Adhesion measured on the attachment pads of Tettigonia viridissima (Orthoptera, insecta)

2000 ◽  
Vol 203 (12) ◽  
pp. 1887-1895 ◽  
Author(s):  
Y. Jiao ◽  
S. Gorb ◽  
M. Scherge
Keyword(s):  
Contact Area ◽  
Silicon Surface ◽  
Compressive Force ◽  
Adhesive Force ◽  
Applied Force ◽  
Adhesive Properties ◽  
Applied Forces ◽  
Series Of Experiments ◽  
Pore Canals ◽  
Adhesive Forces

The tarsi of the cricket Tettigonia viridissima bear flexible attachment pads that are able to deform, replicating the profile of a surface to which they are apposed. This attachment system is supplemented by a secretion produced by epidermal cells and transported onto the surface of the pad through the pore canals of the pad cuticle. This study shows that the secretion alone is necessary, but not sufficient, for adhesion. To account for the full adhesive force, the deformation of the pad and the resulting changes in contact area were considered. In two series of experiments, the adhesive properties of the secretion and the adhesion of the whole pad were measured using a force tester, the sensitivity of which ranged from micronewtons to centinewtons. The adhesive forces of the secretion measured between a smooth sapphire ball with a diameter of 1.47 mm and a flat silicon surface ranged from 0.1 to 0.6 mN. In a control experiment on the silicon surface without secretion, no adhesive force was measured. There was no dependence of the adhesive force on the applied compressive force. When an intact pad was pulled off a flat silicon surface, the adhesive force increased with increasing applied compressive force, but it did not increase further once the applied force exceeded a certain value. The saturated adhesive force, ranging from 0.7 to 1.2 mN, was obtained at applied forces of 0.7-1.5 mN. The hemispherical surface of the pad had a larger contact area and demonstrated greater adhesion under a larger applied force. Adhesion became saturated when a pad was deformed such that contact area was maximal. The tenacity (the adhesive force per unit area) was 1.7-2.2 mN mm(−)(2).

Technique to Measure Adhesive Forces Between Electrospun Nanofibers

2009 ◽  
Vol 1240 ◽  
Author(s):  
Qiang Shi ◽  
Kai-Tak Wan ◽  
Shing-Chung Wong ◽  
Pei Chen ◽  
Todd A. Blackledge
Keyword(s):  
Unit Area ◽  
Fiber Diameter ◽  
Electrospun Nanofibers ◽  
Amorphous Region ◽  
Adhesive Force ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Ultrafine Fibers ◽  
Dry Adhesion ◽  
Adhesive Forces

AbstractDue to the difficulty in handling nanofibers, little is reported and understood on the dry adhesion between electrospun nanofibers. In this study, we develop a technique to measure the dry adhesive forces between electrospun nanofibers. Of critical importance is the ability to mimic naturally occurring dry adhesion such as that between gecko's and spider's foot hairs and untreated surfaces. The adhesion test was performed on two poly(e-caprolactone) electrospun ultrafine fibers using a nanoforce tensile tester. It was found that the adhesive force per unit area increased with decreasing fiber diameter. The degree of crystallinity, order parameters of macromolecules in the amorphous region and crystallite orientation of the spun fibers were determined by the differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The high measured adhesion between single PCL fibers in comparison to other reported values was attributed to crystal orientation due to electrospinning and the increase of adhesive force per unit area with decreasing fiber diameter.

scholarly journals Insights into the rheology of cohesive granular media

2020 ◽  
Vol 117 (15) ◽  
pp. 8366-8373 ◽  
Author(s):  
Sandip Mandal ◽  
Maxime Nicolas ◽  
Olivier Pouliquen
Keyword(s):  
Numerical Simulations ◽  
Granular Materials ◽  
Significant Role ◽  
Granular Media ◽  
Adhesive Force ◽  
Flow Dynamics ◽  
Main Difficulty ◽  
Inclined Plane ◽  
New Approaches ◽  
Adhesive Forces

Characterization and prediction of the “flowability” of powders are of paramount importance in many industries. However, our understanding of the flow of powders like cement or flour is sparse compared to the flow of coarse, granular media like sand. The main difficulty arises because of the presence of adhesive forces between the grains, preventing smooth and continuous flows. Several tests are used in industrial contexts to probe and quantify the “flowability” of powders. However, they remain empirical and would benefit from a detailed study of the physics controlling flow dynamics. Here, we attempt to fill the gap by performing intensive discrete numerical simulations of cohesive grains flowing down an inclined plane. We show that, contrary to what is commonly perceived, the cohesive nature of the flow is not entirely controlled by the interparticle adhesion, but that stiffness and inelasticity of the grains also play a significant role. For the same adhesion, stiffer and less dissipative grains yield a less cohesive flow. This observation is rationalized by introducing the concept of a dynamic, “effective” adhesive force, a single parameter, which combines the effects of adhesion, elasticity, and dissipation. Based on this concept, a rheological description of the flow is proposed for the cohesive grains. Our results elucidate the physics controlling the flow of cohesive granular materials, which may help in designing new approaches to characterize the “flowability” of powders.

