental study reveals that there is an optimal relative density which will release the least eroded mass. The influence is crucial as it can change the status of stability to unstable. The physical essence of the phenomenon is expressed by a numerical study at the micro-scale, which investigates the redistribution of flow lines and stress resulting from a particle detachment. The discovery at the micro-scale is confirmed by an analytical evaluation at the macro-scale, which assesses the redistribution of pore constrictions.

Droplet impingement and wetting behavior on a chemically heterogeneous surface in the Beyond–Cassie–Baxter regime

AbstractDroplet impingement and anisotropic wetting on chemically heterogeneous stripe‐patterned surfaces is simulated by means of many‐body dissipative particle dynamics. The ratio of the stripe width and initial droplet diameter, defined as β, ranges from 0.5 to 1.0 so that the wetting process is in the Beyond–Cassie–Baxter regime and is highly anisotropic. At zero Weber number (that is, without considering droplet inertia) and with superhydrophobic stripes, β is the only factor affecting the droplet perpendicular contact angle and aspect ratio. For inertial droplets, β and the Weber number are found to have an effect on the eventual droplet morphology on multi‐striped surfaces. These morphologies include elongated shape, split‐off, and “butterfly” shape. A correlation for critical split‐off conditions has been determined. An energy analysis of droplet impingement shows that the normalized surface energy of the droplet is independent of the Weber number if the droplet is elongated or butterfly‐shaped.

Combined local impedance and contact force for radiofrequency ablation assessment

The combination of contact force (CF) and local impedance (LI) may improve tissue characterization and lesion prediction during radiofrequency (RF) ablation. The purpose of this study was to evaluate the utility of LI combined with CF in assessing RF ablation efficacy. An LI catheter with CF sensing was evaluated in swine (n = 11) and invitro (n = 14). The relationship between LI and CF in different tissue types was evaluated invivo. Discrete lesions were created invitro and invivo at a range of forces, powers, and durations. Finally, an intercaval line was created in 3 groups at 30 W: 30s, Δ20Ω, and Δ30Ω. In the Δ20Ω and Δ30Ω groups, the user ablated until a 20 or 30 Ω LI drop. In the 30s group, the user was blinded to LI. Invivo, distinction in LI was found between the blood pool and the myocardium (blood pool: 122 ± 7.02 Ω; perpendicular contact: 220 ± 29 Ω; parallel contact: 207 ± 31 Ω). LI drop correlated with lesion depth both invitro (R = 0.84) and invivo (R = 0.79), informing sufficient lesion creation (LI drop >20 Ω) and warning of excessive heating (LI drop >65 Ω). When creating an intercaval line, the total RF time was significantly reduced when using LI guidance (6.4 ± 2 minutes in Δ20Ω and 8.1 ± 1 minutes in Δ30Ω) compared with a standard 30-second workflow (18 ± 7 minutes). Acute conduction block was achieved in all Δ30Ω and 30s lines. The addition of LI to CF provides feedback on both electrical and mechanical loads. This provides information on tissue type and catheter-tissue coupling; provides feedback on whether volumetric tissue heating is inadequate, sufficient, or excessive; and reduces ablation time.

Time-Dependent Anisotropic Wetting Behavior of Deterministic Structures of Different Strut Widths on Ti6Al4V

This study investigated the wetting behavior of Ti6Al4V surfaces that were groove-structured by means of femtosecond laser irradiation. The material was treated under ambient air conditions by use of a laser wavelength of 1030 nm and a pulse duration of 300 fs. Highly accurate structures with a gap width of 20 µm, a gap depth of 10 µm, and varying strut widths (1–300 µm) were generated and the contact angles in parallel and perpendicular direction were determined using sessile drop method with ultrapure water 1, 8, and 15 days after irradiation. All deterministic surfaces exhibited a pronounced contact angle change over time. The structures showed a strong anisotropic wetting behavior with a maximum contact angle aspect ratio of 2.47 at a strut width of 40 µm and a maximum difference between the parallel and perpendicular contact angle of 47.9° after 1 day.

