Easy Detachment Research Articles

Using Sparkleberry as a Genetic Source for Machine Harvest Traits for Southern Highbush Blueberry

Because of financial and labor concerns, growers are interested in using machine harvesting for fruit destined to be fresh marketed. Machine harvest of highbush blueberry (Vaccinium corymbosum) has typically been used to obtain large volumes of fruit destined for processing. Bush architecture, easy detachment of mature berries compared with immature berries, loose fruit clusters, small stem scar, firm fruit, and a concentrated ripening period are breeding goals to develop cultivars amenable to machine harvest. In the University of Florida (UF) southern highbush blueberry [SHB (Vaccinium corymbosum hybrids)] breeding program, sparkleberry (Vaccinium arboreum) has been used in wide crosses in an attempt to introgress traits that may be valuable for machine harvesting, namely upright growth habit with a narrow crown and long flower and fruit pedicels creating loose fruit clusters. Two eras of sparkleberry hybridization experiments have occurred since the early 1980s. The first era used darrow’s evergreen blueberry (Vaccinium darrowii) as a bridge between sparkleberry and tetraploid SHB, with the recently released cultivar FL 01-173 (sold under the trademarked name Meadowlark) as an example of the end product. The second era has used chromosome doubling to develop polyploid sparkleberry selections that were directly crossed with tetraploid SHB. After 1 year of evaluation, a SHB × (SHB × sparkleberry) population developed for linkage and quantitative trait locus mapping showed abundant variation for length:width ratio of the plant, but similarity to the highbush phenotype for peduncle and pedicel length of the fruit. These first evaluations indicate evidence of introgression and provide an initial step toward improved cultivars for mechanical harvesting.

Role of surface wettability and roughness in emulsion separation

Droplet interaction with a surface placed in an immiscible liquid surrounding is very important for liquid–liquid separation. This study investigates the influence of filter surface energy (14–43mN/m), micro- and nanoscale surface roughness on wetting, mobility and coalescence of isooctane droplets (5–10μl) in immiscible water surrounding and explains their role in emulsion separation performance of nanoparticle coated filters. In water, coalescence among the oil droplets primarily takes place at filter surface. Despite different interfacial energies in air and water surrounding, the influence of substrate roughness on droplet mobility is same in both the surroundings. For effective separation of oil-in-water emulsion with a surface filter, it should be super hydrophilic, oriented vertically and have pore size smaller than the dispersed droplet size. In addition, the influent side of a surface filter should possess sufficient micro- and nanoscale surface roughness to provide high mobility, coalescence of the oil droplets and thereafter their easy detachment. For effective separation of oil from water a coalescing filter should be hydrophobic–oleophilic, oriented vertically with rough fibers surface to offer strong adhesion with the oil droplets and thereby high coalescence efficiency.

Instantly switchable adhesion of bridged fibrillar adhesive via gecko-inspired detachment mechanism and its application to a transportation system

Inspired by the exceptional climbing ability of gecko lizards, artificial fibrillar adhesives have been extensively studied over the last decade both experimentally and theoretically. Therefore, a new leap towards practical uses beyond the academic horizon is timely and highly anticipated. To this end, we present a fibrillar adhesive in the form of bridged micropillars and its application to a transportation system with the detachment mechanism inspired by the climbing behaviour of gecko lizards. The adhesive shows strong normal attachment (~30 N cm(-2)) as well as easy and fast detachment within 0.5 s without involving complex dynamic mechanisms or specific stimulus-responsive materials. The fabrication of the bridged micropillars consists of replica moulding of polydimethylsiloxane (PDMS) micropillars, transfer of the PDMS precursor to the heads of the micropillars, and inverse placement on an inert Teflon-coated surface. Owing to the spontaneous interconnections of low viscosity PDMS precursor, bridged micropillars with a uniform capping nanomembrane (~800 nm thickness) are formed over a large area. Interestingly, macroscopic adhesion in the normal direction can be immediately switched between on and off states by changing the two detachment modes of pulling and peeling, respectively. To prove the potential of the fibrillar adhesive for practical use, an automated transportation system is demonstrated for lifting and releasing a mass of stacked glass slides over 1000 cycles of attachment and detachment.

