Fabrication of Biomimetic Water Strider Legs Covered with Setae

Water striders have remarkable water-repellent legs that enable them to stand effortlessly and move quickly on water.Fluid physics indicates this feature is due to a surface-tension effect caused by the special hierarchical structure of the legs,which are covered with a large number of inclined setae with fine nanogrooves inducing water resistance.This inspires us to fabricate special water-repellent structure on functional surfaces through the cooperation between the surface treatment and the surface micro-and nanostructures,which may bring great advantages in a wide variety of applications.In this paper we present a procedure for fabricating biomimetic water strider legs covered with setae using Polycarbonate Track-Etched(PCTE)membranes as templates.By choosing appropriate membrane lengths,diameters,pitches and densities of the setae,the biomimetic legs can be fabricated conveniently and at a low cost.Furthermore we investigated the relationship between stiffness of the molding materials,high aspect ratio and density,which affect the fidelity of fabrication and self adhesion,to optimize the stability of setae.The knowledge we gained from this study will offer important insights into the biomimetic design and fabrication of water strider setae.

A Four-legged Wall-climbing Robot with Spines and Miniature Setae Array Inspired by Longicorn and Gecko

In industrial applications,climbing robots are widely used for climbing and detection of rough or smooth pipe surfaces.Inspired by the special claws of longicorn is that can crawl on rough surfaces and the array of tiny bristles of geckos that can crawl on smooth surfaces,a new type of wall-climbing robot for rough or smooth surfaces is proposed in this paper.The bionic palms of the robot are suggested with special bionic hooks inspired by the longicorn and bionic adhesive materials inspired by the gecko with a good performance on adhering on the surfaces.The special bionic hooks are manufactured by the 3D printing method and the bionic adhesive materials are made by the polymer print lithography technology.These two different bionic adhere accessory are used on the robot’s palm to achieve climbing on the different surfaces.This foldable climbing robot can not only bend its own body to accommodate the cylindrical contact surfaces of different diameters,but also crawl on vertical rough and smooth surfaces using their bionic palms.

Comparative studies on the structure and adhesion of setae in G. gecko and G. swinhonis

Scanning electron microscopy (SEM) and histological techniques were used to observe and study the setae structures of two gecko species (G. gecko and G. swinhonis) and the relationships between these structures and the adhesive forces. The SEM results showed that the setae of these two species were densely distributed in an orderly fashion, and branched with curved tips. The setae of G. gecko had cluster structures, each cluster containing 4-6 setae whose terminal branches curved towards the center of the toes at ~ 10o, the tips of the branches like spatulae and densely arrayed at an interval of less than 0.2―0.3 μm. On the contrary, the branch tips in the setae of G. swinhonis were curled, and the terminal parts of setae curved towards the center of the toes at various angles. Usually the setae of these gecko species branch twice at the top at intervals greater than that of G. gecko. The histological observation found that inside the setae of these two species there were plenty of unevenly distributed contents, such as epithelia, fat cells, pigmental cells and muscle tissue, but no gland cells existed. The results of functional experiments suggested that modifying the structure of gecko’s setae could reduce its adhesive ability dramatically, demonstrating the positive correlation between the structure of the gecko’s setae and its adhesive ability. The above results provide important information in designing bio-mimic setae and bio-gecko robots.

Biomechanism of adhesion in gecko setae

The study of the adhesion of millions of setae on the toes of geckos has been advanced in recent years with the emergence of new technology and measurement methods. The theory of the mechanism of adhesion by van der Waals forces is now accepted and broadly understood. However, this paper presents limitations of this theory and gives a new hypothesis of the biomechanism of gecko adhesion. The findings are obtained through measurements of the magnitude of the adhesion of setae under three different conditions, to show the close relationship between adhesion and status of the setae. They are reinforced by demonstrating two setal structures, follicle cells and hair, the former making the setae capable of producing bioelectrical charges, which play an important role in attachment and detachment processes. It is shown that the abundant muscular tissues at the base of the setae cells, which are controlled by peripheral nerves, are instrumental in producing the foot movement involved in attachment and detachment. Our study will further uncover the adhesion mechanism of geckos, and provide new ideas for designing and fabricating synthetic setae.

