Detachment Force Research Articles

Jasmonic Acid Activates the Fruit-Pedicel Abscission Zone of 'Thompson Seedless' Grapes, Especially with Co-Application of 1-Aminocyclopropane-1-carboxylic Acid.

Two studies were conducted to determine how methyl jasmonate (MeJA), jasmonic acid (JA), and 1-aminocyclopropane-1-carboxylic acid (ACC) affect grape berry abscission in the initial days after treatment. The overarching goal was to determine whether JA, with or without ACC, may hold the potential to sufficiently reduce fruit detachment force (FDF) and increase the proportion of berries with dry stem scars while minimizing preharvest abscission, effects that could be useful in the production of stemless table grapes. On Thompson Seedless grapes, JA was at least as effective as MeJA for stimulating berry abscission based on reduced fruit detachment force (FDF) and yielding detached berries with dry stem scars. Further, since previous studies showed that ACC improved MeJA-induced grape abscission, we tested ACC effects on JA activity. We found that JA rapidly induced preharvest berry abscission, confirming previous results. ACC alone did not induce preharvest berry abscission, but ACC improved the effectiveness of JA on reducing FDF and increasing dry stem scar development. These studies also demonstrated that JA-induced abscission occurs within the first day after treatment. Commercial use of JA plus ACC as an abscission agent requires that FDF sufficiently declines, and the incidence of dry stem scars increases, prior to a significant increase in fruit abscission. However, the rapid progression of fruit abscission may require harvest either within 24 and 48 h after treatment or the use of a passive catch system.

In vitro mucoadhesive properties of hydrophilic polymers: Effects of contact time, disk shape, and molecular weight

AbstractThis study aimed to investigate the effects of various factors, including contact time, disk shape, and polymer molecular weight, on the in vitro mucoadhesive properties of disks prepared using hydrophilic polymers. Mucoadhesive performance was evaluated by measuring the peak detachment force and work of adhesion values using tensile tests. The mucoadhesive force and work of adhesion values increased with increasing contact time between the polymeric disks and mucin gel layer until 60 s. Increased mucoadhesive performances were typically observed when the disks comprised high‐molecular‐weight polymers, which indicates the increase in the entanglement. Increasing the thicknesses of the disks allowed the disks to absorb more water and thereby have more flexible polymeric chains, enhancing the mucoadhesive capacity. The proportional increase in the mucoadhesive force and work values were observed with increasing the surface areas of the disks. In conclusion, this study comprehensively demonstrated the effects of various experimental factors on mucoadhesion.

Climatic indices as markers of table-grapes postharvest quality: A prediction exercise

Climatic conditions have been acknowledged to affect table-grapes production and postharvest quality. The correlation of the monitored environmental conditions such as rainfall and ambient temperature, with postharvest quality properties such as pedicel detachment force, pH, brix, grape volume, for three cultivation years 2015–2017 was analysed. The significance of the climatic variability on the postharvest quality was examined based on a hydrothermic index used in viticultural zoning namely Branas, Bernon, Levadoux (BBL) for two phenological stages the Budbreak-Flowering and Flowering-Veraison. Their analysis revealed correlations of good efficacy between the BudBreak-Flowering BBL and Flowering-Veraison BBL with the postharvest quality, adopting the Box-Cox transformation for variance stabilization and accuracy improvement of Pearson correlation between the analysed variables. The statistical analysis also revealed specific dependencies of the tested quality properties from the climatic indices and management zones that could be implemented in the postharvest management of table-grapes, according to the management zones delineation as these are determined in the context of the precision viticulture.