A high poly(ethylene glycol) density on graphene nanomaterials reduces the detachment of lipid–poly(ethylene glycol) and macrophage uptake

Amphiphilic lipid–poly(ethylene glycol) (LPEG) is widely used for the noncovalent functionalization of graphene nanomaterials (GNMs) to improve their dispersion in aqueous solutions for biomedical applications. However, not much is known about the detachment of LPEGs from GNMs and macrophage uptake of dispersed GNMs in relation to the alkyl chain coverage, the PEG coverage, and the linker group in LPEGs. In this study we examined these relationships using single walled carbon nanohorns (SWCNHs). The high coverage of PEG rather than that of alkyl chains was dominant in suppressing the detachment of LPEGs from SWCNHs in protein-containing physiological solution. Correspondingly, the quantity of LPEG-covered SWCNHs (LPEG-SWCNHs) taken up by macrophages decreased at a high PEG coverage. Our study also demonstrated an effect of the ionic group in LPEG on SWCNH uptake into macrophages. A phosphate anionic group in the LPEG induced lower alkyl chain coverage and easy detachment of the LPEG, however, the negative surface charge of LPEG-SWCNHs reduced the uptake of SWCNHs by macrophages.

An accordion model integrating self-cleaning, strong attachment and easy detachment functionalities of gecko adhesion

Recent experiments have shown that gecko adhesion exhibits multifunctionalities including self-cleaning, strong attachment and easy detachment. Currently, there exists no theoretical framework in contact mechanics that is capable of integrating all these features in one unified model. Here we propose an accordion model of adhesion that accomplishes this integration with an adhesive pad consisting of a compliant backbone covered by a foldable hard skin containing hidden adhesives which are initially folded into the structure to avoid adhesion in the stress-free state. At the default, stress-free state, the pad is non-adhesive and self-cleaning. Under a tensile prestress large enough to expose the hidden adhesives, the pad becomes highly stiffened and strongly adhesive. We investigate the adhesion behavior of such a structure and show that strong attachment can be established spontaneously when the pad is dragged on an external surface at a low angle, with prestress trapped in the attached portion of the pad. We then investigate the orientation-dependent peel-off force of an attached accordion pad and show that it can be spontaneously detached above a critical pulling angle, leading to strongly reversible adhesion.

Rational Design and Nanofabrication of Gecko‐Inspired Fibrillar Adhesives

Gecko feet integrate many intriguing functions such as strong adhesion, easy detachment, and self-cleaning. Mimicking gecko toe pad structure leads to the development of new types of fibrillar adhesives useful for various applications. In this Concept article, in addition to the design of adhesive mimics by replicating gecko geometric features, we show a new trend of rational design by adding other physical, chemical, and biological principles on to the geometric merits, for enhancing robustness, responsive control, and durability. Current challenges and future directions are highlighted in the design and nanofabrication of biomimetic fibrillar adhesives.

Quantifying Information Transfer Through a Head-Attached Vibrotactile Display: Principles for Design and Control

Vibrotactile displays can extend the perception capabilities of visually impaired persons. Placing such devices on the head promises easy attachment and detachment without reducing other interaction abilities. However, the effectiveness of head-attached vibrotactile displays has never been thoroughly tested. This paper presents the results obtained from experiments with 22subjects equipped with a display containing 12 coin-type motors equally spaced in a horizontal plane around the upper head region. Our display allowed single- as well as multimotor activation with up to six simultaneously active motors. We identified the minimum and comfort strength of vibrotactile stimulation, and measured the precision in perceiving the accurate number of active motors as well as the precision in localizing the stimuli on the head. While subjects identified the correct number of active motors in 94% of the cases when presented with only one active motor, this precision dropped to 40% for two and down to 5% for five simultaneously active motors. This strongly suggests to avoid multipoint stimulation even though the precision of localizing a position of a stimulus on the head is barely affected by the number of simultaneously active motors. Localization precision, however, varied significantly with the region of the head suggesting that the most front and back regions of the head should be avoided if high precision is required.

Active Connection Mechanism for Soft Modular Robots

To date, most modular robotic systems lack flexibility when increasing the number of modules due to their hard building blocks and rigid connection mechanisms. In order to improve adaptation to environmental changes, softness at the module level might be beneficial. However, coping with softness requires a fundamental rethinking of the way modules are built. A major challenge is to develop a connection mechanism that does not limit the softness of the modules, does not require precise alignment and allows for easy detachment. In this paper, we propose a soft active connection mechanism based on electroadhesion. The mechanism uses electrostatic forces to connect modules. The method is easy to implement and can be integrated in a wide range of soft module types. Based on our experimental results, we conclude that the mechanism is suitable as a connection principle for lightweight modules when efficiency over a wide range of softness, tolerance to alignment and easy detachment are desired. The main contributions of this paper are (i) the qualitative comparison of different connector principles for soft modular robots, (ii) the integration of electroadhesion, featuring a novel electrode pattern design, into soft modules and (iii) the demonstration and characterization of the performance of functional soft module mockups including the connection mechanism.