Size and dispersion of urticating setae in three species of processionary moths

Larvae of the processionary moths of the Palaearctic region bear urticating setae that are released against ver­tebrate predators,especially insectivorous birds.A few species are pests of forest and urban trees and,conse­quently,may threaten human and animal health during outbreaks,causing dermatitis,conjunctivitis and respira­tory distress.Although some studies provide detailed information about the setae,particularly those of the pine processionary moth Thaumetopoea pityocampa,there is little knowledge on the morphological traits of the setae and their release by the larvae.In the present study we identify major traits of the setae of 3 species of proces­sionary moth,T.pityocampa,T.pinivora and T.processionea,which are potentially helpful in the understanding of setae dynamics in the environment:(i)diameter and length of setae and(ii)analysis of dynamical properties of the setae in the airborne state.Setae are highly variable in size,with bimodal distribution in T.pityocampa and T.pinivora;in these 2 species,short and long setae are interspersed within the integument fields where they occur.The difference in the seta size has important consequences in dispersion,as smaller setae can spread 5 times further than their bigger counterparts.This information is relevant for a full understanding of the defen­sive importance of larval setae against natural enemies of the processionary moths,as well for elucidating the importance of the processionary setae as air pollutants,both close to the infested trees and at longer distances.

Water Striders:The Biomechanics of Water Locomotion and Functional Morphology of the Hydrophobic Surface(Insecta:Hemiptera-Heteroptera)

Water striders are insects living on the water surface, over which they can move very quickly and rarely get wetted. We measured the force of free walking in water striders, using a hair attached to their backs and a 3D strain gauge. The error was calculated by comparing force and data derived from geometry and was estimated as 13%. Females on average were stronger （1.32 mN） than males （0.87 mN）, however, the ratio of force to weight was not significantly different. Compared with other lighter species, Aquarius paludum seems stronger, but the ratio of force to weight is actually lower. A. paludum applies about 0.3 mN.cm^-1 to 0.4 mN.cm 1 with its mid-legs, thus avoiding penetrating the surface tension layer while propelling itself rapidly over the water surface. We also investigated the external morphology with SEM. The body is covered by effectively two layers of macro-and micro-hairs, which renders them hydrophobic. The setae are long （40 μm-60μm） and stiff, being responsible for waterproofing, and the microtrichia are much smaller （〈10μm）, slender, and flexible, holding a bubble over the body when submerged.

External Morphology and Ultrastructure of Tegumental Glands of Aegla platensis(Crustacea,Anomura,Aeglidae)Pleopods:Might They Play A Role in Egg Attachment?

Egg incubation on the female abdomen is the parental care behavior observed in aeglids,in which eggs are kept adhered to maternal pleopods and maintained,cleaned and aerated.In A.platensis,egg attachment occurs with the aid of pleopodal setae,which are twisted around their axis in the distal region,forming the funiculus,and pleopodal glands,which are responsible for the production of the adhesive substance that seems to be involved in egg fixation to pleopodal setae.Those glands are acini formed by secretory cells arranged concentrically around a central duct,giving them a rosette appearance.Two types of secretory cells were observed,those that produce electron-lucid vesicles and those having electron-dense ones.Both kinds of vesicles are released in a duct whose opening pore is located on the pleopodal surface and constitute the adhesive substance that coats eggs and pleopodal setae,ensuring egg fixation to the female body and maternal care maintenance.This study investigates the internal and external morphology of Aegla platensis pleopods,to understand the egg attachment process and identify the structures involved in this phenomenon.Three microscopy techniques are used:scanning electron microscopy(SEM),transmission electron microscopy(TEM),and optical microscopy(OM).