FTIR microspectroscopic approach to investigate macromolecular distribution in seed coat cross-sections

Cotton seed coat neps (SCNs) are among the least cleanable impurities in textile industry. SCNs can cause problems by persisting into yarn and fabric, reducing yarn strength, increasing yarn ends-down, and even resulting in uneven dye uptake. The study presented herein investigated the effects of the cultivar on the seed coat contamination using a suite of analytical techniques. The cultivar with more SCNs showed a significantly higher average fiber detachment force, and had a significantly larger number of seeds that required a higher force (> 8 N) for fiber detachment compared to the cultivar with less SCNs. The seeds with a strong fiber-seed attachment could lead to breakage of the seed coat during ginning and produce more SCNs. Fourier transform infrared (FTIR) spectroscopy analysis revealed differences in the biochemical composition in the outer epidermal layers of cotton seeds where the fibers are attached. k-mean cluster analysis of FTIR images and their functional group distribution images revealed that the outer layers and the palisade layer of the seed coats had major differences in molecular concentration and distribution that could contribute to cultivar dependence of SCNs. This study could lead to better understanding of the effects of the cultivar on the generation of SCNs.

Alkanes-esters mixed collector enhanced low rank coal flotation: Interfacial interaction between oil drop and coal particle

The interaction between oil collector drop and coal particle is important for low-rank coal (LRC) flotation. This paper investigated such interactions using dodecane (D), ethyl esters (E) and dodecane-esters mixed collector (MC). Measurements of oil drop-coal induction time and detachment force were conducted at a mesoscopic scale. The micro adsorption mechanism of oil collectors was revealed by wetting heats and FTIR measurements. Flotation results showed MC, especially dodecane-ethyl laurate, obtained high yield and low ash clean coal. There was a shorter induction time and higher adhesion strength between LRC particle and MC drop. The wetting heat of MC was greater than the sum of wetting heat of the two single collectors. FTIR analysis indicated that D validly adsorbed to the methyl or aromatic groups, and E bonded with the oxygen-containing groups. The macro flotation results was well interpreted by the interfacial interaction of collector-coal at the mesoscopic and micro scales.

Clinical Functionality of Dispersive OVDs: Improvement of One of the Properties of 3% Hyaluronic Acid and 4% Chondroitin Sulfate Combination

Ophthalmic viscosurgical devices (OVDs) are mainly divided into two general categories: cohesive and dispersive. Dispersive OVDs such as the 3% hyaluronic acid and 4% chondroitin sulfate (HA/CS) combination have excellent adhesion to ocular tissues and protect the corneal endothelium to a greater extent than cohesive OVDs. Herein, we summarize our recent findings regarding one of the properties of the HA/CS combination related to clinical performance. (i) The room temperature stability of OVDs and needle clogging by OVDs remain clinical issues. We demonstrated that adding d-sorbitol to the HA/CS combination preserved its viscosity, which was equivalent after 2 year-storage at room temperature to the viscosity of HA/CS combination stored under refrigeration for 2 years without d-sorbitol. Besides, the HA/CS combination with d-sorbitol could be used repeatedly without cleaning or replacing the needle, suggesting that the addition of d-sorbitol prevents drying and solidification of the OVD on the needle. (ii) Although it can be inferred from numerous studies that the tissue adhesion of OVDs influences their retention by the eye, little is known about the physical properties of OVDs that contribute to intraocular retention. To address this issue, we compared two types of adhesive forces, detachment force and repulsive force, for each OVD. Compared with other dispersive OVDs, the HA/CS combination showed higher values for both adhesive forces. These results suggest that adhesive forces may be used as an index of dispersive OVD retention in the eye.

Dense liquid flotation: Can coarse particle flotation performance be enhanced by controlling fluid density?