Segregation Growth of Graphene on Cu–Ni Alloy for Precise Layer Control

A facile way to segregate wafer-size graphene with controllable layer number using Cu–Ni binary alloy under vacuum annealing condition is presented here. Increasing atomic percentage of Ni in Cu–Ni alloy was found to segregate thicker uniform graphene. To date, over 95% monolayer and 91% bilayer graphene films have been prepared by only changing atomic percentage of Ni in Cu–Ni alloy, respectively. The synergetic combination of the distinct carbon solubilities of Cu and Ni and the well-known segregation phenomenon is believed to be responsible for the formation of high-quality uniform few layer graphene. Together with the easy detachment from growth substrates, we believe this facile segregation technique will offer a great driving force for graphene research.

Optimal Design of High-Aspect-Ratio Micro/Nano Hierarchical Structures Mimicking Gecko Foot-Hairs

Geckos have extraordinary climbing ability. The multi-scale hierarchical structure of the gecko foot-hairs, especially the high-aspect-ratio structure of its micro-scale seta and nano-scale spatulae is the critical factor of the gecko’s ability to adopt and stick to any different surface with powerful adhesion force. In this paper, a series of models such as robust adhesion, easy detachment, rough surface adaption, anti-bunching and anti-fracture, have been proposed by simulating gecko’s attachment. Based on these models, we have launched a bottomup methodology for designing the high-aspect-ratio hierarchical structure mimicking gecko’s dry adhesive pad. A skillful procedure is also developed here to find out optimum parameters by multi-object optimization, including the hierarchical structural dimensions, the density and pattern of the fibers, and the geometric parameters of the single fiber. The outcome illustrates that the optimal designed parameters of the structure are analogous to those of geckos observed. Especially, the simulated adhesion force of the structure is consistent with the measured value of a single seta, which proves that the optimized structure also has powerful adhesive ability like geckos.

Universal Segregation Growth Approach to Wafer-Size Graphene from Non-Noble Metals

Graphene has been attracting wide interests owing to its excellent electronic, thermal, and mechanical performances. Despite the availability of several production techniques, it is still a great challenge to achieve wafer-size graphene with acceptable uniformity and low cost, which would determine the future of graphene electronics. Here we report a universal segregation growth technique for batch production of high-quality wafer-scale graphene from non-noble metal films. Without any extraneous carbon sources, 4 in. graphene wafers have been obtained from Ni, Co, Cu-Ni alloy, and so forth via thermal annealing with over 82% being 1-3 layers and excellent reproducibility. We demonstrate the first example of monolayer and bilayer graphene wafers using Cu-Ni alloy by combining the distinct segregation behaviors of Cu and Ni. Together with the easy detachment from growth substrates, we believe this facile segregation technique will offer a great driving force for graphene research.

Electricity Generation from MFCs Using Differently Grown Anode-Attached Bacteria

To understand the effects of acclimation schemes on the formation of anode biofilms, different electrical performances are characterized in this study, with the roles of suspended and attached bacteria in single-chamber microbial fuel cells (MFCs). The results show that the generation of current in single-chamber MFCs is significantly affected by the development of a biofilm matrix on the anode surface containing abundant immobilized microorganisms. The long-term operation with suspended microorganisms was demonstrated to form a dense biofilm matrix that was able to reduce the activation loss in MFCs. Also, a Pt-coated anode was not favorable for the initial or long-term bacterial attachment due to its high hydrophobicity (contact angle = 124˚), which promotes easy detachment of the biofilm from the anode surface. Maximum power (655.0mW/m2) was obtained at a current density of 3,358.8mA/m2 in the MFCs with longer acclimation periods. It was found that a dense biofilm was able to enhance the charge transfer rates due to the complex development of a biofilm matrix anchoring the electrochemically active microorganisms together on the anode surface. Among the major components of the extracellular polymeric substance, carbohydrates (85.7mg/m2 (anode)) and proteins (81.0mg/m2 (anode)) in the dense anode biofilm accounted for 17 and 19%, respectively, which are greater than those in the sparse anode biofilm.