Bending of Iron-Gallium (Galfenol) Alloys for Sensor Applications

2005 ◽  
Vol 888 ◽  
Author(s):  
Patrick R. Downey ◽  
Alison B. Flatau
Keyword(s):  
Magnetic Signal ◽  
Sensor Applications ◽  
Bending Loads ◽  
Applied Forces ◽  
Gallium Alloys ◽  
Series Of Experiments ◽  
Magnetostrictive Sensor ◽  
Cantilevered Beams ◽  
Analytic Models ◽  
Iron Gallium

ABSTRACTThis project investigates the magnetomechanical sensing behavior of iron-gallium alloys in response to applied bending loads to identify the relevant design criteria for novel magnetostrictive sensor applications. A series of experiments are conducted on the magnetic induction response of cantilevered beams to dynamic bending loads. Analytic models of the system are formulated from both the constitutive magnetostriction equations and a free energy derivation. Both the experimental and analytical results show a change of as much as 0.3 T of induction can be measured in the samples in response to relatively small applied forces, with the output magnetic signal appearing at twice the frequency of beam vibration.

scholarly journals In the Tactile Discrimination of Compliance, Perceptual Cues in Addition to Contact Area Are Required

2018 ◽  
Vol 62 (1) ◽  
pp. 1535-1539 ◽  
Author(s):  
Chang Xu ◽  
Yuxiang Wang ◽  
Steven C. Hauser ◽  
Gregory J. Gerling
Keyword(s):  
Contact Area ◽  
Active Touch ◽  
Applied Force ◽  
Perceptual Cues ◽  
Tactile Discrimination ◽  
Passive Touch ◽  
Contact Areas ◽  
Effective Dynamic ◽  
Soft Objects ◽  
Finger Pad

In our ability to discriminate compliant, or ‘soft,’ objects, we rely upon information acquired from interactions at the finger pad. We have yet to resolve the most pertinent perceptual cues. However, doing so is vital for building effective, dynamic displays. By introducing psychophysical illusions through spheres of various size and elasticity, we investigate the utility of contact area cues, thought to be key in encoding compliance. For both active and passive touch, we determine finger pad-to-stimulus contact areas, using an ink-based procedure, as well as discrimination thresholds. The findings indicate that in passive touch, participants cannot discriminate certain small compliant versus large stiff spheres, which generate similar contact areas. In active touch, however, participants easily discriminate these spheres, though contact areas remain similar. Supplementary cues based on stimulus rate and/or proprioception seem vital. One cue that does differ for illusion cases is finger displacement given a volitionally applied force.

scholarly journals Investigation of Biomechanical Characteristics of Orthopedic Implants for Tibial Plateau Fractures by Means of Deep Learning and Support Vector Machine Classification

2020 ◽  
Vol 10 (14) ◽  
pp. 4697 ◽  
Author(s):  
Bogdan Niculescu ◽  
Cosmin Ioan Faur ◽  
Tiberiu Tataru ◽  
Bogdan Marian Diaconu ◽  
Mihai Cruceru
Keyword(s):  
Support Vector Machine ◽  
Tibial Plateau ◽  
Orthopedic Implants ◽  
Tibial Plateau Fractures ◽  
Applied Force ◽  
The Other ◽  
Support Vector ◽  
Svm Classifier ◽  
Significant Difference ◽  
Applied Forces

An experimental comparative study of the biomechanical behavior of commonly used orthopedic implants for tibial plateau fractures was carried out. An artificial bone model Synbone1110 was used and a Schatzker V type tibial plateau fracture was created in vitro, then stabilized with three different implant types, classic L plate, Locking Plate System (PLS), and Hybrid External Fixator (HEF). The stiffness of the bone—implant assembly was assessed by means of mechanical testing using an automated testing machine. It was found that the classic L plate type internal implant has a significantly higher value of deformation then the other two implant types. In case of the other implant types, PLS had a better performance than HEF at low and medium values of the applied force. At high values of the applied forces, the difference between deformation values of the two types became gradually smaller. An Artificial Neural Network model was developed to predict the implant deformation as a function of the applied force and implant device type. To establish if a clear-cut distinction exists between mechanical performance of PLS and HEF, a Support Vector Machine classifier was employed. At high values of the applied force, the Support Vector Machine (SVM) classifier predicts that no statistically significant difference exists between the performance of PLS and HEF.