• Bubble-load is optimized in bubble-particles aggregates of fine particles compared to coarser ones. • Coarser particles simulate the detachment behavior of finer particles at increased fluid SGs. • Increased critical detachment amplitudes at increased fluid SGs translate to better flotation performance for coarse particles in terms of recovery, rate, and maximum floatable size. • Increasing fluid SG beyond a limit increases the likelihood of detachment in the froth phase. • Particle weight in fluid is the major detachment force, and the effect of cell turbulence on coarse particle flotation performance is largely dependent on it. In this work, we investigate the influence of fluid density on bubble-particle detachment and coarse particle flotation performance. Detachment studies were carried out using an electro-acoustic apparatus in a dense liquid environment using a lithium heteropolytungstate (LST) mixture with subsequent flotation studies carried out in a micro flotation cell at varying fluid densities. Our results indicate that bubble load was inherently limited by particle surface area and weak particle–particle interactions at coarser sizes. Coarser particles tend to follow the detachment behavior of relatively finer particles at increased fluid density. We also found that flotation performance in terms of recovery, rate, and maximum floatable size can be enhanced by controlling fluid density within a stated limit beyond which detachment in the froth phase causes overall performance to drop.

Machine learning-based optimization of the design of composite pillars for dry adhesives

A machine learning-based optimization strategy was used to find optimal designs for adhesive composite pillars with either high adhesion strength or high adhesion tunability. Neural networks were trained with data generated by finite element analysis to predict the adhesion strength of composite pillars with different designs; an average prediction error of less than 1% was achieved. Through a sensitivity study with the trained neural networks, it is found that the geometry of the stiff core above a critical cut off height has no effect on the interfacial stress distribution and the adhesion of the pillar. A randomly initialized constrained optimization algorithm was then applied to the trained neural networks to find the optimal composite pillar design. A composite pillar design with a stiff core that has an enlarged tapered flat end is optimal for realizing robust and high adhesion, since it can achieve high adhesion under different loading and contact conditions. The optimized pillar has a critical normal detachment force that is nearly 11 times that of a homogenous pillar and 1.7 times that of a composite pillar with a simple wide rectangular core under normal loading. A composite pillar with a thin flat stiff core shows the highest effective adhesion difference between being loaded with a normal force and being loaded with a moment.

A 3D Griffith peeling model to unify and generalize single and double peeling theories

It has been shown in recent years that many species in Nature employ hierarchy and contact splitting as a strategy to enhance the adhesive properties of their attachments. Maximizing the adhesive force is however not the only goal. Many animals can achieve a tunable adhesive force, which allows them to both strongly attach to a surface and easily detach when necessary. Here, we study the adhesive properties of 3D dendritic attachments, which are structures that are widely occurring in nature and which allow to achieve these goals. These structures exploit branching to provide high variability in the geometry, and thus tunability, and contact splitting, to increase the total peeling line and thus the adhesion force. By applying the same principles presented by A.A. Griffith 100 years ago, we derive an analytical model for the detachment forces as a function of their defining angles in 3D space, finding as limit cases 2D double peeling and 1D single peeling. We also develop a numerical model, including a nonlinear elastic constitutive law, for the validation of analytical calculations, allowing additionally to simulate the entire detachment phase, and discuss how geometrical variations influence the adhesive properties of the structure. Finally, we also realize a proof of concept experiment to further validate theoretical/numerical results. Overall, we show how this generalized attachment structure can achieve large variations in its adhesive and mechanical properties, exploiting variations of its geometrical parameters, and thus tunability. The in-depth study of similar basic structural units and their combination can in future lead to a better understanding of the mechanical properties of complex architectures found in Nature.

A general solution to the maximum detachment force in thin film peeling

While it is well known that the steady-state detachment force during 90° peeling of an elastic film on a rigid substrate provides a simple and powerful method to determine the interfacial work of adhesion, the situation is less clear for the maximum detachment force associated with the peeling process. Here, we propose a general solution to this maximum detachment force during 90° peeling, which is shown to depend on the interfacial work of adhesion, interfacial strength, bending modulus of the film, as well as an interfacial cohesive law shape factor. Combining this solution with Kendall’s classical model provides a method that allows the interfacial work of adhesion and interfacial strength of a film-substrate system to be simultaneously determined via peeling test.

Adhesion response of filopodia to an AFM lateral detachment force and functional changes after centrifugation of cells grown on nanoporous titanium.