Friction between single aramid fibres under pre-tension load

Abstract Understanding the friction mechanism at microscale of fibrous material is important as it is one of the key roles in governing the behaviour of fibre assemblies at meso and macroscale. However, mechanical stress such as tension may also influence the frictional behaviour. In this study the frictional behaviour between fibres under pre-tension is explored. A new experimental setup was successfully developed to measure the friction force between two single aramid fibres at perpendicular contact. Although pre-tension influences the bending stiffness of the fibre, the results show that the effect of pre-tension on the contact length is relatively small. The elastic deformation of the contact dominates over the ‘wrapping effect’, generating the contact area over which the interfacial shear takes place.

Measuring Liquid Drop Properties on Nanoscale 1D Patterned Photoresist Structures

This communication reports liquid wetting properties of DI-water on one-dimensional nano-patterned photoresist lines atop a silicon substrate as the pattern period is varied from 0.3- to 1.0-µm. Both constant photoresist height and constant width/height ratios are investigated. The line/period ratio was fixed at 0.3 (0.4) for different measurement sequences. The surface of the photoresist was treated with a short CHF3 reactive ion etch to ensure consistent hydrophobic photoresist: water surface energies. Average parallel contact angle (θ||), average perpendicular contact angle (θ⊥), drop width (W), and drop length (L) at constant volume were measured on nano-patterned surfaces fabricated with interferometric lithography. Both θ|| and θ⊥ contact angles increase as the period (0.3- to 1-μm) increases; the θ|| spreading rate is faster than θ⊥ due to pinning on the grooves resulting in an elongated drop shape. The traditional Wenzel and Cassie-Baxter models of drop contact angles were developed for isotropic random 2D roughness and do not account for the anisotropy induced by the 1D line patterns. The observed angular variations with period are not consistent with either model. Understanding liquid wetting properties and hydrophobicity on 1D silicon surfaces has many applications in lab-on-a-chip, micro/nano-fluidic devices, roll-to-roll nano-imprint fabrication, self-cleaning surfaces, and micro-reactors.

Fabrication of hydrophobic Ti3SiC2 surface with micro-grooved structures by wire electrical discharge machining

The near-superhydrophobic Ti3SiC2 surfaces with regular and controllable micro-grooved structures were fabricated by wire electrical discharge machining (WEDM). The surface topographies and chemical compositions of smooth and micro-grooved Ti3SiC2 surfaces were characterized. The micro removal mechanism of Ti3SiC2 in the process of electrical discharge machining was also analyzed. The wetting mechanism of micro-grooved Ti3SiC2 surface was discussed along with the static contact angle, anisotropic wettability and contact angle evolution versus time. The relationships between parallel and perpendicular contact angles, depth-width ratio of micro-grooved structures and surface roughness of textured surface were investigated. The experimental results show that the parallel contact angle on the textured Ti3SiC2 surface increased by about 164% compared with the one on the smooth surface, and near-superhydrophobic surface with obvious anisotropy was roughly achieved. The experimental parallel contact angles were very close to theoretical contact angles calculated by Cassie-Baxter formula. It is confirmed that the depth-width ratio may be used to predict the parallel contact angle with the average prediction error of 2.4%. The perpendicular contact angles had a good correlation with the depth-width ratio and surface roughness.

Ice Loads Impact on Spillway Culverts Piers in Lithuania

On the basis of literature analysis and field investigations it was found that piers in spillway culverts suffer most from the ice impacts. Floating ice is a significant hazard to structures - jamming between piers or rubble pile development will modify the effective size of the structure and possibly increase the loads. Ice loads are generally described as ice forces or pressures acting over an area of structure. Ice loads are classified as: static loads, dynamic loads, global loads, local loads. Local ice loads from ice-structure interaction are highly irregular and very hard to model exact. The aim of this work - to evaluate ice loads formed in the ponds of Lithuania and their impact on the spillway culverts piers structures. The ice loads were analysed in this work: 1) the force of moving ice fields in contact with single pier; 2) the force of standing ice field, in the impact due wind and water drag forces; 3) the force from ice jam cutting by pier; 4) the force of ice jam in the perpendicular contact with structure front, 5) the force, which is cutting pier of the ice plug.DOI: http://dx.doi.org/10.5755/j01.mech.24.3.21067

