scholarly journals Sticking to rough surfaces using functionally graded bio-inspired microfibres

2017 ◽  
Vol 4 (6) ◽  
pp. 161105 ◽  
Author(s):  
Serdar Gorumlu ◽  
Burak Aksak
Keyword(s):  
Rough Surfaces ◽  
Functionally Graded ◽  
Smooth Surfaces ◽  
Threefold Increase ◽  
Adhesion Measurement ◽  
Natural Analogues ◽  
Distance Data ◽  
Fibrillar Adhesives ◽  
System Average ◽  
Adhesive Performance

Synthetic fibrillar adhesives inspired by nature, most commonly by the gecko lizard, have been shown to strongly and repeatedly attach to smooth surfaces. These adhesives, mostly of monolithic construction, perform on par with their natural analogues on smooth surfaces but exhibit far inferior adhesive performance on rough surfaces. In this paper, we report on the adhesive performance of functionally graded microfibrillar adhesives based on a microfibre with a divergent end and a thin soft distal layer on rough surfaces. Monolithic and functionally graded fibre arrays were fabricated from polyurethanes and their adhesive performance on surfaces of varying roughness were quantified from force–distance data obtained using a custom adhesion measurement system. Average pull-off stress declined significantly with increasing roughness for the monolithic fibre array, dropping from 77 kPa on the smoothest (54 nm RMS roughness) to 19 kPa on the roughest (408 nm RMS roughness) testing surface. In comparison, pull-off stresses of 81 kPa and 63 kPa were obtained on the same respective smooth and rough surfaces with a functionally graded fibre array, which represents a more than threefold increase in adhesion to the roughest adhering surface. These results show that functionally graded fibrillar adhesives perform similar on all the testing surfaces unlike monolithic arrays and show potential as repeatable and reusable rough surface adhesives.

scholarly journals Normal contact and friction of rubber with model randomly rough surfaces

Soft Matter ◽  
2015 ◽  
Vol 11 (5) ◽  
pp. 871-881 ◽  
Author(s):  
S. Yashima ◽  
V. Romero ◽  
E. Wandersman ◽  
C. Frétigny ◽  
M. K. Chaudhury ◽  
...  
Keyword(s):  
Rough Surfaces ◽  
Statistical Distribution ◽  
Smooth Surfaces ◽  
Normal Contact ◽  
Randomly Rough Surfaces ◽  
Friction Measurements

We report on normal contact and friction measurements of model multicontact interfaces formed between smooth surfaces and substrates textured with a statistical distribution of spherical micro-asperities.

Measurements of the Boundary Layer Development along a Turbine Blade with Rough Surfaces

1980 ◽  
Vol 102 (4) ◽  
pp. 978-983 ◽  
Author(s):  
K. Bammert ◽  
H. Sandstede
Keyword(s):  
Boundary Layer ◽  
Rough Surfaces ◽  
Chord Length ◽  
Smooth Surfaces ◽  
Turbine Cascade ◽  
Boundary Layer Development ◽  
Turbine Cascades ◽  
Layer Development ◽  
Good Agreement

During the operation of turbines the surfaces of the blades are roughened by corrosion, erosion and deposits. The generated roughness is usually greater than that produced by manufacture. The quality of the blade surfaces determines the losses of energy conversion in turbine cascades to a great extent. The loss coefficient can be found theoretically by a boundary layer calculation. For rough surfaces there are no boundary layer measurements along the profiles of a turbine cascade. Therefore in a cascade wind tunnel measurements of the boundary layer development were carried out. The chord length of the blades was 175 mm. The cascade represented a section through the stator blades of a 50 percent reaction gas turbine. For smooth surfaces and three different roughnesses up to 3.3 · 10−3 (equivalent sand roughness related to chord length) the boundary layers were measured. The momentum thickness is up to three times as great as that on smooth surfaces. Especially in regions with decelerated flow the effects of roughness are high. A rough surface causes a rise of the friction factor and a shift of the transition of laminar to turbulent flow. The results of the measurements are shown. Correction factors are worked out to get good agreement between measurement and calculation according to the Truckenbrodt theory.

Novel Noncontact Thickness Metrology for Partially Transparent and Nontransparent Wafers for Backend Semiconductor Manufacturing

2004 ◽  
Vol 829 ◽  
Author(s):  
Wojciech J. Walecki ◽  
Vitali Souchkov ◽  
Kevin Lai ◽  
Phuc Van ◽  
Manuel Santos ◽  
...  
Keyword(s):  
Semiconductor Manufacturing ◽  
Rough Surfaces ◽  
Optical Interferometry ◽  
Smooth Surfaces ◽  
Low Coherence ◽  
Low Coherence Interferometry ◽  
Single Probe ◽  
Thin Semiconductor ◽  
Compound Materials

ABSTRACTSingle probe infrared low coherence optical interferometry has been proven to be an effective tool for characterization of thin and ultra-thin semiconductor Si and compound materials wafers. Its application was however limited to wafers transparent at probing wavelength, and having relatively smooth surfaces. Purpose of this paper is to present an extension of low coherence interferometry to characterization of non-transparent wafers, and wafers with rough surfaces.