Cells sense and respond to mechanical cues from the surrounding substrate through filopodia. Regulation of cellular biomechanics operates at the nanoscale. Therefore, a better understanding of the relationship between filopodia and nanoscale surface features is highly relevant for the rational design of implant surfaces. The objective of this work was to determine the biomechanical contribution of filopodia and their nanoprotrusions to the adhesive interaction of cells with nanostructured surfaces. We have also analyzed the functional changes of entire cells subjected to an external force. MC3T3-E1 osteogenic cells were cultured on polished (Ti-Control) and nanotextured titanium discs (Ti-Nano). An AFM approach was used to measure the lateral detachment force of filopodia. Filopodia on Ti-Nano exhibited higher resistance to a lateral detachment force, which indicates that they adhere to the surface with more strength. SEM analysis revealed a restructuration of the cell membrane in response to centrifugation, being more evident on Ti-Nano. Fluorescence labeling also highlighted a difference in the mitochondrial footprint, a cellular compartment that provides energy for cellular processes. Together, these results show for the first time that surface topography can change the adhesive interaction of a subcellular structure that is fundamental in sensing physico-chemical surfaces features.

Effect of calcium nitrate treatment on reduction of berry shattering in ‘Cheongsoo’ grape cultivars

This study was conducted to examine the effect of calcium nitrate (CaNO3) on berry shattering in and the fruit characteristics of the ‘Cheongsoo’ grape cultivar. The rate of berry shattering was reduced regardless of CaNO3 concentration when the detachment force of the abscission zone at the stalk-berry junction increased. When 0.8% CaNO3 was treated, the berry shattering rate decreased by approximately 40% compared to the control; this was the lowest value. Furthermore, fruit quality declined and side effects were not observed following the CaNO3 treatment although fruit firmness also increased by 57% compared to the control. These results indicate that treatment with CaNO3 can contribute to stable production of ‘Cheongsoo’ grapes.

Calculating the force-dependent unbinding rate of biological macromolecular bonds from force-ramp optical trapping assays

The non-covalent biological bonds that constitute protein–protein or protein–ligand interactions play crucial roles in many cellular functions, including mitosis, motility, and cell–cell adhesion. The effect of external force (F) on the unbinding rate ({k}_{text{off}}left(Fright)) of macromolecular interactions is a crucial parameter to understanding the mechanisms behind these functions. Optical tweezer-based single-molecule force spectroscopy is frequently used to obtain quantitative force-dependent dissociation data on slip, catch, and ideal bonds. However, analyses of this data using dissociation time or dissociation force histograms often quantitatively compare bonds without fully characterizing their underlying biophysical properties. Additionally, the results of histogram-based analyses can depend on the rate at which force was applied during the experiment and the experiment’s sensitivity. Here, we present an analytically derived cumulative distribution function-like approach to analyzing force-dependent dissociation force spectroscopy data. We demonstrate the benefits and limitations of the technique using stochastic simulations of various bond types. We show that it can be used to obtain the detachment rate and force sensitivity of biological macromolecular bonds from force spectroscopy experiments by explicitly accounting for loading rate and noisy data. We also discuss the implications of our results on using optical tweezers to collect force-dependent dissociation data.

Physio-morphological and Mechanical propertiesof chillies for Mechanical Harvesting

The plants and its produce characteristics are the basis to design a crop specific harvester. The objective of this study was to determine the physical, morphological and mechanical properties of chilli crop and fruits, that can be used in the design of harvester machine. The observations and data were collected by taking measurements at harvesting stage of three chilli cultivars. The fruit bearing behavior of plants was solitary with fruit position erect in Demon F1 and pendent in Araka Meghana and Mahyco Tejaswini. The plant height ranged between 81.76 to 84.87cm depending on cultivars and fruits per plant were170.25 number for Tejaswini, 158.96 and 156.15 number, respectively for Araka Meghana and Demon F1. It was observed that the length and diameter at shoulder of fruits was in the range of 4.97 to 10.44 cm and 0.8 to 1,25 cm, respectively. The moisture content reduced in leaves, stems and fruits as the maturation changed from matured green fruits bearing of plants to semi dry condition. The detachment force of fruits from plants increased as the fruits colour changed from matured green to fully ripened red and there after decreased.