Contact angle selection for interfaces in growing domains

AbstractWe study interfaces in an Allen‐Cahn equation, separating two metastable states. Our focus is on a directional quenching scenario, where a parameter renders the system bistable in a half plane and monostable in its complement, with the region of bistability expanding at a fixed speed. We show that the growth mechanism selects a contact angle between the boundary of the region of bistability and the interface separating the two metastable states. Technically, we focus on a perturbative setting in a vicinity of a symmetric situation with perpendicular contact. The main difficulty stems from the lack of Fredholm properties for the linearization in translation invariant norms. We overcome those difficulties establishing Fredholm properties in weighted spaces and farfield‐core decompositions to compensate for negative Fredholm indices.

Architecture for Hard Disk Drives

Magnetic data storage has made rapid progress in terms of areal density over the past few decades. Current products have areal density levels that exceed 1012 bits per square inch, about 1000 times greater than areal densities of the mid-1990s. Five component technologies have become hard-disk-drive industry standards over the past two decades: read heads based on giant magnetoresistance or tunneling magnetoresistance, perpendicular write heads, perpendicular recording media, heaters, and contact detection sensors. At the recording system level, shingled magnetic recording has been implemented by all disk-drive companies, but it has not become a new standard due to the additional penalty in access time (or latency). Here, interlaced magnetic recording and blocked magnetic recording are introduced and compared with conventional and shingled magnetic recording.

Fiberoptic Contact-Force Sensing Electrophysiological Catheters: How Precise Is the Technology?

Contact-force (CF) sensing catheters are increasingly used in electrophysiological procedures due to their efficacy and safety profile. As data about the accuracy of fiberoptic CF technology are scarce, we sought to quantify it using in vitro experiments. A force sensor was built with a flexible membrane to allow exact reference force measurements for each set of experiments. A TactiCath Quartz (TCQ) ablation catheter was brought in contact with the force sensor membrane in order to compare the TCQ force measurements to sensor reference force measurements. Measurements were performed at different tip angles (0°/perpendicular contact, 45°, 90°/parallel contact), with fluid irrigation, different degrees of catheter deflection, and using a sheath. The accuracy of the TCQ force measurements was 0.9 ± 0.9 g (0°), 0.8 ± 0.8 g (45°) and 1.2 ± 1.3 g (90°), 0.8 ± 0.7 g (irrigation), 0.8 ± 0.8 g (deflection), and 0.8 ± 0.9 g (sheath); this was not significantly different among all experimental conditions. The precision was ≤3.8%. CF measurements using a fiberoptic sensing technology show a high level of accuracy and precision, without being significantly influenced by tip angle, fluid irrigation, catheter deflection or use of a sheath.

Electromagnetic Contact-Force Sensing Electrophysiological Catheters: How Accurate is the Technology?

Contact-force (CF) sensing catheters are increasingly used in clinical electrophysiological practice due to their efficacy and safety profile. As data about the accuracy of this technology are scarce, we sought to quantify accuracy based on in vitro experiments. A custom-made force sensor was constructed that allowed exact force reference measurements registered via a flexible membrane. A Smarttouch Surround Flow (ST SF) ablation catheter (Biosense Webster, Diamond Bar, CA, USA) was brought in contact with the membrane of the force sensor in order to compare the ST SF force measurements to force sensor reference measurements. ST SF force sensing technology is based on deflection registration between the distal and proximal catheter tip. The experiment was repeated for n = 10 ST SF catheters, which showed no significant difference in accuracy levels. A series of measurements (n = 1200) was carried out for different angles of force acting to the catheter tip (0°/perpendicular contact, 30°, 60°, 90°/parallel contact). The mean absolute differences between reference and ST SF measurements were 1.7 ± 1.8 g (0°), 1.6 ± 1.2 g (30°), 1.4 ± 1.3 g (60°), and 6.6 ± 5.9 g (90°). Measurement accuracy was significantly higher in non-parallel contact when compared with parallel contact (P < 0.01). Catheter force measurements using the ST SF catheters show a high level of accuracy regarding differences to reference measurements and reproducibility. The reduced accuracy in measurements of 90° acting forces (parallel contact) might be clinically important when creating, for example, linear lesions.