Arachidonic Acid and Prostaglandin E2 Influence Human Osteoblast (MG63) Response to Titanium Surface Roughness

2008 ◽  
Vol 34 (6) ◽  
pp. 303-312 ◽  
Author(s):  
David D. Dean ◽  
Casey M. Campbell ◽  
Scott F. Gruwell ◽  
John W. M. Tindall ◽  
Hui-Hsiu Chuang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Arachidonic Acid ◽  
Thymidine Incorporation ◽  
Specific Activity ◽  
Rough Surfaces ◽  
Cell Number ◽  
Smooth Surfaces ◽  
Implant Surface ◽  
Implant Placement ◽  
Effect Of Treatment

Abstract Prior studies have shown that implant surface roughness affects osteoblast proliferation, differentiation, matrix synthesis, and local factor production. Further, cell response is modulated by systemic factors, such as 1,25(OH)2D3 and estrogen as well as mechanical forces. Based on the fact that peri-implant bone healing occurs in a site containing elevated amounts of prostaglandin E2 (PGE2), the hypothesis of the current study is that PGE2 and arachidonic acid (AA), the substrate used by cyclooxygenase to form PGE2, influence osteoblast response to implant surface roughness. To test this hypothesis, 4 different types of commercially pure titanium (cpTi) disks with surfaces of varying roughness (smooth Ti, Ra 0.30 μm; smooth and acid etched Ti [SAE Ti], Ra 0.40 μm; rough Ti, Ra 4.3 μm; rough and acid etched Ti [RAE Ti], Ra 4.15μm) were prepared. MG63 osteoblasts were seeded onto the surfaces, cultured to confluence, and then treated for the last 24 hours of culture with AA (0, 0.1, 1, and 10 nM), PGE2 (0, 1, 10, 25, and 100 nM), or the general cyclooxygenase inhibitor indomethacin (0 or 100 nM). At harvest, the effect of treatment on cell proliferation was assessed by measuring cell number and [3H]-thymidine incorporation, and the effect on cell differentiation was determined by measuring alkaline phosphatase (ALP) specific activity. The effect of AA and PGE2 on cell number was somewhat variable but showed a general decrease on plastic and smooth surfaces and an increase on rough surfaces. In contrast, [3H]-thymidine incorporation was uniformly decreased with treatment on all surfaces. ALP demonstrated the most prominent effect of treatment. On smooth surfaces, AA and PGE2 dose-dependently increased ALP, while on rough surfaces, treatment dose-dependently decreased enzyme specific activity. Indomethacin treatment had either no effect or a slightly inhibitory effect on [3H]-thymidine incorporation on all surfaces. In contrast, indomethacin inhibited ALP on smooth surfaces and stimulated ALP on rough. Taken together, the results indicate that both AA and PGE2 influence osteoblast response by promoting osteoblast differentiation on smooth surfaces, while inhibiting it on rough surfaces. Because implants with rough surfaces are acknowledged to be superior to those with smooth surfaces, these results suggest that use of nonsterioidal anti-inflammatory drugs to block PGE2 production and reduce inflammation may be beneficial in the postoperative period after implant placement. They also indicate that manipulation of the AA metabolic pathway may offer a new therapeutic approach for modulating bone healing after implant placement. Because peri-implant healing takes place in a complex cellular environment quite different from the one used in the present study, additional work will be necessary to substantiate these possibilities.

Sticking ability in Spix's disk-winged bat, Thyroptera tricolor (Microchiroptera: Thyropteridae)

2001 ◽  
Vol 79 (12) ◽  
pp. 2261-2267 ◽  
Author(s):  
Daniel K Riskin ◽  
M Brock Fenton
Keyword(s):  
Rough Surfaces ◽  
The Other ◽  
Smooth Surfaces ◽  
Wet Adhesion ◽  
Porous Aluminum ◽  
Porous Sheet ◽  
Sheet Aluminum ◽  
Thyroptera Tricolor

Roosting Spix's disk-winged bats, Thyroptera tricolor, use disks on their wrists and ankles to cling to smooth leaves. In 584 trials we tested the ability of 31 T. tricolor and 121 other bats lacking disks (461 trials with 18 species from three families) to adhere to (i) medium-grade sandpaper, (ii) Lexan polycarbonate, (iii) solid sheet aluminum, and (iv) porous sheet aluminum. While T. tricolor readily adhered to smooth surfaces, the other species did not. Thyroptera tricolor did not show the same ability to adhere to rough surfaces as the other species that were tested. As was demonstrated by their performance on porous aluminum and sandpaper, the disks of T. tricolor worked by suction and sometimes by wet adhesion. In the course of adapting to adhere to smooth surfaces, T. tricolor appear to have lost some ability to roost on rough ones, although one adult T. tricolor climbed on a screen covering the inside walls of the polycarbonate cage by interlocking its thumb claws with the surface.