Detachment patterns and impact characteristics of litchi fruit during vibrational harvesting

A high-speed camera was used to study the motions of litchi fruit during vibrational harvesting to investigate fruit detachment patterns. The quasi-static traction and tilting tests, as well as vibrational detachment tests using frequencies of 9, 12 and 15 Hz and amplitudes of 100 and 130 mm, were conducted on ‘Huaizhi’ litchi. A MATLAB program was developed to estimate the motion parameters of the fruit during shaking. The quasi-static tests indicated that the detachment force decreased as the tilting angle increased from 0° to 60° and that most fruit would detach at a certain tilting angle (average value of 62.6°) without traction. The vibrational detachment tests suggested two main reasons for fruit detachment: the stress exceeded the ultimate stress at the fruit–stem junction and fatigue induced by the alternating stress at the junction. Inducing a large tilting angle during shaking was advantageous for creating a high degree of stress at the fruit–stem junction and for achieving a high detachment speed. In general, appropriate increases in the vibration amplitude and frequency decreased the degree of fruit damage by causing fewer impacts. In this study, 12 Hz/130 mm and 15 Hz/100 mm were the optimal parameter combinations to achieve limited litchi fruit damage and high detachment speeds.

Facilitating Large‐Scale Snow Shedding from In‐Field Solar Arrays using Icephobic Surfaces with Low‐Interfacial Toughness

AbstractLarge‐scale accrual of snow and ice on solar arrays in northern latitudes can cause significant power generation losses during winter. Depending on environmental conditions, snow can encompass a wide range in physical characteristics from dry snow (modulus ≈100 kPa and density ≈0.1 g cm−3) to bulk ice (modulus ≈8 GPa and density ≈0.9 g cm−3). This variation in snow morphology has made the development of a passive, broad‐spectrum, snow and ice‐shedding surface challenging. Here, the authors develop one of the first surfaces that simultaneously possesses both low‐interfacial strength (τ˄ice < 50 kPa) and toughness (Γice < 0.5 J m−2) with ice. These surfaces, fabricated via the addition of mobile polymer chains/oils to a thin polymeric coating, require extremely low detachment forces for ice, enabling its passive shedding at virtually any accretion length scale. Preliminary evidence that the new surfaces can shed different forms of snow and ice from field‐deployed solar arrays, over a range of subzero temperatures for several weeks, leading to significant increases in power generation is provided. The optically transparent surfaces are easily scalable and can be widely deployed by the solar industry in areas that see persistent snow. Other applications include automotive windshields, LIDAR covers for autonomous vehicles, and cold climate optical sensors.

The Force Required to Detach a Rotating Particle from a Liquid-Fluid Interface.

The force required to detach a particle from a liquid–fluid interface is a direct measure of the capillary adhesion between the particle and the interface. Analytical expressions for the detachment force are available but are limited to nonrotating particles. In this work, we derive analytical expressions for the force required to detach a rotating spherical particle from a liquid–fluid interface. Our theory predicts that the rotation reduces the detachment force when there is a finite contact angle hysteresis between the particle and the liquid. For example, the force required to detach a particle with an advancing contact angle of 120° and a receding contact angle of 80° (e.g., polydimethylsiloxane particle at a water–air interface) is expected to be 25% lower when the particle rotates while it is detached.