Adhesion hysteresis of Janus nanopillars fabricated by nanomolding and oblique metal deposition

Summary We present a simple method to fabricate Janus-faced nanopillars showing the direction-sensitive behavior as a dry adhesive. Polymeric nanopillars were first molded from an etched SiO 2 substrate containing high aspect ratio nanoholes, followed by the oblique metal deposition on polymer nanopillars such that metal layers in different thicknesses were selectively deposited only on one side of the nanopillars. We found that the Janus nanopillars show the asymmetric adhesion behavior: it exhibits the strong shear attachment when pulled from a polymer contact (∼20 N/cm 2 ) compared with the relatively weak adhesion when pulled from a metal layer in contact with a glass substrate (∼10 N/cm 2 ). The difference in the shear adhesion strength is believed to originate from different interfacial adhesions between different sides of the Janus nanopillars and a target substrate. In addition, the Janus nanopillars could be further allowed to bend by thermal annealing or E-beam irradiation. The bending mechanism for nanopillars bending toward the metal layer by thermal annealing can be explained by the mismatch in thermal expansion coefficients between metal and polymer, followed by the plastic deformation of polymeric pillars. What is strikingly interesting is the fact that these bent Janus nanopillars show even greater adhesion hysteresis: the strong shear attachment when pulled from the bent direction (∼31 N/cm 2 ) in contrast to the easy detachment from the opposite direction (∼4.1 N/cm 2 ) just like gecko-like adhesives. We also demonstrate that this type of relatively simple bending process to produce Janus-faced nanopillars has a distinct advantage for large-area fabrication.

SU-FF-T-55: A Novel Applicator System for HDR Treatment of Endometrial and Cervical Cancer

Purpose: A new HDR applicator system has been designed to treat gynecological cancers with following specific goals in mind: 1) ability to do volumetric image based patient specific dosimetry, 2) ability to significantly spare the surrounding critical structures, 3) Performing volumetric dosimetry based on delineated target volume and moving away from Manchester point calculation, and 4) provide patient comfort during the implant. It is expected that this system will provide all the functionality of a Fletcher-Suit-Delclos (FSD) device and has more versatility in treatment of these cancers. Method and Materials: A disposable applicator manufactured* from plastic material with inflatable partitioned sections to displace rectum and bladder away from the radiation source has been designed. Monte Carlo simulations were performed to compare dosimetry with conventional Manchester system and show superiority of this device in delivering dose to the target volume while sparing rectum and bladder. Comparable optimized plans with conventional FSD system were made using BrachyVision system. Results: Preliminary trials of this applicator used on cadavers revealed superiority in inserting the system in cervical canal through stent, filling the vaginal cavity with liquid contrast for proper CT/MRI imaging. The unaccounted attenuation from the Stainless Steel tubing in FSD applicator is no longer an issue when this applicator is implemented. This new applicator manufactured from all disposable plastic materials, is CT & MR friendly, allows 3-D treatment planning executable to accurately deliver dose to the target volume as prescribed, allows sparing the normal tissue structure at any desirable level. Our dosimetric studies indicate superior volumetric dose coverage to PTV and easy detachment from the conventional Manchester system. Conclusions: The new applicator once applied will overcome most of the disadvantages from the conventional FSD device and offers numerous superior clinical advantages for patients with gynecological cancer. *Project supported by Varian Medical-system

A Mechanical Model for the Adhesion of Spiders to Nominally Flat Surfaces

In dry attachment systems of spiders and geckos, van der Waals forces mediate attraction between substrate and animal tarsus. In particular, the scopula of Evarcha arcuata spiders allows for reversible attachment and easy detachment to a broad range of surfaces. Hence, reproducing the scopula's roughness compatibility while maintaining anti-bunching features and dirt particle repellence behavior is a central task for a biomimetic transfer to an engineered model. In the present work we model the scopula of E. arcuata from a mechano-elastic point of view analyzing the influence of its hierarchical structure on the attachment behavior. By considering biological data of the gecko and spider, and the simulation results, the adhesive capabilities of the two animals are compared and important confirmations and new directives in order to reproduce the overall structure are found. Moreover, a possible suggestion of how the spider detaches in an easy and fast manner is proposed and supported by the results.