Restudies on Body Surface of Dung Beetle and Application of Its Bionics Flexible Technique

A scanning electron microscope was used to observe the structures of the setae on the surface of a dung beetle Copris ochus, Motschulsky. There are lots of setae on the body surface, especially on the ventral part surface and lateral to the legs which are different in size, arrangement and shape. These setae have different lengths and many thorns on the whole seta. The top ends of these setae stand up without furcations which direct uprightly towards the surface of the touched soil. By the method of removing these setae, getting the insect weight before and after digging into the dung we affirm farther that the setae on the beetle body surface form the anti-stick and non-adherent gentle interface. The soil machines and components made by imitating the gentle body surface of beetles have favorable non-adherent results.

Effects of hysteresis of static contact angle (HSCA) and boundary slip on the hydrodynamics of water striders

It is known that contact lines keep relatively still on solids until static contact angles exceed an interval of hysteresis of static contact angle (HSCA), and contact angles keep changing as contact lines relatively slide on the solid. Here, the effects of HSCA and boundary slip were first distinguished on the micro-curvature force (MCF) on the seta. Hence, the total MCF is partitioned into static and dynamic MCFs correspondingly. The static MCF was found proportional to the HSCA and related with the asymmetry of the micro-meniscus near the seta. The dynamic MCF, exerting on the relatively sliding contact line, is aroused by the boundary slip. Based on the Blake-Haynes mechanism, the dynamic MCF was proved important for water walking insects with legs slower than the minimum wave speed . As insects brush the water by laterally swinging legs backwards, setae on the front side of the leg are pulled and the ones on the back side are pushed to cooperatively propel bodies forward. If they pierce the water surface by vertically swinging legs downwards, setae on the upside of the legs are pulled, and the ones on the downside are pushed to cooperatively obtain a jumping force. Based on the dependency between the slip length and shear rate, the dynamic MCF was found correlated with the leg speed U, as , where and are determined by the dimple depth. Discrete points on this curve could give fitted relations as (Suter et al., J. Exp. Biol. 200, 2523-2538, 1997). Finally, the axial torque on the inclined and partially submerged seta was found determined by the surface tension, contact angle, HSCA, seta width, and tilt angle. The torque direction coincides with the orientation of the spiral grooves of the seta, which encourages us to surmise it is a mechanical incentive for the formation of the spiral morphology of the setae of water striders.

Recent advances in gecko adhesion and friction mechanisms and development of gecko-inspired dry adhesive surfaces

The remarkable ability of geckos to climb and run rapidly on walls and ceilings has recently received considerable interest from many researchers.Significant progress has been made in understanding the attachment and detachment mechanisms and the fabrication of articulated gecko-inspired adhesives and structured surfaces.This article reviews the direct experiments that have investigated the properties of gecko hierarchical structures,i.e.,the feet,toes,setae,and spatulae,and the corresponding models to ascertain the mechanical principles involved.Included in this review are reports on gecko-inspired surfaces and structures with strong adhesion forces,high ratios of adhesion and friction forces,anisotropic hierarchical structures that give rise to directional adhesion and friction,and“intelligent”attachment and detachment motions.

The Morphology and Reciprocation Movement of Honeybee＇s Hairy Tongue for Nectar Uptake

A honeybee uses its brush-like tongue （glossa） to dip nectar and the setae densely distributed on it can increase the amount of trapped nectar observably. The glossa is often simplified as a cylinder covered by uniformly distributed and vertically erected setae during the drinking process, herein variations of the dimensions together with the erection angles of glossal setae are assumed to be negligible. In this paper, a dynamic model for the glossa retraction phase under the specific erection pattern of glossal setae is established, and the energy saving mechanism is extensively studied by comparing four types of erection pat- terns. Then the theoretically-optimal configuration, which satisfies the minimum energy consumption, is achieved from the dynamic model. Using the scanning electron microscope and a specially-designed high-speed camera system, we measure the dimensions of the glossal satae and capture dynamics of the hairy glossa in nectar feeding. It is proven that the erection angle of the glossal setae varies along the tongue axis, which shows a high concordance with our theoretically-optimal configuration. Compared with the hypothetical uniform distribution mode of glossal setae proposed by former researchers, we obtain a 16% increase in energy saving from actual erection pattern.