Detachment Force of the Helical Anchor in Mitral Annulus

Helical anchors are used in transcatheter mitral valve repair. The aim of the current study was to investigate effect of helical anchor design, anchored position and biting depth on the detachment force in an in-vitro experiment. Mitral annulus was excised from 36 fresh porcine hearts and mounted in an unaxial test rig. Seven helical anchors were made of stainless steel based on the geometric parameters: outer diameter, wire diameter, and pitch. The helical anchors were screwed in at 3 to 9 o'clock positions of the posterior annulus, namely, P3-9, and pulled out. The pullout force was measured with the maximal pullout force defined as the detachment force. The detachment force within the medial, lateral and central positions were comparable (p ​> ​=0.069). The detachment force at P6 was lowest compared with the medial and lateral positions, and was 5.459 ​± ​0.193 ​N, 5.586 ​± ​0.113 ​N, 8.911 ​± ​0.250 ​N for the anchors in the outer diameters of 3, 4, 5 ​mm, respectively at the pitch of 2 ​mm and the wire diameter of 0.4 ​mm and biting depth of 3 coils. The detachment force increased with the outer and wire diameters, but was not affected by the pitch at the biting depth of 3 coils (p ​≥ ​0.279). The detachment force of the helical anchor is lowest in the central posterior annulus region, and the biting depth in 3 or more coils is recommended. The helical anchor is stronger than the suture.

Development of buccal film formulations and their mucoadhesive performance in biomimetic models

When developing buccal films for oromucosal drug administration, adhesion is essential to ensure sufficient time for permeation of the active ingredient(s) through the oral mucosa and avoid the detachment and subsequent swallowing of the film. In this study, biomimetic materials were evaluated as a replacement for buccal mucosa in mucoadhesion testing and potential adhesives were compared regarding their suitability to increase the adhesion of hypromellose-based oromucosal films. Gelatin gels, as possible biomimetics, failed to mimic the buccal mucosa. Furthermore, esophageal tissue lead to a wider variance of adhesion data despite showing a good correlation with buccal tissue. A synthetic copolymer hydrogel based on hydroxyethylmethacrylate (HEMA) and N-acryloyl glucosamine (AGA) was able to mimic the buccal mucosa in these tests and reduced the variation in the data compared to animal tissue. Adding polyacrylic acid and polyvinylpyrrolidone to the film formulations at a concentration of 5% w/w approximately doubled the maximum detachment force and work of adhesion. Sodium alginate enhanced the adhesive properties moderately but adding chitosan did not significantly increase mucoadhesion. Polyvinylpyrrolidone and polyacrylic acid are rated as strong adhesion enhancers for buccal films and the HEMA/AGA hydrogel is considered as a suitable alternative for animal mucosa in mucoadhesion testing.

On-Demand Manufacturing Capabilities of Mussels Enable Robust Adhesion to Geometrically Complex Surfaces.

Marine mussels have the remarkable ability to adhere to a variety of natural and artificial surfaces under hostile environmental conditions. Although the molecular composition of mussel adhesives has been well studied, a mechanistic understanding of the physical origins of mussels' impressive adhesive strength remains elusive. Here, we investigated the role of substrate geometry in the adhesive performance of mussels. Experimentally, we created substrates with differing surface properties using 3D printing and laser drilling and introduced these to mussels, which in turn adhered to the engineered surfaces via plaque-thread byssal structures. Tensile testing with in situ imaging was conducted to quantify the adhesion strength of the mussel plaques, and the microstructures of the mechanically deformed plaques were characterized using scanning electron microscopy. Our results reveal that the geometry of the surfaces has no significant impact on the detachment force and the strain, whereas the change in adhesion area leads to a different adhesion stress. Ultrastructural analysis confirms the expected presence of an open-cell foamy network coated with the cuticle. The observed detachment dynamics and failure mechanisms do vary depending on the substrate properties, suggesting the presence of substrate-dependent nonuniform stress distributions at the interface. Together, these results show mussels' remarkable ability to adapt to differing physical conditions and demonstrate the importance of the on-demand and in situ manufacturing of the stiff cuticle and relatively compliant adhesive interlayer. The resultant composite structure avoids the formation of prestress during the formation of the adhesive joint, provides conformability to the surface, and helps compensate for local bending interactions to maintain adhesive strength. Our findings suggest forward design strategies to improve adhesive performance on complex surfaces.