Functional surface microstructures inspired by nature – From adhesion and wetting principles to sustainable new devices

Arzt, Eduard; Quan, Haocheng; McMeeking, Robert M.; Hensel, René

doi:10.1016/j.pmatsci.2021.100823

Cited by 155 publications

(88 citation statements)

References 466 publications

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“…Tribological problems from the latter areas are assigned to biotribology. It deals, for example, with human joint prosthesis, dental implants, bio-inspired adhesives, or friction-based surface haptics technologies [1][2][3][4]. Due to the multiscale roughness and a multitude of additional effects such as lubrication, adhesion or wear, such problems, if possible at all, can only be solved by full computational methods.…”

Section: Introductionmentioning

confidence: 99%

An Analytical Model for Almost Conformal Spherical Contact Problems: Application to Total Hip Arthroplasty with UHMWPE Liner

Heß

Forsbach

2021

Applied Sciences

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Due to its high relevance for designing ball joints in mechanical engineering and (artificial) hip joints in biomechanics, the almost conformal elastic contact between a sphere and a spherical cup represents an important contact problem of current research. As no closed-form analytical solution to the problem has been found to date, full computational methods such as the finite element method are needed for analysis. However, they often require incredibly long, unacceptable calculation times, making parameter studies hardly practicable. For this reason, approximate analytical and semi-analytical models are applied, capable of predicting quantities of interest with sufficient accuracy. In the present work, a very simple model based on a radially directed Winkler foundation is presented, which provides (approximate) closed-form analytical solutions for both the pressure distribution and the dependencies between macroscopic contact quantities such as normal force and indentation depth. To ensure an optimal mapping of a specific contact problem, only the foundation modulus must be defined in a suitable way. As an example, the proposed model has been successfully adapted to adequately simulate the frictionless normal contact for hard-on-soft hip implants. For this purpose, the foundation modulus was approximated with the aid of a finite element analysis instead of adopting it from already well-established models, as the latter produce clearly erroneous results for large liner thicknesses and large Poisson’s ratios. By a comparison with extensive parameter studies of finite element simulations, it is demonstrated that the proposed model provides acceptable results for all commonly used hard-on-soft hip implants. On this basis, the influence of geometrical changes of the femoral head and the acetabular cup on the maximum pressure as well as the half-contact angle is discussed, and consequences on the wear behavior are deduced.

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Section: Introductionmentioning

confidence: 99%

An Analytical Model for Almost Conformal Spherical Contact Problems: Application to Total Hip Arthroplasty with UHMWPE Liner

Heß

Forsbach

2021

Applied Sciences

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“…These attachments are required in various medical and industrial applications such medical patches ( 4 ), tissue engineering, or underwater soft robotics ( 5 , 6 ). Microfibrillar designs, which produce reliable adhesion in the dry state ( 7 ), are useful under wet conditions only after displacing water from the contact zone: Tried strategies are hydrophobic designs ( 8 , 9 ), direct chemical bonding ( 10 ), or dynamic bonds in tough hydrogels ( 11 ). These solutions limit the variability of the counter surface and suffer from drawbacks related to durability or swelling.…”

Section: Introductionmentioning

confidence: 99%

Water as a “glue”: Elasticity-enhanced wet attachment of biomimetic microcup structures

Wang

Elhebeary

et al. 2022

Sci. Adv.

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Octopus, clingfish, and larva use soft cups to attach to surfaces under water. Recently, various bioinspired cups have been engineered. However, the mechanisms of their attachment and detachment remain elusive. Using a novel microcup, fabricated by two-photon lithography, coupled with in situ pressure sensor and observation cameras, we reveal the detailed nature of its attachment/detachment under water. It involves elasticity-enhanced hydrodynamics generating “self-sealing” and high suction at the cup-substrate interface, converting water into “glue.” Detachment is mediated by seal breaking. Three distinct mechanisms of breaking are identified, including elastic buckling of the cup rim. A mathematical model describes the interplay between the attachment/detachment process, geometry, elasto-hydrodynamics, and cup retraction speed. If the speed is too slow, then the octopus cannot attach; if the tide is too gentle for the larva, then water cannot serve as a glue. The concept of “water glue” can innovate underwater transport and manufacturing strategies.

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“…Bio-inspired adhesives are an important area of biomimetic innovation 1 . However, despite significant progress [2][3][4] , key challenges remain. Technical adhesives often need to cover large areas and carry heavy loads, resulting in a classic scaling problem: large contacts suffer reduced strength due to stress concentrations, and heavy weights lead to poorer relative performance due to changes in the support-surface-to-volume ratio 4,5 .…”

Section: Introductionmentioning

confidence: 99%

The physical properties of the stick insect pad secretion are independent of body size

Kaimaki

Andrew

Attipoe

et al. 2022

Preprint

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Many insects use adhesive organs to climb. The ability to cling to surfaces is advantageous but is increasingly challenged as animals grow, due to the associated reduction in surface-to-volume ratio. Previous work has demonstrated that some climbing animals overcome this scaling problem by systematically altering the maximum force per area their adhesive pads can sustain; their adhesive organs become more efficient as they grow, an observation which is also of substantial relevance for the design of bio-inspired adhesives. What is the origin of this change in efficiency? In insects, adhesive contact is mediated by a thin film of a liquid, thought to increase adhesive performance via capillary and viscous forces. Here, we use interference reflection microscopy and dewetting experiments to measure the contact angle and dewetting speed of the pad secretion of Indian stick insects varying in mass by over two orders of magnitude. Neither contact angle nor dewetting speed change significantly with body mass, suggesting that the key physical properties of the pad secretion - its surface tension and viscosity - are size-invariant. Thus, the observed change in pad efficiency is unlikely to arise from systematic changes of the physical properties of the pad secretion; the functional role of the secretion remains unclear.

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Functional surface microstructures inspired by nature – From adhesion and wetting principles to sustainable new devices

Cited by 155 publications

References 466 publications

An Analytical Model for Almost Conformal Spherical Contact Problems: Application to Total Hip Arthroplasty with UHMWPE Liner

An Analytical Model for Almost Conformal Spherical Contact Problems: Application to Total Hip Arthroplasty with UHMWPE Liner

Water as a “glue”: Elasticity-enhanced wet attachment of biomimetic microcup structures

The physical properties of the stick insect pad secretion are independent of body size

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