scholarly journals Mitigating the charge trapping effects of D-sorbitol/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) polymer blend contacts to crystalline silicon

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Daniel Cohen ◽  
Esha Thakur ◽  
Michael G. Walter
Keyword(s):  
Polymer Blend ◽  
Silicon Surface ◽  
Crystalline Silicon ◽  
Conductive Polymer ◽  
Surface Oxidation ◽  
Charge Trapping ◽  
Device Performance ◽  
Trap States ◽  
Adhesive Properties ◽  
Surface Trap

Abstract Solution-processable conductive polymers are advantageous materials for making inexpensive, electrical junctions to crystalline semiconductors. We have investigated methods to improve the device performance of hybrid solar cells made from n-type silicon and a conductive polymer glue based on a blend of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and D-sorbitol. The PEDOT:PSS blend behaves like a high work function metal creating a Schottky-type junction. The addition of D-sorbitol increases PEDOT:PSS conductivity and provides adhesive properties, allowing the top contact of the solar cell to be laminated onto the silicon substrate. Unfortunately, the addition of the D-sorbitol to the PEDOT:PSS significantly alters the shape of the measured current-voltage performance curve of a crystalline silicon (n-Si)/PEDOT:PSS junction. Under illumination, this results in a decline in the fill factor (FF) and a drop in photocurrent density (J sc) compared to PEDOT:PSS-only devices. We have discovered that the decline in device performance is likely due to surface trap states caused by D-sorbitol/silicon interaction and/or silicon oxidation. X-ray photoelectron spectroscopic (XPS) analysis shows that surface oxidation quickens, and possible silicon surface functionalization with D-sorbitol occurs while processing the D-sorbitol/PEDOT:PSS contact on H-terminated surfaces. To overcome these interface issues, the silicon surface was chemically modified using surface methylation, making it insensitive to D-sorbitol/silicon interactions and surface oxidation during the processing of the PEDOT:PSS polymer blend contact. This also enabled the crystalline silicon (n-Si)/s-PEDOT:PSS device performance to be maintained for longer periods. Using a silicon surface methylation strategy, good device performance could be achieved without changing the adhesive properties of D-sorbitol/PEDOT:PSS polymer blend.

scholarly journals Fifth fundamental force and unification of fundamental forces

2021 ◽  
Author(s):  
Raghvendra Singh
Keyword(s):  
Water Drop ◽  
Surface Force ◽  
Adhesive Force ◽  
The Other ◽  
Unified Theory ◽  
Fifth Force ◽  
Functional Forms ◽  
Fundamental Forces ◽  
The Universe ◽  
Adhesive Forces

Abstract There are four known fundamental forces of nature and there is a need to combine them into a unified theory. Progress has been made toward this goal but gravity remains an issue. However, the four forces are body forces that act on points. They together do not make the universe a closed system. Here, I identify a surface force, which acts outward normal to the surface of the universe. Further, using water drop hanging in a vacuum as a model, I provide a formula to find the magnitude of this force. The fifth force is generated by the surface tension, a property of dark energy. On the other hand, matter particles interact with each other through a cohesive force and with dark matter through an adhesive force. I give a range of the functional forms of all cohesive and adhesive forces and present an equation that unifies all the forces of nature.

Design and Testing of a Wall-Climbing Robot With Under-Actuated Force Adjusting Mechanism

2019 ◽  
Author(s):  
Xuan Wu ◽  
Hong Liu ◽  
Xiaojie Wang
Keyword(s):  
Adhesive Force ◽  
Experimental Results ◽  
Climbing Robot ◽  
Adhesive Properties ◽  
Dry Adhesive ◽  
Link Functions ◽  
Design And Testing

Abstract The paper introduces the design and testing of a tank-like modular wall-climbing robot (WCR). Firstly, a bioinspired dry adhesive patterned with papilla-like array is fabricated, and its quasi-static adhesive properties is tested and evaluated. Based on the material’s properties, a single tank-like module using timing adhesive belts is optimally designed for maximum adhesive force. An under-actuated four-bar compliant linkage is utilized to connect the two modules of the WCR. The lengths of the linkage are optimized in keeping both of the modules having constant preloading forces on surfaces with different inclinations. Experimental results show that the compliant link functions like the digital joint of the gecko that is able to maintain enough preloading force for each module on the surfaces of variable inclinations, making the robot adapted to surface transitioning easily.

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