A nontransferring dry adhesive with hierarchical polymer nanohairs

We present a simple yet robust method for fabricating angled, hierarchically patterned high-aspect-ratio polymer nanohairs to generate directionally sensitive dry adhesives. The slanted polymeric nanostructures were molded from an etched polySi substrate containing slanted nanoholes. An angled etching technique was developed to fabricate slanted nanoholes with flat tips by inserting an etch-stop layer of silicon dioxide. This unique etching method was equipped with a Faraday cage system to control the ion-incident angles in the conventional plasma etching system. The polymeric nanohairs were fabricated with tailored leaning angles, sizes, tip shapes, and hierarchical structures. As a result of controlled leaning angle and bulged flat top of the nanohairs, the replicated, slanted nanohairs showed excellent directional adhesion, exhibiting strong shear attachment (approximately 26 N/cm(2) in maximum) in the angled direction and easy detachment (approximately 2.2 N/cm(2)) in the opposite direction, with a hysteresis value of approximately 10. In addition to single scale nanohairs, monolithic, micro-nanoscale combined hierarchical hairs were also fabricated by using a 2-step UV-assisted molding technique. These hierarchical nanoscale patterns maintained their adhesive force even on a rough surface (roughness <20 microm) because of an increase in the contact area by the enhanced height of hierarchy, whereas simple nanohairs lost their adhesion strength. To demonstrate the potential applications of the adhesive patch, the dry adhesive was used to transport a large-area glass (47.5 x 37.5 cm(2), second-generation TFT-LCD glass), which could replace the current electrostatic transport/holding system with further optimization.

Gasket with easy component attachment and detachment, and use in refrigerator

Gasket with easy component attachment and detachment, and use in refrigerator

Spiderman gloves

Theoretical van der Waals gloves could generate an adhesion force comparable to the body weight of ∼500 men. Even if such a strength remains practically unrealistic (and undesired, in order to achieve an easy detachment), due to the presence of contact defects, e.g. roughness and dust particles, its huge value suggests the feasibility of Spiderman gloves. The scaling-up procedure, from a spider to a man, is expected to decrease the safety factor (body weight over adhesion force) and adhesion strength, that however could remain sufficient for supporting a man. Scientists are developing new biomimetic materials, e.g. gecko-inspired. Here we complementary face the problem of the structure rather than of the material, designing and preliminary fabricating a first prototype of Spiderman gloves, capable of supporting ∼10 kilograms each on vertical walls. New Adhesive Optimization Laws are derived and applied for increasing the capability of the scaling-up.

Hierarchical modelling of attachment and detachment mechanisms of gecko toe adhesion

The mechanics of reversible adhesion of the gecko is investigated in terms of the attachment and detachment mechanisms of the hierarchical microstructures on its toe. At the bottom of the hierarchy, we show that a spatula pad of tiny thickness can be well absorbed onto a substrate with a large surface area and a highly constrained decohesion process zone, both of which are beneficial for robust attachment. With different peeling angles, the peeling strength of a spatula pad for attachment can be 10 times larger than that for detachment. At the intermediate level of hierarchy, we show that a seta can achieve a stress level similar to that in the spatula pad by uniformly distributing adhesion forces; as a consequence, the 10 times difference in the peel-off force of a single spatula pad for attachment and detachment is magnified up to a 100 times difference in adhesion energy at the level of seta. At the top of the hierarchy, the attachment process of a gecko toe is modelled as a pad under displacement-controlled pulling, leading to an adhesive force much larger than the gecko's body weight, while the associated detachment process is modelled as a pad under peeling, resulting in a negligible peel-off force. The present work reveals, in a more systematic way than previous studies in the literature, that the hierarchical microstructures on the gecko's toe can indeed provide the gecko with robust adhesion for attachment and reversible adhesion for easy detachment at the same time.

Three-level hierarchal modeling of gecko toe adhesion

ABSTRACTThe underlying mechanisms of gecko adhesion have been investigated through modeling of the three-level hierarchical microstructures under gecko's toe [1]. At the bottom of hierarchy, we show that the peeling strength of a spatula pad for attachment can be 10 times larger than that for detachment. At the intermediate level of hierarchy, we show that the 10 times difference in the peeling strength of a spatula pad for attachment and detachment leads to a 100 times difference in adhesion energy at the level of seta. At the top of hierarchy, the attachment of a gecko toe is modeled as a pad under displacement controlled pulling, which yields an adhesive strength more than sufficient for gecko's body weight; On the other hand, the detachment is modeled as a pad under peeling, giving rise to a negligible peel-off force. The present study reveals that the hierarchical microstructures play critical roles in providing gecko with robust attachment and easy detachment.