scholarly journals Prediction of the adhesive behavior of bio-inspired functionally graded materials against rough surfaces

AIP Advances ◽  
2014 ◽  
Vol 4 (6) ◽  
pp. 067143 ◽  
Author(s):  
Chen Peijian ◽  
Peng Juan ◽  
Zhao Yucheng ◽  
Gao Feng
Keyword(s):  
Functionally Graded Materials ◽  
Rough Surfaces ◽  
Functionally Graded ◽  
Graded Materials

scholarly journals MULTIPLE-PRIMITIVES-BASED HIERARCHICAL CLASSIFICATION OF AIRBORNE LASER SCANNING DATA IN URBAN AREAS

2017 ◽  
Vol XLII-2/W7 ◽  
pp. 837-843
Author(s):  
H. Ni ◽  
X. G. Lin ◽  
J. X. Zhang
Keyword(s):  
Urban Areas ◽  
Laser Scanning ◽  
Rough Surfaces ◽  
Hierarchical Classification ◽  
Airborne Laser Scanning ◽  
Smooth Surfaces ◽  
Airborne Laser ◽  
Individual Point ◽  
Point Cloud Segmentation ◽  
Third Stage

A hierarchical classification method for Airborne Laser Scanning (ALS) data of urban areas is proposed in this paper. This method is composed of three stages among which three types of primitives are utilized, i.e., smooth surface, rough surface, and individual point. In the first stage, the input ALS data is divided into smooth surfaces and rough surfaces by employing a step-wise point cloud segmentation method. In the second stage, classification based on smooth surfaces and rough surfaces is performed. Points in the smooth surfaces are first classified into ground and buildings based on semantic rules. Next, features of rough surfaces are extracted. Then, points in rough surfaces are classified into vegetation and vehicles based on the derived features and Random Forests (RF). In the third stage, point-based features are extracted for the ground points, and then, an individual point classification procedure is performed to classify the ground points into bare land, artificial ground and greenbelt. Moreover, the shortages of the existing studies are analyzed, and experiments show that the proposed method overcomes these shortages and handles more types of objects.

scholarly journals A comparison of tarsal morphology and traction force in the two burying beetles Nicrophorus nepalensis and Nicrophorus vespilloides (Coleoptera, Silphidae)

2019 ◽  
Vol 10 ◽  
pp. 47-61 ◽  
Author(s):  
Liesa Schnee ◽  
Benjamin Sampalla ◽  
Josef K Müller ◽  
Oliver Betz
Keyword(s):  
Rough Surfaces ◽  
Traction Force ◽  
Interspecific Difference ◽  
Smooth Surfaces ◽  
Burying Beetle ◽  
Surface Polarity ◽  
Traction Forces ◽  
Interspecific Differences ◽  
Friction Performance ◽  
The Impact

Our aim was to compare friction and traction forces between two burying beetle species of the genus Nicrophorus exhibiting different attachment abilities during climbing. Specifically, the interaction of adhesive hairs and claws during attachment with respect to various surface properties was investigated by using a 2 × 3 experimental design. Traction force was measured for two different surface energies (hydrophilic vs hydrophobic) varying in roughness from smooth to micro-rough to rough. Nanotribometric tests on single legs were also performed. The external morphology of the attachment devices investigated by scanning electron microscopy suggested higher intra-specific (intersexual) than inter-specific differences. Whereas differences between the two species in traction force were high on smooth surfaces, no differences could be detected between males and females within each species. With claws intact, both species showed the highest forces on rough surfaces, although N. nepalensis with clipped claws performed best on a smooth surface. However, N. nepalensis beetles outperformed N. vespilloides, which showed no differences between smooth and rough surfaces with clipped claws. Both species demonstrated poor traction forces on micro-rough surfaces. Results concerning the impact of surface polarity were inconclusive, whereas roughness more strongly affected the attachment performance in both species. Nanotribometric analyses of the fore tarsi performed on micro-rough and rough surfaces revealed higher friction in the proximal (pull) direction compared with the distal (push) direction. In these experiments, we detected neither differences in friction performance between the two species, nor clear trends concerning the influence of surface polarity. We conclude that the investigated morphological traits are not critical for the observed interspecific difference in attachment ability on smooth surfaces. Furthermore, interspecific differences in performance are only clear on smooth surfaces and vanish on micro-rough and rough surfaces. Our results suggest that even subtle differences in the adhesion-mediating secretion in closely related species might result in qualitative performance shifts.

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